R:\typeset\brn13-3\300889.vp

Brain Topography, Volume 13, Number 3, 2001 Proceedings
ISBET 2000: The 11th World Congress of the International
Society for Brain Electromagnetic Topography,
Germany
November 16-19, 2000
Organizer: Maurer and Dierks
In contrast, the parietal P300 source strength increased af- Low-Resolution Brain Electromagnetic Tomography
ter acute (day 1), subacute and superimposed infusion (LORETA) of Cognitive Event-Related Potentials in
(day 15) of Actovegin as compared to placebo.
Age-Associated Memory Impairment and Effects of
Nootropic Drug Therapy. - P. Anderer*, H.V.
Some Advances in MEG and EEG Source Imaging
Semlitsch*, B. Saletu*1 and R.D. Pascual-Marqui+
Methods. - S. Baillet (Cognitive Neuroscience and
(*Department of Psychiatry, University of Vienna,
Brain Imaging Laboratory, Hôpital de la Salpêtrièr,
Austria and +The KEY Institute for Brain-Mind Re-
Paris, France).
search, Department of Psychiatry, University Hospital,
Most of the approaches to MEG and EEG source esti- Switzerland).
mation can be reduced to 1) parametric techniques con- Cognitive event-related potentials were recorded in sisting in the localization of discrete equivalent source an auditory two-tone paradigm in 43 patients aged 51-79 models like current dipoles and 2) imaging techniques years with the diagnosis of age-associated memory im- that produce estimates of the cortical current density, pairment (AAMI). Eighteen patients participated in a dou- usually given anatomical information from the MRI.
ble-blind, placebo-controlled study on the effects of Parametric approaches to MEG/EEG source localization Actovergin®, a protein-free metabolically active can rapidly generate a physical model of neural current hemoderivative improving oxygen and glucose utiliza- generators using a limited number of parameters. How- tion. Low-resolution brain electromagnetic tomography ever, physiological interpretation of these models is of- (LORETA) revealed medial (frontal and parietal) and lat- ten difficult. Image-based approaches to the inverse eral (dorso- and ventrolateral prefrontal, middle/superior problem provide a direct estimate of cortical current gen- temporal, posterior superior temporal/inferior parietal) erators, but computationally expensive non-linear meth- P300 sources. Significant reductions in LORETA source ods are required to produce focal sources. We will review strength in AAMI were mainly found medially frontally, some of the basic principles related to both of these ap- right dorsolaterally prefrontally and right inferiorly proaches and will present some recent advances for a parietally. Since these anatomically highly interconnected better characterization of the sources of the MEG/EEG.
brain regions in the right hemisphere are part of a network This includes the quantification of the spatial extension associated with sustained attention, the results speak for a of the cortical areas involved by cortical remapping decline in attentional resource capacity in AAMI patients.
through a multi-step approach involving discrete mod-els for the sources and their cortical counterparts usingnon-linear imaging constraints. We will also present Copyright 2001 Human Sciences Press, Inc.
some application of multi-resolution cortical imaging techniques. We will finally discuss about the challenge of tency did not differ between HD and control children.
comparing and possibly combining an f-MRI analysis LORETA source solutions revealed posterior P300 sources which were attenuated in HD children.
Conclusions: Covert attention to cues preceding po- Slow Cortical Potential Manifestations of Anticipatory
tential targets is already impaired in HD, determines Fear and Attention. - K.B.E. Böcker*, J.M.P. Baas*, M.N.
performance with subsequent targets, and activates the Verbaten* and H.M. Huizenga+ (*Utrecht University,
posterior brain. These findings extend previous results Department of Psychopharmacology, The Nether-
obtained for children with Attention Deficit Hyperactiv- lands, +University of Amsterdam, Department of Psy-
ity Disorder and demonstrate the usefulness of clinical chology, The Netherlands).
multicenter studies using cognitive brain mapping.
The Contingent Negative Variation (CNV) is usu- ally recorded in experimental tasks which induce motor Evoked and Induced EEG Responses Under Median
preparation. The non-motor CNV, or Stimulus Preceding Nerve Stimulation. - A. Brovelli*, E. Daprati*, R.J.
Negativity (SPN), is most readily observed in S1-S2 para- Naranjo*, A. Muzur*, R. Budai+ and P.P. Battaglini*^ (*
digms involving the presentation of S2 stimuli with af- SISSA-ISAS, Cognitive Neuroscience Sector, Trieste,
fective valence. The SPN indeed manifested itself in a Italy, +Neurology Unit, Dept. of Neuroscience, OSMM,
previous study which employed the anticipatory fear Udine, ^B.R.A.I.N. Centre for Neuroscience, Dept. of
paradigm.The present study intended to compare antici- Physiology and Pathology, University of Trieste, Italy).
patory fear (S2 = shock) and anticipatory attention (S2 = Two main categories of EEG responses can be identi- to-be-counted weak vibration). Experimental conditions fied: evoked and induced. The present study aims at in- were otherwise equal. The S1-S2 interval was 1.2 - 1.4 s.
vestigating the relationship between evoked and Preliminary results (N=7) show that the SPN (measured induced responses after median nerve stimulation. Scalp at FCz) was significant in both the anticipatory fear (-4.8 EEG was recorded using a 32-channel system on 4 volun- ± 2.0 µV) and the anticipatory attention (-2.5 ± 1.0 µV) teers under medial nerve stimulation and integrated conditions. However, the latter difference between the with anatomical MRI data. Methods based on wavelet two anticipatory conditions was not statistically signifi- and Hilbert transform allow the computation of a cant. Details on the topographical distribution of the SPN time-frequency (TF) representation of the instantaneous in both conditions will be presented.
amplitude of a signal. TF representations of the instanta-neous amplitude averaged across trials and the TF repre- Multicenter P300 Brain Mapping of Inattention to Cues
sentation of the instantaneous amplitude of averaged i n H y p e r k i n e t i c C h i l d r e n . - D . B r a n d e i s , T .
evoked potentials were computed so to extract the Banaschewski*, L. Baving~, P. Georgiewa+, B. Blanz+,
evoked + induced and evoked responses, respectively.
M.H. Schmidt~, A. Warnke^, H.C. Steinhausen, A.
An induced mean amplitude increase in the beta band Rothenberger* and P. Scheuerpflug^ (Departments of
was found approximately 500 msec after stimulation Child and Adolescent Psychiatry Universities of
over the controlateral somatosensory area, whereas an Zürich, *Göttingen, +Jena, ^Würzburg, ~ Central Insti-
alpha band decrease was found over extended regions.
tute for Mental Health, Mannheim).
Preliminary results are presented and discussed accord- Objective: Multicentric 19-channel EP brain mapping data was recorded from children with and without hyperkinetic disorders (HD) during a cued continuous per-formance test (CPT) to examine attentional P300 effects for EEG Source Identification Related to a Frequency
deficits in HD children and for consistency across clinics.
Band: 3D Located Fluvoxamine Effects During REM
Method: CPT performance and P300 maps to cues Sleep. - A. Coatanhay, L. Soufflet, L. Staner, M.
and distractors from 148 children were tested for differ- Toussaint, P.H. Boeijinga and J.-P. Macher(FORENAP
ences between age- and sex-matched groups with and - Centre Hospitalier - Rouffach - France).
without HD (N=57 each), and between clinics (N=5).
We have developed a methodology, based on the Results: Consistency of performance, P300 mea- LORETA (Low Resolution Tomography) algorithm, to sures, and amplitude increases plus topographic solve inverse EEG problems related to a frequency band.
changes for P300 maps to cues compared to distractors We have studied the EEG source localisation during was established across most clinics. HD children missed REM sleep (paradoxical sleep) for four frequency bands: more targets, made more false alarms, and had larger N1 delta (0.5-3.5Hz), theta (4-7.5Hz), alpha (8-12.5Hz) and and smaller P3b map amplitudes after cues than control children. Cue-P300 amplitude correlated positively with Our study compared EEG source localisation for detecting subsequent targets. P300 topography and la- each frequency band before and after one week of treat- ment with the antidepressant fluvoxamine (100 mg).
ally identified with eyeblink and other artifacts. One Subjects were 9 young (25.8 ±6.6 years old) healthy vol- component clearly represented the spike and sharp wave unteers. EEG was recorded using 21 electrodes based on activity. The EEG was reconstructed with only this com- ponent present, and subjected to single dipole modeling.
EEG activity was reduced during REM sleep after The residual variance over the entire epoch was lower the fluvoxamine treatment in all frequency bands. In ad- than that of any single, unaveraged spike or sharp wave dition, tomographic data evidenced that modification selected from the original recording. Thus ICA, with no a seems different between high (theta, alpha, beta) and low priori dipole assumptions, was able to extract a very di- (delta) frequencies. The reduction was more significant pole-like spatiotemporal component from raw EEG.
(Student test p<0.05) in the right inferior parietal lobe forlow frequencies and in the central occipital cortex for Frequency Domain EEG Source Locations During Arm
Levitation Under Hypnosis: A Pilot Study. - P.L. Faber,
P. Wohlgemuth, L.R.R. Gianotti and D. Lehmann (The
Topographic EEG Alterations in Cognitive Impair-
KEY Institute for Brain-Mind Research, University
ment. - T. Dierks*+, V. Jelic^, L. Frölich+, L.O.
Hospital of Psychiatry, Zurich, Switzerland).
Wahlund^ and K.Maurer+ (*Dept. of Psychiatric
27-channel EEG was recorded from 4 right-handed Neurophysiology, University Hospital of Clinical Psy-
subjects during 2 conditions: left arm raised under hyp- chiatry Bern, Switzerland, +Dept. of Psychiatry, Univ.
notic suggestion, and left arm raised on command before of Frankfurt, Germany, ^Alzheimer Research Center,
and after hypnosis. Locations of intracerebral 3-D source Karolinska Institute, Stockholm, Sweden).
gravity centers of seven independent EEG frequency Many EEG parameters like peak frequency, the bands were computed (using FFT-Dipole- Approxima- amount of slow wave and alpha activity are abnormal tion) for each 2-second analysis epoch (total 324), and av- and correlate with the severity of cognitive functions in eraged over epochs for each condition and subject.
Alzheimer Disease (AD). However, due to technical limi- Exploratory statistics (two-tailed paired t-tests, N=4 sub- tations conventional frequency analysis does not allow to jects) showed significant differences of source locations draw any conclusions about spatial pattern of cerebral between conditions for delta (1.5-6Hz), alpha1 pathophysiology. We have quantified spatial EEG alter- (8.5-10Hz), beta1 (12.5-18Hz) and beta2 (18.5-21Hz). Un- ations in around 200 patients suffering from Alzheimer der hypnosis, delta was more posterior, alpha1 more left, disease and cognitive impairment using novel analysis beta1 more anterior, and beta2 more right. Disregarding lateralizations (no right arm data!), the results indicate (FFT-approximation and adaptive segmentation). In AD that during hypnotic arm levitation, along the ante- patients, a shift of alpha- and beta-EEG generators and rior-posterior brain axis, inhibitory activity (delta) center of gravity of the microstate topography towards shifted to more posterior areas but excitatory activity frontal brain regions was observed. The amount of this shift correlated with the degree of dementia. The Grant #670806 from Institut für Grenzgebiete der anteriorization of EEG-generators and microstates reflect the pathological spatial pattern of glucose metabolism inAD. A similar spatial pattern of EEG-alterations could be Cannabis-Induced Topographic Changes in Pre/Post
found in asymptomatic family members with genetic AD.
