Synthesis of MEG and MRI

Abstracts / Psychiatry Research: Neuroimaging 68 (1997) 155-184 anxiolytics of the benzodiazepine type. Beyond the classification pharmaco-electroencephalography has become increasingly important in determining whether the drugs, especially non-CNS drugs, do have pharmaco-dynamic effects on the brain function. Pharmaco-EEG also has been well established for determining whether the kinetics of the pharmaco-dynamic effects on brain function are different from classical plasma kinetics. There are sufficient examples for clockwise and anti-clockwise historesis if plasma levels and effects on the CNS are compared. In the background, taking into account the well established specific effects of psychotopic drugs on the EEG, several attempts have been made to classify psychiatric disorders based on the EEG alone, The question, whether depressive disorder has typical EEG deviations, which can be discriminated from schizophrenic and normal patterns, has been controversially discussed. Our own findings confirm those of R. John and his associates, which show that retrospective and prospective classification is possible, if a certain fuzziness is allowed. Furthermore our results indicate that the disease-specific changes are stronger than the drug-related EEG changes, which givcs us the hope that disease-specific elements in the EEG can be discovered even under drug treatment. Motor activation in catatonic schizophrenics using FDG-PET A, Hcrtel ~, G, Northoff b, S. Sengupta u, D. Khoram-Sefat:', J. Eckert h, R.P. Baum a, B. Pflug h, G. H6r a

aDepartments of Nuclear Medicine, 6Psychiatry 11 and CNeuroRadiology, Goethe Unit,ersity Medical Center, Frankfurt, Germarly.

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Positron emission tomography (PET) studies in patients with Alzheimer dementia are sensitive in identifying even early stages. Evaluation of all diagnostic methods might be necessary for decisive diagnosis. Recently, the cholinesterase inhibitor tacrine has been used with success in Alzheimer patients. We used PET investigations to evaluate Alzheimer patients before and after therapy with tacrine. Eleven patients fulfilled criteria for Alzheimer disease (MMSE, ADAS or GDS clinical tests) and demonstrated in PET typical glucose metabolic cortical defects. All patients received tacrine. Mean age at PET investigation was 69.4, five males and six females. Mean MMSE score was 18.1, mean ADAS score (cognitive only) 18.1 and mean GDS performance 3.7. PET studies were performed on a Siemens ECAT 47 PET tomograph. F-18 Deoxy-glucosc (FDG) was injected i.v. and scans performed 30 rain post-injection for 30 rain. Nine out of eleven patients demonstrated typical cortical glucose metabolic deficits: temporo-parietal a n d / o r frontal. One patient had a unilateral temporo-parietal deficit, and two patients had subtle deficits but fulfilled clinical criteria. In four patients follow-up PET scans after a period of tacrine medication (80 rag/daily, interval between scans 8 and 30 months, mean 14 months) were available. The PET scans resulted in different findings: 2 patients showed worsening of PET findings, one with clinical deterioration and the othcr not; one patient was unchanged, and onc patient improved slightly. Though our figures are too small for gcneral conclusions, they nevertheless reveal interesting data for follow-up of Alzheimer patients under taerine medication. It seems that patients react differently under tacrine and that PET might bc of importance in defining different subgroups of patients. The effect of photic stimulation for the spatial EEG structure T. Hirota ", T. Kinoshita ~. T. Yagyu `''h, N. Saito a, M. Saito:'

Schizophrenic patients may exhibit reduced cerebral glucosc metabolic rates under activation testing. In catatonic patients the motor cortex is of special interest because of its involvement in this form of schizophrenia. Cerebral glucose metabolism was investigated using positron emission tomography (PET) under motor activation testing. Five catatonic patients were studied using PET scanning after i.v. injection of F-18 Deoxy-Glucose (FDG) and 4 days to 5 weeks after acute catatonic episodes. Medication was not discontinued. All gave informed consent for the investigation. Before and during injection until 10 min after injection, patients continuously performed finger sequencing as a motor activation task. Cerebral glucose uptake was measured in the motor cortex and supplementary motor area; comparison with contralateral areas to the dominant hemisphere was performed and correlated intrandividually. We report our first results in catatonic schizophrenics performing a motor activation task. PET investigations of AIzheimer patients before and after therapy with tacrine cholinesterase inhibitor A. Hcrtel a, L. Fr61ich b, S. Sengupta ~. J. Eckert h, R.P. Baum ~, K. Maurer b, G. H6r ~' a

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Department of Nuclear Medtclne and Department o~ Psychta ~' I. Goethe University Medical Center, Frankfurt / Germany.