EEG Activity During Rest and Music Perception. - J.
Fachner*, D. Aldridge* and E. David+ (*Institute for
Dipole Modeling of an Epileptiform Component Ex-
Music Therapy, UW/H, +Institute of Physiology,
tracted by Independent Component Analysis of 128
Channel EEG. - K.J. Eriksen*, K.E. Karnofski+ and C.
In scientific literature cannabis is found to change or Davey+ (*Legacy Good Samaritan Hosp, Portland, OR,
enhance time-, space-, body- and movement perception, +Electrical Geodesics, Inc, Eugene, OR).
emotion, imagery and association patterns. Presented Independent Component Analysis (ICA) is a tech- here is an explorative study on Cannabis and Music Per- nique for separating mixed, statistically independent ception, conducted in a qualitative and quantitative way spatiotemporal signal components. We wished to exam- in a habituated setting. EEG-Brainmapping Data (rest; ine whether it could remove background "brain noise" pre/post listening; 28 EEG traces; smoked Cannabis φ 20 from unaveraged epileptiform activity as a preprocess- mg D9 THC) were averaged and treated with a T-test and ing step prior to source analysis. ICA was applied to 128 channel EEG data obtained from a patient with right Compared to pre-THC-rest and pre-THC-Music in fronto-temporal spikes and confounding eyeblinks. We the post-THC-Music-EEG a rise of Alpha percentage and obtained 128 components, some of which could be visu- power was observed in the parietal cortex on four sub- jects, while other frequencies decreased in power. De- guage processing was followed by a bifrontal creased amplitudes could represent a decreased hypooxygenation, which was interpreted as a relative cell-firing mode caused by cannbinoidreceptor mecha- prefrontal hypoperfusion due to a blood volume redistri- nism. Comparing pre/post music EEGs, differences bution in favor of language-related temporal brain areas.
(p<0.01) were found in the right frontotemporal cortex A visual control task did not affect the prefrontal concen- on Theta and on Alpha in the left occipital cortex.
trations of O2Hb and HHb at all. An investigation with a Changes in temporal and occipital areas and in- language-generation task (verbal fluency test) showed creasing a-signal strength in parietal association cortex an oxygenation overshoot in left prefrontal brain areas in seem to represent a neural correlate of altered music per- healthy controls consistent with the location of Broca’s ception and hyperfocusing on the musical time-space.
area, and a loss of this hemispheric asymmetry in pa- Alpha amplitude changes remind on "reverse Alpha" tients with Alzheimer‘s dementia. All these findings findings in studies with gifted individuals.
point to the ability of the non-invasive NIRS-method toassess task-specific patterns of physiological and Event-Related LORETA- and FMR-Imaging of Motor
Response Inhibition Converge to Anterior Cingulum
Activations. - A.J. Fallgatter, M.J. Herrmann, K.P.
Electrophysiological Measures Related to Impulsivity
Lesch, B. Hamelbeck and A.J. Bartsch (Dept. of Psychia-
and Serotonergic Neurotransmission. - A.J. Fallgatter
try, University of Wuerzburg, Germany).
and M.J. Herrmann (Dept. of Psychiatry, University of
Several investigations concluded that the anterior Wuerzburg, Germany).
cingulate gyrus (ACG) of the prefrontal cortex is involved Impulsivity is both, a very important feature in sev- in response inhibition. In our present study, this particular eral psychiatric conditions related to a low central brain function was elicited experimentally by a cued ver- serotonergic neurotransmission like aggressive behavior sion of the Continuous Performance Test (CPT). The CPT and suicidality, and a core symptom of frontal lobe syn- contains both, the execution (Go-condition) and inhibition dromes of various etiologies. ERP-parameters of re- (NoGo-condition) of prepared motor responses. Source sponse control elicited with the execution (Go-condition) analyses of event-related potentials by Low Resolution and the inhibition (NoGo-condition) of an anticipated Electromagnetic Tomography (LORETA) revealed signif- motor response within the Continuous Performance Test icant electrical ACG-hyperactivity during response inhi- might be suitable candidates for an objective measure- bitions. In addition, BOLD-contrast sensitive echo planar ment of impulsivity. The location of the brain electrical imaging (mosaic EPI on 1.5 T Vision scanner: TE = 60 ms, field in the NoGo-condition has been shown to be associ- RT = 2083 ms, FA = 78°, 17 interleaved slices, distance fac- ated with the presence of at least one short allele of the se- tor 0.25, 4 x 4 x 5 mm voxel size) provided the first rotonin transporter promoter and, therefore, with a event-related functional MRI data of healthy volunteers diminished serotonergic neurotransmission. The topo- performing the CPT. General linear modelling by Statisti- graphical ERP-parameters and the I7-impulsivity score cal Parametric Mapping (SPM 99) disclosed significant were determined in 22 healthy subjects. Impulsivity was BOLD-responses within the ACG for the NoGo-condition.
correlated with both, a more anterior location of the Go- Taken together, these findings indicate that simple motor (r = 0.58, p < 0.01) and the NoGo-centroid (r = 0.53, p = response inhibitions drive neuroelectrical and -metabolic 0.01). Therefore, these ERP-parameters may be candi- dates for the measurement of the brain electrical basis ofimpulsive behavior.
In Vivo Measurement of Human Brain Function with
NIRS. - A.J. Fallgatter*, W.K. Strik+, Th.J. Mueller+ and
Electrophysiological Indications for an Altered
M.J. Herrmann* (*Dept. of Psychiatry and Psychother-
Prefrontal Response Control in Schizophrenias. - A.J.
apy, University of Wuerzburg, Germany, +University
Fallgatter*, W.K. Strik+, Th.J. Mueller+ and M.J.
Hospital of Clinical Psychiatry, Bern, Switzerland).
Herrmann* (*Dept. of Psychiatry and Psychotherapy,
Near-Infrared Spectroscopy (NIRS) is a new University of Wuerzburg, Germany, +University Hos-
non-invasive optical method which allows an in vivo pital of Clinical Psychiatry, Bern, Switzerland).
measurement of the concentration changes of oxy- Prefrontal brain areas, in particular the anterior (O2Hb) and deoxyhemoglobin (HHb) in brain tissue. In cingulate gyrus (ACG), are supposed to be involved in the healthy controls NIRS revealed a bifrontal activation pat- pathophysiology of schizophrenic diseases. Recently, the tern during performance of a Wisconsin Card Sorting NoGo-anteriorisation (NGA) has been introduced as a Test, and a right prefrontal activation during the Contin- new electrophysiological measure of response control and uous Performance Test. This hemispheric asymmetry ACG-function. The NGA consists of a more anterior loca- was reduced in schizophrenic patients. Moreover, lan- tion of the brain electrical field in the event-related poten- tials of the NoGo- compared to the Go-condition elicited tial gradients from the inside to the outside of the head.
with a cued Continuous Performance Test (CPT). In 19 Thus, there is an optimum distribution of nodes to the chronic schizophrenic patients the NGA was significantly different boundaries, resulting in improved accuracy as reduced in comparison with age- and sexmatched healthy compared to standard uniform distributions for a given, controls (0.07 ± 0.74 vs. 0.90 ± 0.37 electrode distances; t = -4.36, p = 0.0001). On a qualitative level, 10 of 19 schizo- Spherical and realistically shaped surfaces were ap- phrenic subjects had no NGA, which was present in every proximated by 500, 1000, 2000, and 3000 nodes each lead- single healthy control (Chi-square (df = 1) 6.81, p < 0.01).
ing to 64 different BEM-models with 1500 to 9000 nodes in These results are interpreted as an electrophysiological ex- total. 81 electrodes were placed on an extended 10/20 sys- pression of disturbed ACG-function in schizophrenic pa- tem grid. Potential distributions of test-dipoles at 4000 tients. Subsequent studies will clarify the relationship of random positions were calculated. Dipoles were then fit- this electrophysiological parameter with distinct ted using 192 different BEM-models and mislocalizations psychopathological features, e. g. motor symptoms in were evaluated to find the optimum node distribution.
catatonic schizophrenias or flattening of affect and drivein hebephrenic schizophrenias.
Spatial Analysis of Brain Electrical Activity in Psychi-
atric Disorders. - S. Galderisi (Department of Psychia-
The Feasibility of Simultaneously FMRI and EEG Ex-
try, University of Naples SUN, Naples, Italy).
periments. - A. Federspiel, T.J. Müller, T. Dierks, T.
Most investigations involving spatial analysis of Koenig, D. Hubl and W.K. Strik (University Hospital of
brain electrical activity in psychiatric disorders, in anal- Clinical Psychiatry, Department of Psychiatric
ogy with empirical work carried out in neurological pa- Neurophysiology, Bern, Switzerland).
tients, have been looking for dysfunctional regions in Understanding the functioning of information pro- different psychopathological categories, trying to confirm cesses of the human brain requires the merge of knowledge findings provided by other brain imaging techniques. Ex- obtained from all possible fields involved in this topic. The amples of this approach include hypofrontality or abnor- physiological responses related to brain activation can be malities of temporal regions in schizophrenia and frontal dysfunctions in obsessive compulsive disorder.
level-dependent) fMRI. The spatial resolution obtained It will be argued that this approach does not fully ex- with this method is sufficient. The determination of the dy- ploit the potential resources of spatial analysis of brain namics of the brain activation is limited by the poor tempo- electrical activity, especially those related to its high tem- ral resolution, however. Electrophysiologic responses are poral resolution, i.e. information on spatiotemporal dy- best measured by means of EEG with temporal resolution in the subsecond range. The outcome of the combined fMRI Psychopathological phenomena involve abnormali- and EEG recording is thought to complement the picture of ties of the complex and dynamic interaction of several cog- physiologic processes. In the present study we present re- nitive processes, often show a waxing and waning nature sults of the simultaneously fMRI and EEG measurment of and sometimes may be induced by drug administration or visual evoked potential (VEP). In order to test the goodnes environmental manipulation. They seem to be better ac- of the EEG recording as a function of the magnetic environ- counted for by abnormalities of functional connectivity ment we repeaded the measurement under four different within largely distributed cortical networks, rather than conditions. Our results showed no changes in the ampli- the dysfunction of individual specialized regions.
tude and in the latency of the P100 (136 ms) during the gra- The study of the dynamic changes of spatial config- dient boost as compared to the absence of magnetic field.
urations in time and their relations to task demands The LORETA analysis of the positive P100 revealed the and/or state changes is more appropriate to promote our dominant source location in the region of V5 (MT).
understanding of neural mechanisms underlying psy-chiatric disorders and treatment interventions.
Optimized Node Distributions for Realistically
Shaped Boundary Element Method Volume Conductor
EEG Intracerebral Source Locations, LORETA Brain
Models. - M. Fuchs, M. Wagner and J. Kastner
Electric Tomography and MMSE in Alzheimer’s Dis-
(Neuroscan Labs, Lutterothstr. 28e, 20255 Hamburg,
ease. - L.R.R. Gianotti*+, D. Lehmann+, R.D.
Germany).
Pascual-Marqui+ and U. Schreiter Gasser* (*Division
The Boundary Element Method (BEM) approxi- of Geriatric Psychiatry, +The KEY Institute for
mates the different compartments of volume conductor Brain-Mind Research, University Hospital of Psychia-
models by closed triangle meshes with a limited number try, Zurich, Switzerland
of nodes. The shielding effect of the weakly conducting Brain electric activity (19-channel eyes-closed resting skull layer of the human head leads to decreasing poten- EEG) and Minimal Mental State Examination (MMSE) was recorded in nine patients suffering from Alzheimer type tex of a subject such that the assumed dipoles possess dementia (DAT) in two sessions, before and three months rather orthogonal orientation to each other. The retinotopic after onset of rivastigmine medication. For seven EEG fre- map of the subject provides the information about the cor- quency bands (delta, theta, alpha1&2, beta1, 2&3), the responding regions in the visual field which have to be stimulated in order to produce activity at the selected di- FFT-Dipole-Approximation) and the 3-dimensional distri- pole positions. We report about first results using a simple butions of current density (via Low Resolution Electromag- binding experiment consisting of dots moving in the same netic Tomography "LORETA") were computed.
or opposite direction presented at two identified regions in Comparing the two sessions, there was a significant corre- the visual field. The outlined multi-modal approach may lation between improved MMSE scores and more anterior provide a new research tool for non-invasively studying location of beta2 (r=0.69; p<0.05) and beta3 (r=0.78; p<0.05) the binding problem in the human brain and to learn about sources. Similar results were found computing gravity cen- the possibilities and limitations of high-resolution ters of the LORETA result volumes: beta2 (r=0.66; p<0.05) spatio-temporal fMRI/EEG/MEG mapping.
and beta3 (r=0.82; p<0.05). Voxel-by-voxel LORETA im-ages showed increased activation in the right middle/su- The Influence of Brain Anisotropy on Human EEG and
perior temporal gyrus for beta2 and beta3 with improved MEG. - J. Haueisen*, D. S. Tuch+, C. Ramon^ and P.
MMSE, i.e., in areas known to be impaired in DAT S c h i m p f ~ ( * B i o m a g n e t i c C e n t e r , F r i e d r i c h-
(Desgranges et al., 1998; deToledo-Morrell et al., 1997).
Schiller-University, Jena, Germany, +Massachusetts
General Hospital - NMR Center, Charlestown, MA,
A New Approach to Study Temporal Coding in Early
USA, ^Department of Electrical Engineering, Univer-
Visual Areas of the Human Brain. -R. Goebel (Dept. of
sity of Washington, Seattle, WA, USA, ~Department of
Neurocognition, Faculty of Psychology, Maastricht
Computer Science, Eastern Washington University,
University, Netherlands).
Cheney, WA, USA).
Cognitive functions such as perception, memory The electrical conductivity of brain tissue, particu- and language are based on massively parallel informa- larly white matter, is known to be anisotropic. However, tion processing involving many cortical and subcortical basically all currently used modeling approaches in brain areas. This raises the question of how this distrib- source localization neglect anisotropy.
uted information is (re-)integrated, and how features The influence of gray and white matter anisotropy from different entities (such as different visual objects) on the human EEG and MEG was examined with a high are kept apart. This problem is known as the "binding resolution finite element model of a human head. We problem". A proposed solution of the binding problem quantified this influence by comparing simulated EEG assumes that the exact timing of neuronal discharges and MEG maps using three different types of volume provides a temporal coding scheme. In this scheme dif- conductor models: a detailed inhomogeneous model ferent features of different entities can be separately asso- with anisotropic conductivity tensors, a detailed ciated through synchronous oscillatory discharges.
inhomogeneous model with isotropic conductivity val- There is accumulating electrophysiological evidence ues, and a three compartment model. The conductivity from animal research that binding is indeed reflected in tensor data for gray and white matter were obtained synchrounous oscillatory activity above 30 Hz (gamma from magnetic resonance diffusion tensor imaging.
band). Human studies using EEG or MEG have also re- Anisotropic volume conduction in the brain was cently shown that gamma band activity increases in spe- found to have a minor influence on the topology of EEG cific time windows after the presentation of coherent vs.
and MEG (and hence source localization) but a major in- incoherent visual stimuli. These studies, however, have fluence on the amplitude of EEG and MEG (and hence so far failed to localize and separate the underlying We propose a new approach to study synchronization Influence of Conventional and Newer Antidepressive
phenomena in the human brain in a manner very close to Drug Treatment on Cognitive Evoked Potentials in Pa-
the approach used in electrophysiological animal experi- tients with Depressive Disorder using LORETA. - W.
ments. This approach requires the integration of M. Herrmann and J. Gallinat (Laboratory of Clinical
high-resolution fMRI, high-density EEG/MEG recordings Psychophysiology, Department of Psychiatry,
and appropriate three-dimensional cortex reconstruction Benjamin Franklin Hospital, Free University of Berlin,
techniques. The main idea is to increase the spatio-temporal Berlin, Germany
resolution of EEG/MEG by exploiting the results of The results of a recent investigation using LORETA fMRI-based retionotopic mapping experiments. We first (Low Resolution Electric Tomography) are compared select surface patches in early visual areas on the folded cor- with classical Pharmaco-EEG results.
In the recent investigation, the N100 and P300 compo- studies elicited this face-specific ERP with the presenta- nent was recorded using the auditory "oddball" paradigm tion of smiling faces. As differences in amplitudes ac- in 25 drug-free monopolar depressive patients before and cording to the emotional valence of the stimuli were after 4 weeks of antidepressive monotherapy and 25 nor- found as early as 100 ms after stimulus presentation mal controls matched with respect to age and sex. Pretreat- (Pizzagalli et al., 1999), this ERP might also be affected by ment amplitudes of the N100 (Cz) and frontal P300 (Fz) in the emotional valence of the stimuli. In order to investi- depressive patients were smaller as compared to controls.
gate the effect of facial expressions, event related poten- N100 amplitude (Cz) was negatively correlated with the tials (ERPs) elicited with sad, happy and neutral faces Hamilton depression score (HAMD) and P300 amplitude were compared to those elicited with buildings in 16 (Pz) correlated negatively (trend) with the HAMD.
healthy subjects. ERP-analysis confirmed a face specific With classical evaluation of N100 and P300, no change P160 component at vertex. In contrast to our hypothesis of either component after 4 weeks of treatment with con- we did not find any differences in amplitudes between ventional or newer antidepressants was observed in con- sad, happy or neutral facial expressions in that time seg- trast to results reported by Gangadhar et al. (1993).
ment. The results indicate, that face perception seems to However, the N100 and P300 are a composition of be processed independently from the decoding of differ- multiple coactive generators. Interesting aspects can be demonstrated using LORETA to follow the course of ac-tion in each location separately.
Electrophysiological Cue-Reactivity in High and Low
Social Drinkers. - M.J. Herrmann, A.J. Wiesbeck, H.-G.
Right Hemispheric Shift for the Processing of Negative
Weijer, J. Böning and A.J. Fallgatter (Psychiatric
Facial Expressions. - M.J. Herrmann*, H. Ellgring+ and
Neurophysiology, Department of Psychiatry and Psy-
A.J. Fallgatter* (*Psychiatric Neurophysiology, Depart-
chotherapy, University Hospital of Wuerzburg, Ger-
ment of Psychiatry and Psychotherapy, University
Hospital of Wuerzburg, Germany , +Institute of Psy-
A cue-reactivity has been described for different chology, University of Wuerzburg).
physiological variables including electrophysiological The processing of facial expressions was investi- measures, like event-related potentials (Herrmann et al., gated using event-related potentials (ERP). Sad, happy in press) in alcohol-dependent patients. However, it can and neutral facial expressions were presented for 500 ms be observed that some healthy subjects display such an to 16 healthy, right-handed subjects. The ERPs elicited electrophysiological cue-reactivity as well. The aim of with the facial expressions were recorded from 21 leads, this study, therefore, was to assess the effect of drinking and both the amplitudes and the topography were calcu- behaviours of healthy subjects on the cue-reactivity as lated in time segments determined based on the Global measured with event-related potentials (ERPs).
Field Power. Neutral facial expressions elicited higher In 15 high and 15 low social male drinkers ERPs amplitudes as compared to happy and sad faces in an were registered with 21 scalp electrodes while 8 alco- early time segment lasting from 148.4 - 265.4 ms after hol-related and 8 neutral pictures were presented. Stim- stimulus presentation. A significant topographical effect uli were presented for 500 ms each with an interstimulus was found in a later time segment from 269.5-371.1 ms.
The centre of gravity of the positive brain electrical fields A stronger cue-reactivity consisting of significantly was located over right-hemispheric brain regions in all higher amplitudes in the ERPs elicited with alcohol-related three conditions, with the most right-hemispheric posi- as compared to unrelated pictures was found in high social tion for sad faces. These results indicate that different drinkers. This result indicates that the electrophysiological neuronal assemblies are involved in the processing of fa- cue reactivity previously found in alcohol-dependent cial expressions, depending on their emotional content.
drinkers also occurs in social drinkers and that this cue re-activity is associated with the alcohol drinking customs.
The Face-Specific Event-Related Potential (P160) is Not
Affected by the Facial Expression. - M.J. Herrmann*, H.
Electrophysiological Cue-Reactivity in Alco-
E l l g r i n g + a n d A . J . F a l l g a t t e r * ( * P s y c h i a t r i c
hol-Dependent Patients.- M.J. Herrmann, H.-G.
Neurophysiology, Department of Psychiatry and Psy-
Weijers, G.A. Wiesbeck, J. Böning, A.J. Fallgatter(Psy-
chotherapy, University Hospital of Wuerzburg, Ger-
chiatric Neurophysiology, Department of Psychiatry
many, +Institute of Psychology, University of
a n d P s y c h o t h e r a p y , U n i v e r s i t y H o s p i t a l o f
Wuerzburg).
Wuerzburg, Germany).
The face-specific event-related potential (ERP) oc- In alcohol-dependent patients a cue-reactivity can be curring 160 ms after stimulus presentation has been de- observed for subjective and physiological measures.
scribed by different research groups. However, most Conditioning models of alcohol addiction suggest that stimuli associated with previous drug use (cues) may ini- phy (LORETA) from spontaneous EEG, separately for tiate reward craving and relapse in a definite subgroup of patients. Event-related potentials (ERPs) might be useful The study was carried out on 12 patients with de- to reveal the brain functional substrates of cue-reactivity.
mentia. Nicotine was administered transdermally for 4 In 19 male alcohol-dependent patients (44.2 ± 8.5 years) weeks. The patients were examined before and 4 weeks and 19 male healthy controls (42.5 ± 12.5 years) after administration of nicotine. Eighteen electrodes EEG event-related-potentials were registered with 21 scalp during resting was recorded before and after administra- electrodes while 15 alcohol-related and 15 neutral words tion of nicotine. Three-dimensional images of cortical were presented. Significantly higher amplitudes in the electric neuronal activity, corresponding to the genera- ERPs after alcohol-related compared to unrelated words tors of different EEG frequency bands were computed by (cue-reactivity) was found in alcohol-dependent patients, but not in controls, at the electrode location Pz (F(1,36) = Significant effects were found, depending on brain 5.2, p < 0.05). The results support the concept that regions and EEG frequency band. The sources of EEG cue-reactivity in alcoholism is based on a neurobiological delta and theta activity attenuated at temporo-occipital substrate Future investigations will show whether this area after administration of nicotine. On the other hand, cue-reactivity can be applied for the evaluation of a the alpha 1 and 2 sources shift to more posterior locations cue-exposure therapy and the assessment of the risk of a resulted in nicotine administration. A significant de- relapse in individual alcohol-dependent patients.
crease in limbic lobe occurred in beta1-3 range.
A Visual-Semantic System Commonly Accessed by
Global Field Synchronization (GFS) in Cognitive Im-
Animals and Tools Categories as Revealed by
pairment.- D. Hubl*, T. Koenig*, V. Jelic+, L.O.
Event-Related Potentials.- J.A. Hinojosa*, M.
Wahlund+ and T. Dierks* (*University Hospital of
Martín-Loeches*+, F. Muñoz*, P. Casado*, C.
Clinical Psychiatry, Bern, Switzerland, +Alzheimer Re-
Fernández-Frías+ and M.A. Pozo* (*Brain Mapping
search Center, Department of Clinical Neuroscience,
Unit, Universidad Complutense, Madrid, Spain,
Karolinska Institute, Huddinge, Schweden).
+Dpto. de Psicobiología, Universidad Complutense,
Cortical functioning is necessarily associated with a Madrid, Spain).
well function neuronal network system. In the Two different approaches aim to explain the organiza- neurodegenerative course of Alzheimers dementia the net- tion of category-related knowledge in the semantic system.
work is deteriorated and the coherent work of neurons dis- One approach assumes a categorical organization in which rupted. Glucose metabolism (GluM) measured with PET is different categories are represented in segregated brain re- used as a diagnostic tool for Alzheimer dementia, and cor- gions. Another perspective postulates a non-categorical or- relates with the severity of the disease. This might make it ganization in which several categories place different difficult to differentiate in individual cases between pa- demands on shared brain subsystems. This study aims to tients and healthy persons. Similar is true for commonly investigate categorization processes by means of the Recog- used EEG parameters like Alpha- or Theta-Amplitude.
nition Potential (RP), an electrical brain response peaking at Global field synchronization (GFS) is presumed to measure around 250 ms that reflects semantic processing and is orig- the global coherence of electrical brain activity. Here we in- inated in areas subserving visual-semantic processing. Re- vestigated the influence of the disease severity on GFS and sults show that animals and tools categories similarly the relation between GFS and cerebral glucose metabolism.
access those areas generating the RP even though they were PET and GFS were accessed in 48 patients with Alzheimer supposed to differ in their processing demands. These find- dementia and 17 healthy controls. We could demonstrate ings are taken as supporting the non-categorical view, al- that the synchronisation in alpha band is significantly re- though introducing subtle variations since our data duced and allows thereby a differentiation between con- provide evidence of the existence of a brain subsystem spe- trols and AD patients similar to GluM results. However, in cialized in the processing of perceptual-semantic attributes contrast to GluM GFS did not correlate with severity of cog- that is equally accessed regardless of the semantic category.
nitive impairment. This may indicate, that global EEG syn-chronisation may become a more specific tool for A LORETA Evaluation of Nicotine’s Effects on EEG in
Alzheimer diagnostics compared to glucose PET.
Dementia.- K. Hirata, H. Tanaka, M Arai, M. Harada, T.
Suga, J. Kubo, T. Nagashima and K. Yamazaki (Depart-
Source and Conductivity Estimation in a Simultaneous
ment of Neurology, Dokkyo University School of Med-
MEG/EEG Analysis. - H.M. Huizenga, T.L. van Zuijen,
icine, Tochigi, Japan).
D.J. Heslenfeld and P.C.M. Molenaar (University of
We evaluate the efficacy of nicotine as a cognitive Amsterdam, Amsterdam The Netherlands).
enhancer with low-resolution electromagnetic tomogra- A method is described to jointly estimate source and conductivity parameters and the covariance matrix of cess. Second, the sources are estimated given this noise these parameters in a simultaneous MEG and EEG analy- model, which can be done very efficiently due to the sis. The method allows for unequal noise variances and nonzero noise covariances between sensors. This method Simulation results show that the source estimates has several advantages. First, it profits from the preferred are far more precise than those obtained from a standard directions of MEG and EEG, respectively transverse and analysis neglecting the noise covariance.
longitudinal. Second, it yields more precise estimates of An application to real EEG data shows that the deep sources than MEG alone. Third, the location of su- Kronecker description is valid, that the spatial covariance perficial sources profits from the tight MEG field, can be described by a simple distance dependent model, whereas the moment of superficial sources profits from and that the temporal covariance can be described by an EEG. Fourth, in contrast to MEG, radial moment can be autoregressive moving average model of limited order.
estimated, which also increases the precision of the otherparameters. And fifth, the conductivity parameters can Long-Term Memory Traces Facilitate Short-Term
be estimated. It is shown that conductivity estimation Memory Trace Formation. - M. Huotilainen, A. Kujala
improves precision greatly compared to using incorrect and R. Näätänen (Cognitive Brain Research Unit, De-
conductivity values. This is even the case if the data are partment of Psychology, University of Helsinki, Fin-
generated in a realistic head, and analyzed in concentric spheres. In that case conductivity estimation decreases Long-term memory traces of phoneme categories the location error from 1.74 to .32 cm, and the moment er- have an effect on short-term memory (Näätänen et al.
1997), as shown by the enhancement of the mismatchnegativity (MMN), an auditory event-related response to Optimal Sensor Positioning for Electromagnetic
a change in an ongoing sound stream, when the repeated Source Analysis. - H.M. Huizenga, D. J. Heslenfeld and
"standard" stimulus was replaced with a na- P. C.M. Molenaar (University of Amsterdam, Amster-
tive-language prototype phoneme compared to a dam The Netherlands).
non-prototype phoneme. The present study aimed at de- An analytic method is presented to compute optimal termining whether this facilitation affects the number of EEG/MEG sensor positions. The method consists of the stimulus repetitions needed to form an adequate mem- following stages. First, a source hypothesis is specified, ory trace used in change detection. We recorded MMNs this hypothesis can be derived for example from a pilot.
to infrequent stimuli occurring in trains of prototype and Second, the covariance matrix C of the hypothesized non-prototype phonemes, matched in their physical dis- source parameters is calculated. Third, the overall pa- tances to the standards, and in trains of sinusoidal tones.
rameter variance, as indexed by the determinant of C, is We found that the shortest trains of standards were minimized as a function of sensor positions. This yields needed to produce an MMN when native-language pro- totype phonemes were used as stimuli, suggesting that Simulation results and an application to a real EEG the automatic change-detection system can use informa- dataset indicate that the proposed method improves pre- tion from the long-term memory traces.
cision to a high extent. Source parameter standard errorshalved, and it became possible to separate two simulta- Source Localization of Brain Electric Activity During
neously active sources, which was not possible on a stan- Hypnotically Induced Anxiety and Relaxation. - T.
I s o t a n i * , H . T a n a k a + , D . L e h m a n n ^ , R . D .
Pascual-Marqui^, K. Kochi^, N. Saito*, T. Yagyu*, T.
Maximum Likelihood Spatiotemporal Source Analy-
K i n o s h i t a * a n d K . S a s a d a ~ ( * D e p a r t m e n t o f
sis. - H.M. Huizenga, L.W. Waldorp and R.P.P.
Neuropsychiatry, Kansai Medical University, Osaka,
Grasman (University of Amsterdam, Amsterdam The
Japan, +Department of Neurology, Dokkyo University
Netherlands).
School of Medicine, Tochigi, Japan, ^The KEY Insti-
tute for Brain-Mind Research, University Hospital of
spatiotemporal noise covariance in a source analysis. The PsychiatrY, Zurich, Switzerland, ~Nara Self-Control
essential feature is that the estimation problem is split Clinic and Institute of Psychology, Nara, Japan).
into two parts. First, a model is fitted to the observed The engagement of different brain regions which im- noise covariance matrix. This model is a Kronecker prod- plement subjectively experienced emotional states is not uct of a spatial and a temporal matrix. The spatial matrix clarified. We studied brain electric activity during hypnot- describes the spatial covariances by distance dependent ically induced anxiety and relaxation in eleven functions. The temporal matrix describes the temporal right-handed normals (26.5±7.6 years). After light hypno- covariances by an autoregressive moving average pro- sis, anxiety and then relaxation was suggested with a stan- dardized text. 19-channel, eyes-closed EEG (20 Subjects had to discriminate gratings of different seconds/subject) was analyzed using FFT approximation spatial frequency and orientation flashed sequentially and Low Resolution Electromagnetic Tomography and randomized in the left or right visual field. Task rele- (LORETA). Global tests revealed the strongest difference vant stimuli had an occurrence probability of 20%. The between EEG source gravity center locations during the EEG of 16 healthy adults with normal vision was re- two emotional states for excitatory beta2 frequency corded from 30 channels regularly placed between the (18.5-21 Hz). Post-hoc tests showed that the sources were located more right during anxiety than relaxation.
The main effects observed with relevant stimuli was LORETA specified that anxiety showed maximally stron- activation in the delta band and a reduction of the alpha ger activity than relaxation in right Brodmann area 10, and band over the contralateral occipital regions. For beta ac- relaxation than anxiety in left 22. Clearly, the two induced tivity (between 13 and 22 Hz) there was a different topo- emotional states were associated with different neural graphical pattern: it was significantly reduced over populations activity. Our results agree with reports on central and parietal areas for cortical processing of task brain activity shifted to the right (fronto-temporal) during negative compared with positive emotions.
Supported by Deutsche Forschungsgemeinschaft, Different Psychophysical Responses Correlated with
Topographical Differences During Binocular Rivalry
Mental Rotation of Alphabetic Characters and Human
of Faces. - A. Jedynak, E. Eger, T. Iwaki and W.
Hands: A High-Density Event-Related Potential Study.
Skrandies (Institute of Physiology, Justus-Liebig Uni-
- B.W. Johnson, Z.C. Thayer, J.P. Hamm, I.J. Kirk and
versity, Giessen, Germany).
M.C. Corballis (Department of Psychology, University
Does different perception of physically identical of Auckland, Auckland, New Zealand).
stimuli influence evoked potential topography in binoc- This study investigated brain processes concerned with the mental rotation of two classes of shapes: alpha- We presented schematic faces of brief duration syn- betic characters and human hands. 128-channel ERPs chronously in the left and right hemifield in a binocular were measured from 2 groups of normal, right-handed rivalry condition. In a forced-choice reaction time task, 31 human subjects. In both experiments, visual stimuli were healthy subjects decided which of two superimposed presented at varying angles from the upright orientation.
stimuli looked more „face-like". A regular array of 30 One group was required to decide if letters were normal channels recorded the EEG between the inon and 5% an- or mirror- reversed, while the other group was required terior of Fz. Analysis of the subjects’ responses revealed a to decide if hands were right or left hands. Late (latency "functional eye dominance" establishing three subject 300-800 ms) parietal negative waves were elicited in both groups (left, right, no eye dominance). Evoked potential tasks, and the amplitudes of these waves were data showed major components with mean latencies of monotonic functions of the angle of required rotation.
Other components in this time range had task-specific Subjects’ responses to shortly presented complex vi- spatial distributions. These data support the interpreta- sual stimuli enabled us to define an eye dominance dif- tion that the two rotation tasks engage some common ferent from conventional eye preference. Averaging brain mechanisms, particularly parietal cortex; and also according to stimulus as well as responses of the subject cortical mechanisms that are idiosyncratic to the mental allowed a detailed analysis of the evoked brain activity transformation of each class of shapes.
Supported by Royal Society of New Zealand Mar- Supported by Deutsche Forschungsgemeinschaft, Using Independent Component Analysis for Prepro-
Changes in Spectral Topography of Spontaneous EEG
cessing EEG/MEG Data. - J. Kastner, M. Fuchs and M.
During Lateralized Visual Attention Tasks. - A.
Wagner (Neuroscan Labs, Lutterothstr. 28e, 20255
Jedynak, T. Hayakawa and W. Skrandies (Institute of
Hamburg, Germany).
Physiology, Justus-Liebig University, Giessen, Ger-
For source reconstruction, an appropriate source model has to be chosen before solving the inverse prob- We analyzed topographical and global changes of lem. One common tool is the Singular Value Decomposi- spectral amplitude distributions induced by cortical pro- tion (SVD) of the measured data matrix, yielding not only cessing of visual information in healthy subjects per- the number of singular values above noise level but also forming a pattern discrimination task with lateralized the corresponding spatial patterns and time loadings. The main drawback of this approach is that the patterns and loadings are orthogonal to each other, and therefore not The high-frequency bursts occur with a significantly representing the true nature of the underlying activity.
longer latency in schizophrenic patients. The source Thus, an Independent Component Analysis (ICA) is power showed a tendency towards a higher amplitude in performed to reveal field patterns that are mutually inde- schizophrenics, while frequency remained unaffected.
pendent and not essentially orthogonal. The components The results will be discussed in the context of found by the algorithm are extracted from the mixing matrix and sorted by their relevance to the data.
The performance of the ICA is compared to SVD, us- Temporal Structure of Frequency-Tagged Coherent
ing simulated data with an analytical head model. Calcu- Multimodal Evoked Neuromagnetic Fields. - T.
lations are performed for strongly and weakly Kobayashi*, D. Cheyne+^ and T.Cheung^ (*Hokkaido
overlapping time loadings with gaussian noise added.
University, Sapporo, Japan, +Simon Fraser University,
Burnaby, Canada, ^CTF Systems Inc., Port Coquitlam,
Differences in Source Localiation of Electrical and
Canada).
Pressure Stimulated 96-Channel SEP. - W. Kawohl,
In an attempt to elucidate neocortical dynamics of T.D. Waberski, R. Gobbelé and H. Buchner (Depart-
conscious perception, we measured and analyzed ment of Neurology, RWTH Aachen, FRG).
neuromagnetic fields evoked by visual, auditory and We investigated the determination of the hand area somatosensory stimuli presented simultaneously. Each by dipole source estimation following artificial and natu- sensory stimulus was presented and tagged at a particu- ral stimuli. In principle there are advantages of both lar frequency. Four healthy male subjects participated in methods, pressure stimulation is less invasive, while the experiment. The neuromagnetic fields were recorded electrical stimulation can be applied with higher stimu- for 60 s in each trial using a 68-channel whole-cortex lus rates. Electrical and pressure-stimulation was per- formed simultaneously on the thumb and fifth finger of Coherent neuromagnetic fields over all sensor loca- six healthy volunteers. The SEPs following electrical tions were extracted as eigenvectors in single trial data stimulation show a sharper peak and a higher amplitude using principal component analysis after applying compared to the pressure-stimulated potentials. For both band-pass filters tuned for each tagged frequency. We stimulus qualities significant differences between the have devised a new method to retrieve temporal infor- source localization of the two fingers can be reported mation of the extracted eigenvectors by the projection of whereas the sources of the same finger following differ- original raw data to each eigenvector. It was found that ent stimuli show no significant difference concerning the time-frequency/scale structure of the retrieved tem- poral data could be clearly revealed by short time Fourier There is a tendency that, despite smaller source transform and continuous wavelet transform.
strenght, the spatial solution of the hand area is higheraccording to pressure-stimulation. This may be due to Global Field Synchronization (GFS), A New Way to
stimulation of more different receptor types by electrical F u n c t i o n a l
C o n n e c t i v i t y
stimuli represented in a larger cortical extension.
q u e n c y - D o m a i n
F i n d i n g s
Neuroleptic-Naïve Schizophrenics. - T. Koenig*+, D.
High Frequency Components of SEP in Schizophrenic
Lehmann+, N. Saito^, T. Kuginuki^, T. Kinoshita^ and
Patients. - W. Kawohl*, T.D. Waberski*, C. Norra+, R.
M. Koukkou* (*University Hospital of Clinical Psychi-
Gobbelé* and H. Buchner* (*Department of Neurol-
atry, Bern, Switzerland, +The KEY Institute for
ogy, RWTH Aachen, FRG, +Department of Psychiatry,
Brain-Mind Research, PUK, Zurich, Switzerland, ^De-
RWTH Aachen, FRG).
partment of Neuropsychiatry, Kansai Medical Univer-
Median nerve SEPs show an oscillatory burst of about sity, Osaka, Japan).
600 Hz superimposed on the N20 component (Gobbelé et In order to study global functional connectivity in al. 1998). This high-frequency component was supposed to frequency domain EEG, the measure of Global Field Syn- be generated in thalamo-cortical projection fibers (Gobbelé chronization (GFS) was developed. After the FFT, the et al. 1999). Alteration of the thalamic function which are method computes the principal components of the com- hypothesized in schizophrenia might be detectable by plex values over channels at a given frequency. The ratio analysis of the high-frequency part of SEP. We report dif- of the two eigenvalues indicates how much brain activity ferences between high frequency SEP of 12 schizophrenic was driven by a single phase. Higher ratios indicate more patients and age and gender matched controls. Median synchronization, thus higher functional connectivity, nerve SEP were recorded using 32 channels and evaluated lower values indicate decreased connectivity. The mea- by dipole source analysis and wavelet transformation be- sure is independent of the reference, contains no implicit fore and after application of a 450 Hz high-pass filter.
source models and avoids multiple testing.
In a first study of resting EEG of two independent data is composed of orthogonal elements, it does not as- groups of acute, first-break, neuroloeptic-naïve schizo- sume stationarity, topographical maps are obtained and phrenics compared to healthy controls, GFS values were it allows to include user defined, specific EEG elements found to be consistently reduced for theta activity like spike-wave patterns. The method will be introduced (6.5-8.0Hz). In the context of literature relating theta ac- formally and examples are given including artificial data tivity to memory functions, the result is interpreted as a and multichannel EEG during physiological and patho- functional disconnection of widespread neurocognitive processes subserving working memory functions inschizophrenia.
Do Wine Aromas Have Relaxation Effects? - Y. Koga, K.
Nakagawa, Y. Hirayasu, H. Nagai, Y. Nakamura, H.
Developmental Norms of Brain Electric Microstates. -
Tanahashi (Department of Neuropsychiatry, Kyorin
T. Koenig*+^, L. Prichep+, P. Valdes Sosa^, E. Braeker^,
University School of Medicine, Tokyo, Japan).
D. Lehmann~, R. Isenhart+ and E.R. John+ (*University
Effects of aromas on brain activity were evaluated by Hospital of Clinical Psychiatry, Bern, Switzerland,
using electroencephalography (EEG) in normal subjects.
+Brain Research Laboratories, NYU School of Medi-
EEG was measured for 3.5 minutes after exposure of each cine, New York, ^Cuban Neuroscience Center Ave. 25
aroma sample; 6 wines, ethanol solution, and distillated esq. 158, Playa, Havana, Cuba, ~The KEY Institute for
water (DW), with a 5 munites interval. Frequency power Brain-Mind Research, PUK, Zurich, Switzerland).
spectrum was analyzed on selected EEG waves for 30 sec- In EEG, time epochs with stable field topography can onds from each session. Relative power spectrum was be observed. These so-called brain electric microstates pre- calculated for 6 frequency bands from each sample rela- sumably correspond to a sustained coherent activity of ex- tive to those from DW at 12 electrode sites. Repeated mea- tensive functional networks. When EEG data is parsed into surement ANOVA (Sample and Electrodes as within distinctive microstates, one can classify and quantify differ- factors) was applied with the relative power on each fre- ent brain functional states mediated by such networks; the quency band. Significant main effect of sample was found time resolution is compatible with rapid information pro- in all frequency bands, except 11-12 Hz. Follow-up cessing. We established the age norms for basic microstate ANOVA suggested that odor from Chardonnay and parameters such as mean duration and frequency of occur- Concord significantly increased power for 9-10 and 10-11 rence using an EEG database of 496 subjects between 6 and Hz bands compared to ethanol solution. In addition etha- 80 years. We found that brain electric microstates evolve in nol solution did not change the power spectrum com- a discontinuous and non-linear way. Several putative brain developmental stages were observed, separated bychanges in microstate parameters. These stage changes oc- Source-Current Density in the Brain Underlying Ver-
curred at 12, 16 and 21 years of age. The result is discussed bal and Spatial Cognitive Activity. - Z.J. Koles and J.C.
in the framework of developmental psychology and state Lind (Department of Biomedical Engineering, Univer-
sity of Alberta, The Clinical Diagnostics and Research
Center, Alberta Hospital, Edmonton, Canada).
Topographic Time-Frequency Decomposition of the
The source-current density in the brain underlying 43 EEG. - T. Koenig*+, F. Marti-Lopez* and P.Valdes-Sosa*
channel EEGs recorded from 33 normal female subjects (*Cuban Neuroscience Center, POB 6880, La Habana,
while at rest and while engaged in the execution of verbal Cuba, +University Hospital of Clinical Psychiatry,
and spatial cognitive tasks was examined. Source-current Bern, Switzerland).
densities were computed using the LORETA algorithm at Topographic time-frequency decomposition is a 2394 locations in the gray matter of the brain and com- new computerized EEG analysis combining available pared in the theta and alpha frequency bands using multi- techniques from time-domain spatial EEG analysis and ple pair-wise t-tests. The Type I, or false-positive error rate, time-frequency decomposition of time series. A new, was controlled using a randomised hypothesis testing pro- physiologically and statistically plausible topographic cedure. Significant differences between the tasks and the time-frequency representation of multi-channel EEG is resting condition based on the full cross-spectral matrices obtained. The EEG is accounted by coefficients of a large obtained from each subject in each frequency band were set of user-defined EEG like time-series localized in time nonspecific. However, a factorization based on the simul- and frequency; which are optimized for maximal spatial taneous diagonalization of the two cross-spectral matrices smoothness and minimal norm. The coefficients are then produced current density patterns corresponding to the cluster-analyzed, yielding a small number of field con- two active tasks that were highly lateralized. In the theta figurations which vary in intensity as a function of time band, the patterns of current density were much more lo- and frequency. The method does not assume that the Harmonic Structure and Topography of EEG Driving
and mutual information theory created in late eighties Reaction to Intermittent Photic Stimulation in
and developed in nineties. It has already succeeded in Children and Adolescents. - V.V. Lazarev*, D.M.
separating eye movement artifacts from human scalp Simpson+, B.M. Schubsky* and L.C. de Azevedo*
EEG recording. Several characteristic sleep waves can be (*Inst. Fernandes Figueira, FIOCRUZ, Rio de Janeiro,
recorded during sleep EEG recording. They are used as Brazil, +Biomedical Engineering Program, Federal Uni-
stage determining factors of sleep staging. We appliedICA method to the sleep EEG for the sleep waves separa- versity of Rio de Janeiro).
tion. 18 channels scalp digital EEG data were converted In 15 normal subjects, the correlation (Pearson’s R) into 18 by n matrix which was used as a original data ma- between the frequency profiles (EEG amplitude spectra) trix X. Independent source matrix U was obtained by in- of the driving reaction to photic stimulation at 3-24 Hz, dependent component analysis method (U=W*X, where and harmonics, were calculated in 15 leads. Driving was W is an 18 by 18 matrix obtained by ICA). ICA was ap- found in 70-100% of cases in the occipital and in 30-80% in plied to the original EEG containing sleep waves. Among central areas, with strongest responses in the alpha, and a the 18 independent components, components containing second maximum in the theta band. Profiles for the second characteristic shape of sleep waves could be identified.
and third harmonics were highly correlated with those of Each independent component was reconstructed into the fundamental, when considering the corresponding original montage by the product of inverse matrix of W EEG frequencies. Peak frequencies in profiles were close and U. This result might demonstrate that characteristic to the individuals’ background alpha rhythm. The profile sleep waves could be separated from original EEG of un- amplitudes and their Rs with occipital profiles, decreased known mixed neural origins by the ICA method.
towards the frontal region, where the maxima in theta andalpha bands were similar. There was highinterhemispheric correlation between profiles. Patients EEG Gamma Frequency Brain Sources Differ Between
with migraine had higher reactivity in theta and beta Meditation-Induced, Altered States of Consciousness.
bands, reduced spatial consistency in peak frequencies, - D. Lehmann*, P.L. Faber*, P. Achermann+, D.
and decreased interhemispheric correlation of profiles.
Jeanmonod*, L.R.R. Gianotti* and D. Pizzagalli^ (*The
KEY Institute for Brain-Mind Research, University
Hospital of Psychiatry, CH-8029 Zurich, +Institute of
Auditory Event-Related Potentials (AERP) in the Par-
Pharmacology, University of Zurich, CH-8057 Zurich,
ents of Schizophrenics. - I. Lebedeva and V. Orlova
Switzerland, ^Affective Neuroscience Lab., Dept. of
(National Mental Health Research Center, Moscow,
Psychology, University of Wisconsin, Madison, WI
Russia).
53706, USA).
The group of middle-age parents of schizophrenics EEG gamma frequency implements consciousness; was subdivided by psychiatrist into groups of mentally meditation alters consciousness. We analyzed healthy (11 subjects, 5 men) and those with different per- 27-channel EEG from Lama Ole Nydahl during four sonality disorders (11,4). AERP in the standard oddball meditations (two minutes each), repeated once: "Buddha paradigm (target 2000 Hz, probability 0.2; non-target 1000 in front"; "100-syllables Mantra"; "Dissolution"; "Recon- Hz) were compared between these groups and stitution". LORETA tomography (Pascual-Marqui) com- age-matched group of 11 healthy subjects (5 men) without puted the intracortical three-dimensional distribution of psychiatric disorders in first and second degree relatives.
the gamma (35-44Hz) generators (2394 voxels). Results: Statistical analysis revealed significant intergroup differ- all comparisons between meditations showed statistical ences (p<0.02-0.05 in parietal zones) only for N100 in ERPs significance (voxel-by-voxel T-statistics with nonlinear to non-target stimuli with its decrease in the groups of par- correction for multiple testing). All 3 maximal activity ents. Unexpectedly, there were not significant differences differences between meditations were localized right in- for N200 and P300, although the latencies of P300 were ferior posterior for "visualizing" meditation #1; left cen- tended (p<0.06) to be prolonged in parents with personal- tral for "language" meditation #2; and right anterior ity disorders. The findings show the impairment in the in- superior for "dissolution" meditation #3. For "reconstitu- formation processing in the parents of schizophrenics tion" meditation #4, localization was left central superior similar to that found in patients with schizophrenia.
vs meditation #1 and right posterior inferior vs #2 and #3,conceivably because of linguistic as well as visual com- Independent Component Analysis (ICA) Can Separate
ponents. Thus, different mentally self-induced altered Sleep Waves. - I.K. Lee (Department of Neurology,
states of consciousness are associated with different lo- Inha University Medical College, Inchon, Korea).
calizations of maximal brain electric gamma activity.
Independent Component Analysis (ICA) is a blind Grant #670806 from Institut für Grenzgebiete der source separation method using unsupervised learning Coherence Changes in the Scalp EEG Corresponding to
EEG/MEG can help to understand the spatio-temporal Verbal and Spatial Cognitive Activity. - J.C. Lind and
distribution of brain activity during cognitive tasks.
Z.J. Koles (Clinical Diagnostics and Research Center,
Alberta Hospital Edmonton and the Department of
Magnetoencephalographic Studies of the Auditory
Biomedical Engineering, University of Alberta, Ed-
Pathway. - B. Lütkenhöner (Institute of Experimental
monton, Canada).
Audiology, University of Münster).
The differences in coherence patterns in 43 channel Animal experiments as well as invasive recordings EEGs recorded from 33 normal female subjects while en- in humans revealed a high complexity of the functional gaged in the execution of verbal and spatial cognitive organization of the auditory cortex. Compared to that, tasks was examined. Coherencies between all of the sites the common interpretation of the auditory evoked field (903 combinations) were compared in the theta and al- (AEF), based mainly on the peak structure of the re- pha bands using multiple pair-wise t-tests. The Type I, or corded data, appears to be overly simple. Detailed anal- false-positive error rate, was controlled using a random- yses of a variety of experiments revealed indeed a more ized hypothesis testing procedure. Significant differ- complex structure of the underlying sources. In general, ences between the tasks based on the full cross-spectral a high intraindividual consistency of the spatio-temporal matrices obtained from each subject in each frequency AEF pattern contrasted with a high interindividual vari- band were few (less than 6). However, a factorization ability, presumably reflecting the anatomical variability based on the simultaneous diagonalization of the two of the auditory cortex. Individual details are generally cross-spectral matrices elicited numerous (more than sacrificed when trying to identify features common to all 100) electrode pairs where the coherencies were signifi- investigated subjects. While such a procedure has the cantly different (p<0.05). The patterns of differences in advantage of resulting in handy conclusions, it entails the magnitudes of the coherencies were more lateralized the risk that statistically significant results are obtained in the alpha than in the theta band. Phase differences in for meaningless parameters. For this reason it is more the two tasks were as large as 30 degrees.
sensible to investigate single subjects with high precisionand to put the observed AEF down to the underlying cor- C o m b i n i n g F u n c t i o n a l B r a i n I m a g i n g a n d
tical (and subcortical) structures on an individual basis.
Electrophysiology in the Study of Higher Visual Func-
Spatial information obtained by functional magnetic res- tion. - D.E.J. Linden*, T. Dierks+, L. Muckli^, J. Waltz^,
onance imaging (fMRI) could help to achieve this chal- D. Prvulovic~, M. Scherg# and R. Goebel% (*Dept. of
lenging goal, but only if it can be ensured that basically Neurology, Johann Wolfgang Goethe-Universität,
the same events as observed in the AEF are studied.
Frankfurt, Germany, +University Hospital of Clinical
Psychiatry, Bern, Switzerland, ^Max Planck Institute
Ongoing EEG Activity During Explicit Learning of
for Brain Research, Frankfurt, Germany, ~Dept. of Psy-
Words and Faces. - M. Mölle*, L. Marshall*, H.L. Fehm+
chiatry, Johann Wolfgang Goethe-Universität, Frank-
and J. Born* (*Department of Neuroendocrinology,
G e r m a n y ,
N e u r o l o g y ,
+Department of Internal Medicine, Medical University
Ruprecht-Karls-Universität, Heidelberg, Germany,
of Lübeck, Lübeck, Germany).
%Dept. of Psychology, Maastricht University, Nether-
Activation in different oscillating neural systems during implicit and explicit learning of words and faces The investigation of the spatio-temporal dynamics of was investigated by measuring the ongoing EEG activity.
cognitive functions in humans requires the combination During implicit learning power in lower frequency bands of non-invasive functional imaging techniques at high (delta, theta) was higher and parietal alpha activity was spatial and temporal resolution. We performed parallel lower than during explicit learning. These differences fMRI and MEG experiments with visual motion stimuli, were attributed to increased visual scanning during im- which provided insights into the generators of the early plicit learning. Comparison of trials with efficient vs. poor visual evoked potentials, while a joint fMRI and EEG memory performance at later retrieval testing indicated study of visual and auditory oddball paradigms revealed that explicit encoding is associated with upper alpha an overlapping system for the generation of the late cog- desynchronization and theta synchronization. The com- nitive potentials (P 300) in both domains. Visual bined measure of theta synchronization and upper alpha short-term memory was investigated with fMRI and EEG desynchronization was selectively enhanced over left using a delayed matching-to-sample paradigm. FMRI fronto-temporal cortical regions during explicit learning showed a prominent delay activity in the prefrontal cor- of words and over right parietal regions during learning tex, with a corresponding increase in high frequency ac- of faces (p<0.001). This striking topographical dissociation tivity at the respective frontal sites revealed by EEG. We between materials for the combined measure of theta and propose that the parallel application of fMRI and upper alpha EEG activity indicates that the mode of ex- plicit learning essentially relies on a joint activation within the time course of the global field strength (GFP). Topo- two neuronal circuitries: the thalamo-cortical circuitry graphical analysis was computed with the descriptors of presumed to subserve search processes within long-term memory, and the hippocampo-cortical circuitry subserv- Two major ERP-components have been detected: ing the actual encoding into memory.
59-148 msec and 152-586 msec after stimulus presenta-tion. Latencies between faces and landmarks ERPs did A c t i v a t i o n
L a n d m a r k s
not dffer significantly. Neither there were amplitude’s LORETA-ERP-Study. - Th. J. Müller, A. Federspiel, T.
Dierks and W.K. Strik (University Hospital of Clinical
By contrast to studies in healthy controls, we did Psychiatry, Bern, Switzerland).
not find face-specific activation and amplitudes seemed fMRI-studies support the hypothesis of the existence to be higher. Rather, there were no differences between of specialized brain regions involved during face recogni- ERPs of the complex visual stimuli. These results may tion that are mostly found in the right fusiform area. The give evidence that disturbance of orientation or mis- aim of the present study was the investigation of the time judging of faces is due to dysfunction of complex object course of the brain electrical response to the presentation of complex visual stimuli based on LORETA-solutions. 25subjects (39.4±9.4 yrs.) saw pictures of faces or buildings.
Functional Differences in the Processing of Concrete
Components of 21-channel-ERPs were assessed on the and Abstract Words Differing in Their Degree of
basis of the time course of the global field strength. The lo- Imageability. - M. Martín-Loeches*+, J.A. Hinojosa*, F.
calization of the electrical sources in a normalized Muñoz*, P. Casado*, C. Fernández-Frías+ and M.A.
Talairach space was calculated. T-levels > 3.65 were set to P o z o * ( * B r a i n M a p p i n g U n i t , U n i v e r s i d a d
be significant at a 5%-level. Between 51-138 msec more Complutense, Madrid, Spain, +Dpto. de Psicobiología,
face-activation at the left fusiform gyrus (t=6.3) was ob- Universidad Complutense, Madrid, Spain).
tained. Between 139-178 msec significant activations due Whereas several investigators assume a unitary mo- to faces were found at right fusiform gyrus (t=6.9) and dality-independent semantic system, others consider that posterior gyrus cinguli (t=7.2). Further hyperactivation it is segregated into modality-specific regions. Previous due to face-stimuli was found in the time window be- research has investigated this question by using concrete tween 179-295 msec with the right fusiform gyrus being and abstract words. However, an important variable such significant at a t-level of 6.3 and the left at t=5.6.
as the degree of imageability of the stimuli was not con- LORETA-results give evidence that right fusiform gyrus sidered in these experiments. In this study we attempted face-activation, as found in several functional studies, is to elucidate how concrete and abstract words highly dif- attributed to a time window of 138-295 msec.
fering in imageability are processed as reflected by abrain electrical response, the Recognition Potential (RP), Loss of Face-Specific Activation in Acute Schizo-
that indexes semantic processing. Our results show that phrenic Epsiodes: an ERP-Study. - Th.J. Müller*, A.J.
those brain regions originating the RP became more acti- Fallgatter+, G. Berger^, A. Federspiel*, A. Heidrich+
vated for concrete (more imageable) words, although ab- P s y c h i a t r i c
stract materials activated these areas to a greater extent Neurophysiology, University Hospital of Clinical Psy-
than other non-meaningful stimuli. This indicates that at chiatry, Switzerland, +Dept. of Psychiatry, Clinical
least part of the semantic system is specialized in the pro- Neurophysiology, University of Würzburg, Germany,
cessing of concrete-imageable words, although there is ^MH-SKY Park Ville, Australia).
not a full functional segregation since these areas are also Detection and processing of visual stimuli (faces or importantly accessed by abstract words.
landmarks) is fundamental in getting along with envi-ronmental and social interactions. These interactions are Spatio-Temporal Correlation Between Brain Electrical
typically altered in patients with acute episodes of Activity and Cerebral Blood Flow in Brain Activation. -
schizophrenia. The aim of the present study was to ex- K. Nagata*, S. Matsuoka+ and K. Yaguchi^ (*Depart-
plore neurophysiological processing differences in com- ment of Neurology, Research Institute for Brain and
plex visual objects in this certain sample.
Blood Vessels, Akita Japan, +Showa Hospital,
14 patients (33.9±10.9 yrs., 6 male) with acute psy- Shimonoseki, Japan, ^Faculty of Education and Hu-
chotic disorder according DSM-IV (298.8, 12; 295.7, 2; man Studies, Akita University, Akita, Japan).
PANSS: 63.7±14.5) saw pictures of faces or buildings.
Topographic mapping of EEG and ERP carries accu- Event-related potentials (ERP) were recorded with 21 rate temporal resolution, although the spatial resolution channels according the International-10-20-System.
is limited even with multichannel recordings. Con- Components of the ERPs were assessed on the basis of versely, positron emission tomography (PET) enables a quantitative measure of hemodynamic and metabolic current distribution, remaining consistent with variables with a precise spatial resolution, but the tempo- electrophysiology. From a mathematical viewpoint, ral resolution is not better than 60-90 sec due to its theo- LORETA yields a spatial low-pass filtered version of cor- retical limitations. The combination of topographic EEG tical current density. If there are no high frequency peaks mapping and PET provides a useful neurophysiological in the spatial spectrum of the current density, then informations with good spatio-temporal resolution by LORETA has low localization error. Quantitative neuro- supplementing the shortcomings of each modality.
anatomical validation for LORETA is presented based on Simultaneous recording of ERP and PET was carried measurements with visual and auditory stimulation, and out in 12 young male volunteers during the continuous in a verbal fluency task experiment.
performance task (CPT) paradigms in which the subjectswere requested to discriminate pictures of famous per- The Effect of Selected Prestimulus Activity on the Au-
sons’ faces ["face"], simple geometric figures ["figure"], or ditory P300 Paradigm: Application to Schizoprenia. -
Japanese words consisting of two Hiragana characters G.W. Price (Wolston Park Hospital, Queensland Cen-
["word"]. By the intravenous bolus injection of the oxy- tre for Schizophrenia Research, Australia).
gen-15 labeled water, cerebral blood flow (CBF) was mea- Interactive recording (iERP) is a method that can be sured repeatedly and the results were analyzed by the used to investigate the effect of an EEG pattern on the Event three-dimensional statistical method. Based on Related Potential (ERP). It involves real time processing of 32-channel EEG data, ERPs were averaged and the results the background EEG, and the application of stimuli in re- based on the global field power were analyzed statisti- sponse to the recognition of a pre-determined pattern.
cally. When the CBF images for "face" were compared An auditory oddball paradigm was implemented with those for "figure" or "word", a significant focal in- with Interactive recording in order to study the effect of crease in CBF was seen in the parahippocampal gyri, this form of recording in a population with treatment re- fusiform gyri and lingual gyri in a right-side dominant fractory schizophrenia. The pattern used had previously fashion. On the ERP results, three major positive peaks been found to be associated with an increase in ERP sig- were detected at 112, 164 and 244 msec. The peak second nal to noise ratio in single sweeps. The iERP was com- major peak was seen in the parieto-occipital regions and pared with the standard ERP from a matched recording the subtraction of the peak amplitude showed a marked without pre stimulus EEG testing. The results from 24 laterality between the "face" and "word". As previously subjects showed that the P300 amplitude derived from suggested in the literature, the ERP peak activity at 164 interactive recording, was significantly greater than that msec may carry the functional process of facial recogni- from a standard recording. The amplitude from both re- tion and be closely related with the bilateral mesial tem- cordings was significantly less in the schizophrenia poral and basal occipital activation on PET images.
LORETA: Possibilities and Limitations. - R.D.
Selective Impairment of Parietal Cortex Activation in
Pascual-Marqui*, M. Esslen*, K. Kochi*, D. Hell+, D.
Alzheimer Patients Duirng Visuospatial Tasks - A
Lehmann*, K. Hirata^, H. Tanaka^, B. Saletu~ and P.
Functional Magnetic Resonance Imaging Study. - D.
Anderer~ (*The KEY Institute for Brain-Mind Re-
Prvulovic*, D. Hubl*~, A.T. Sack*, L. Frölich*, M.
search, University Hospital of Psychiatry, Zurich; Swit-
Jandl*, H. Lanfermann+, F.Zanella+, K. Maurer*, R.
zerland, +University Hospital of Psychiatry, Zurich;
Goebel#, T. Dierks*~, D.E.J. Linden*^ (*+^Departments
Switzerland, ^Department of Neurology, Dokkyo Uni-
of Psychiatry and Psychotherapy, Neuroradiology,
versity School of Medicine, Tochigi; Switzerland, ~De-
Neurology, University of Frankfurt, ~University Hos-
partment of Psychiatry, University of Vienna, Austria).
pital of Clinical Psychiatry, Bern, #Department of Psy-
Multichannel EEG measurements do not contain suf- chology, University of Maastricht).
ficient information for determining uniquely the 3D elec- Impairment of visuocognitive abilities is a common tric neuronal activity distribution. Therefore, infinitely phenomenon in Alzheimer’s disease (AD). A couple of many solutions exist for this inverse problem. Many par- neuropathological and functional imaging studies ticular solutions have been published, each one character- proved the crucial role of the posterior parietal cortex in ized by some assumptions. The sole basis of "low spatial processing and transformation of visual objects.
resolution electromagnetic tomography" (LORETA) is an The aim of the following study was to determine whether electrophysiological one: scalp EEG is due to the instanta- the activation of parietal regions during visuospatial neous occurrence of highly synchronized post-synaptic tasks is differentially impaired by the neuropathological potentials in clusters of cortical pyramidal neurons. It will processes of AD and could therefore serve as a new be shown that the mathematical implementation of "syn- non-invasive diagnostic marker. 14 AD patients and 14 chronization" in LORETA over-blurs the estimated 3D age matched controls were investigated with fMRI while performing an angle discrimination task. The AD pa- a decrease in alpha activity, a slowing of the delta/theta tients showed a poorer performance on the task and re- centroid as well as an acceleration of the alpha and beta vealed a significantly lower activation in the right centroid, reflecting a decrease in vigilance. Correlation superior parietal lobule compared to controls. These re- maps showed significant relationships between these sults correspond to neuropathological findings in AD, EEG measures and the Hamilton depression score demonstrating a differential damage of cortical areas of (HAMD): the worse the vigilance, the more pronounced the visual system. This study shows that fMRI may be a the depression. In the alpha-asymmetry index, de- useful tool for the diagnosis and monitoring of AD.
pressed patients showed less power over the right thanleft frontal lobe, whereas normal controls exhibited the New Insights into the Functional Relevance of Parietal
opposite. The frontal asymmetry index was significantly Cortex Activation for Visuospatial Functions: Com-
correlated with HAMD, which suggests a right frontal bined Evidence from fMRI and rTMS. - A.T. Sack*, D.
hyper- and left frontal hyperactivation in depression.
Hub*#, D. Prvulovic*, E. Formisano%, M. Jandl*, F.E.
Sedative antidepressants of the imipramine/ Zanella+, K. Maurer*, R. Goebel%, T. Dierks# and D.E.J.
amitriptyline type attenuated total power, decreased ab- Linden*^~ (*Depts. of Psychiatry, Div. of Clinical
solute delta/theta and specifically alpha power, in- Neurophysiology, Universität, Frankfurt, Germany,
creased relative delta/theta and decreased relative alpha +Neuroradiology, Universität, Frankfurt, Germany,
and to some extent also relative beta power and slowed ^Neurology, Universität, Frankfurt, Germany,
the total centroid. This is partly in contrast to ~Max-Planck-Institut für Hirnforschung, Frankfurt,
non-sedative antidepressants, which attenuated total Germany, #University Hospital of Clinical Psychiatry,
power and absolute delta/theta power, but increased ab- Bern, Switzerland, %Department for Psychology,
solute and specifically relative beta power, slowed the Universität Maastricht, The Nederlands).
delta/theta centroid and accelerated the alpha and beta We combined functional magnetic resonance imaging centroid, as well as the total centroid.
(fMRI) and repetitive transcranial magnetic stimulation Finally, identifying cortical target regions of (rTMS) to investigate the functional relevance of parietal pyschotropic drugs by low-resolution brain electromag- cortex activation during the performance of visuospatial netic tomography (LORETA), we recently described that - tasks. FMRI provides information about the correlation be- at pharmacodynamic tmax - 20 mg citalopram induced tween local transient changes in neuronal activation and the most pronounced changes in the beta-3 and beta-2 specific cognitive functions. Information on the functional bands, showing a bilateral increase, predominantly in the relevance of this activation was obtained by using rTMS to frontal (F) and temporal (T), but also parietal (P) and limbic induce temporary regional deactivations as an independ- (L) lobes and sublobularly (S), further an increase in beta-1 ent variable and investigate its effect on the performance of and alpha-2 over the right F and T, but also L lobes and S as specific cognitive functions as dependent variables within well as a delta augmentation in the left F, T and P lobes.
a controlled experimental design. We investigated cogni- The results of a predominantly right hemispheric in- tive tasks that were performed on the same visual material crease in alpha-2 and beta-1 activity after 20 mg citalopram but differed in the demand on visuospatial functions. For are in agreement with the post-mortem neurochemical the visuospatial tasks we found a selective enhancement of studies of Arato et al. (1991), implying a higher 5HT turn- fMRI signal in the superior parietal lobule (SPL) and a se- over in the right non-dominant "affective hemisphere" lective impairment of performance after rTMS to this re- than in the left "cognitive hemisphere", which had already gion. We could thus show that the parietal cortex is earlier been reported by Flor-Henry (1985).
functionally important for the execution of spatial judge-ments on visually presented material.
Functional Imaging Improves When EEG/MEG is
Combined with MRI/fMRI. - M. Scherg (Sektion
Neurophysiological Aspects of Depression and Anti-
Biomagnetismus, Dept. of Neurology, University Hos-
depressants: EEG Mapping and Tomography
pital of Heidelberg).
( L O R E T A ) . - B . S a l e t u * , P . A n d e r e r * , G . M .
EEG or MEG data rarely permit to localize the source Saletu-Zyhlarz*, R.D. Pascual-Marqui+ (*Department
activities of all active brain regions. Resolution can be im- of Psychiatry, University of Vienna, Austria, +The KEY
proved using anatomical and functional information from Institute for Brain-Mind Research, Zürich, Switzer-
MRI and fMRI. For any active brain region, a spatial filter can be established by a linear combination of the record- Recent EEG mapping studies demonstrated that ing channels. However, when the number of active areas major depression was characterized by a decrease in ab- increases, the spatial filter must be sharpened to separate solute power in all frequency bands, a tendency towards the activities of all areas. Functional-anatomical informa- an augmentation of relative delta/theta and beta power, tion helps to confine source space by seeding of dipole sources into active brain regions or by priori weighting representations of 3D objects were identical or mirror im- over space (MRT/fMRT) and time (EEG/MEG) to focus aged within a rotation. Brain electrical activity was re- corded from 64 scalp sites while a diffuse 13Hz flicker We recorded tactile somatosensory evoked fields superimposed over the visual fields elicited the SSVEP.
(SEF) separately from tactile and motion tasks in fMRI.
During the period of mental rotation, increasing angular Source activities of the contralateral primary and second- disparity was associated with increased SSVEP amplitude ary areas were separated by multiple dipole modeling but at parietal, left temporal and prefrontal sites. Increased not by cortical current mapping. fMRI-based weighting angular disparity was also associated with increased improved separation considerably. By combining MRI- SSVEP phase-lag at prefrontal and left temporal sites.
and fMRI data of a patient with epileptic myoclonus of the During mental rotation occipito-prefrontal and hand, the multiple source model of EEG and MEG demon- parieto-prefrontal SSVEP partial coherence increased strated propagation from somatosensory cortex to motor, with increasing angular disparity. Our data suggests that premotor and contralateral motor cortex. Thus, by com- the SSVEP may offer useful information on the functional bining functional images with high spatial (MRT/fMRT) relationship between various brain regions during the and temporal (EEG/MEG) resolution we gain more in- creation and manipulation of mental images.
sight where and when cortical processing occurs.
Effects of Temporal Gaps Between Successive Fixation
Various Clinical Applications of the Deviation Ration
Targets on Discrimination Performance and visually
Topography (DRT). - F. Shichijo*, Y. Kaji+, M.
Evoked Brain Activity. - W. Skrandies* and E.
Akutagawa^, O. Takimoto*, S. Nagahiro*, H.
Anagnostou+ (*Institute of Physiology, Justus-Liebig
Nakayama~, Q. Zhang~ and Y. Kinouchi~ (*Department
University, Giessen, +Department of Neurology, Lud-
o f N e u r o l o g i c a l S u r g e r y , T h e U n i v e r s i t y o f
wig Maximilians University, Munich).
Tokushima,
+Faculty of Engineering, Tokushima
We studied how a specific oculomotor task influ- Bunri University, ^School of Medical Sciences, the
ences afferent visual processing. Twenty subjects had to University of Tokushima, ~Faculty of Engineering, the
perform visually guided saccades, and between the off- University of Tokushima, Tokushima, Japan).
set of the fixation light and the onset of the new target The deviation ratio topography (DRT) is our original there was a either a 200 ms temporal gap or no gap. Dur- software devised in 1986 to detect the dynamic EEG varia- ing saccades visual stimuli with different orientations tions. With DRT, not only the changes in frequency bands were presented, and discrimination performance and but also the spatial and sequential changes of EEG activi- topographic VEP activity was analyzed.
ties are visually evaluated statistically. The idea of DRT In the gap condition, more correct responses oc- was devised under the EEG constancy that the individual curred. However, global field power, evoked component EEG topography patterns show almost the same patterns latency and topography of the VEP were not affected by in the same condition. The DRT mapping is made of the the gap. This suggests that parieto-occipital areas need logarithmic ratio between the control data (C) and mea- not be the most important sites of sensorimotor integra- sured data (M) that is recorded on the same electrode un- tion. From perceptual data it is clear that intrasaccadic vi- der the different conditions. The formula is as follows: sual processing is influenced by presaccadic events.
logarithmic deviation ratio = log (M/C). The clinical appli- Under the short time constraints prevalent in the cations of the DRT were as follows: (1) the intraoperative saccadic task, fixation target cues are not only used for monitoring, (2) the EEG monitoring during the physiologi- motor planning, but also determine the visibility of vi- cal or mental tasks, and (3) the evaluation of EEG changes sual patterns presented during the eye movement.
after medication or operations. The DRT system for Win- Supported by Deutsche Forschungsgemeinschaft, dows has been developed in our institutes.
Changes in Steady State Visually Evoked Potential
The Influence of Visual Field Location and Frequency
(SSVEP) Amplitude, Phase and Coherence During
on Visual Perception and Brain Activity Elicited by
Mental Rotation. - R.B. Silberstein, F.M. Danieli and
Motion-in-Depth Stimuli. - W. Skrandies, A. Jedynak
P.L. Nunez (Brain Sciences Institute, Swinburne Uni-
and Ch. Kirr (Institute of Physiology, Justus-Liebig
versity of Technology. Melbourne, Australia).
University, 35392 Giessen, Germany).
In this study, we used scalp SSVEP amplitude topog- We investigated the effect of visual field location and raphy, SSVEP phase topography, and SSVEP coherence to motion frequency on psychophysical thresholds and brain investigate the organization of brain activity during the activity elicited by dynamic random-dot stereograms.
Shepard & Metzler (1971) mental rotation task.
Stereoscopic checkerboards were presented at ran- Twenty-two right-handed males indicated whether two dom centrally, or in the left or right visual field with hori- zontal disparity changing between 2 and 16 Hz. Ten gions EEGs of Alzheimer patients and controls with age subjects had to indicate whether and where stimuli had associated memory impairment were analyzed with lin- moved in depth. Simultaneously, electrical activity was ear and nonlinear measures of functional connectivity.
recorded from 30 electrodes over the occipital and parietal EEGs were recorded in 10 subjects (age 73.6 (SD 6.7); 5 brain areas. Steady-state VEPs were quantified by FFT.
males; 5 females) with age associated memory impair- Largest sensitivity occurred with central stimuli ment (AAMI) and 28 patients (age 73.7 (SD 6.6); 14 males; (mean 4.5 Hz) while laterally motion-in-depth could not 14 females) with Alzheimer’s disease all referred to an be perceived at frequencies exceeding 2.5 Hz. There was outpatient clinic for memory disorders. EEGs were ana- no difference between the left and right visual field.

Source: http://www.cannamuse.de/PDF/ISBET_PROCEEDINGS.pdf