~'Department of Neuropsychiatr); Kansai Medical Unit,er~ity, Osaka, Japan. hDepartment of Psychiato', Unit,er~itvHo.spitalZiirich, Switzerland EEG changes induced by photic stimulation havc been studied and reported. However, those studies mainly focuscd on the alpha frequency band. Although its cerebral dominance has been carefully evaluated, unfortunately not much attention has been paid to the phasc differences among leads. In this report, the spatial EEG structure of 14 young healthy males (right handed) during eyes closed photic stimulation (3, 5, 7, 9, 11, 13, 15 and 25Hz) was studied by using the FFT dipole approximation method which makes it possible to estimate the phase differences among multiple leads. Dipole locations of higher harmonics of the photic stimulation frequency shifted to posterior. Of all the possible directions the dipole could be moved, only two tendencies were observed, rcgardless of the stimulation frequency. These wcrc posteriol, left, up and anterior, right, down. Synthesis of MEG and MRI M. Hoke, B. Liitkenh6ner

blstitute of Fxperimental Audiology. Unit.,er~ityOf Miinstel. (ierlrlanv

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Abstracts / Psychiatry Research: Neuroimaging 68 (1997) 155-184

Both EEG and MEG can be considered as time-varying spatial patterns, sampled at a limited number of discrete locations. Using an appropriate interpolation, these patterns can be visualized, separately for each time point, as maps showing how the electrical potentials or the measured field components are distributed over the measurement surface. There is no doubt that different maps indicate that different generators are activated within the brain. However, the characterization of a brain state in terms of the activated sources represents a serious problem. Most studies up to now are based on discrete dipole models, especially single dipole models and multidipole models with simultaneous activation or not-simultaneous activation. However, results obtained with such models should be considered with care, especially if the number of channels is relatively small. The difficulties resulting from the non-uniqueness of the inverse problem are truly severe. However, a much different situation arises if the information content of EEG and MEG is considered in the context of other sources of information which are known a priori. A natural first step is the reduction of the source space. This can be done by assuming that the sources are located on the cortical surface, with an orientation perpendicular to the surface. Information about the cortical surface can easily be obtained by magnetic resonance imaging (MRI). The model of a single current dipole was replaced for that purpose by a dipole patch model. The idea underlying this model is that the source of the magnetic field corresponds to a uniformly activated patch of the cortical surface. Both the current dipole model and the dipole patch model were applied to somatosensory evoked fields (SEF). First results suggest that the dipole patch model is highly superior to the usual current dipole model, especially if a realistic volume conductor model is used rather than the present standard, the simple model of a homogeneous sphere. Cortical connections imaging A.M. Ivanitsky

Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia To know not only 'where' but 'how' information is processed in the brain one needs to have the picture of cortical areas interaction, not available with the most brain imaging methods. Approaching the problem the method was elaborated, based on the idea that cortical connections were promoted with the neuronal oscillators synchronization, revealing particularly in the precise coincidence of the EEG and ERP spectral components in the interacting cortical areas. The method was applied for the study of the brain mechanisms in thinking operations. The main result was that the cortical connections at mental task solving converged to the particular cortical zones typical for e.g. abstract vs. imaginative thinking. These cortical areas were named the interaction foci. We hypothesize that these connections centers realize the function of the comparison and the synthesis of information coming to the focus resulting in decision making. The method was applied also to the mental pathology study.

Application of artificial neural networks to CNV data to investigate schizophrenia B.W. Jervis a. M.R. Saatchi a, S. Yu a, R.F. Harrison b, C.P. Lim b, S. Oke c

aSchool of Engineering, Sheffield Hallam University, UK. bDepartment of Automatic Control and Systems Engineering, University of Sheffield, UK. CTon Vale Hospital, Taunton, UK The results and usefulness of applying data extracted from the Contingent Negative Variation (CNV) response in the electroencephalogram (EEG) of schizophrenic patients and their age and sex matched normal control subjects to artificial neural networks in o r d e r to differentiate between schizophrenics and normals are presented. Schizophrenia is a condition associated with psychiatric symptoms including hallucinations, delusions, and thought disorder. MRI and neuropathological studies have shown that there are functional and anatomical defects in the brains of schizophrenics, and the CNVs of schizophrenics have been found to be altered. The CNVs of 20 schizophrenics, the severity of whose symptoms had been assessed, and their matched normal controls were recorded using vertex and pre-frontal electrodes. After pre-processing, features were extracted from the data preceding the imperative stimulus. The normalized features were used to train multilayer perceptrons (MLPs) and a fuzzy ARTMAP to differentiate between the schizophrenics and their controls. The results were assessed in terms of the standard medical statistics of sensitivity and specificity etc.. The vertex electrode was found to be the more accurate marker for schizophrenia. Because of the possible overlap of symptoms in the early stages between schizophrenia and Huntington's disease (HI)), it was established that the neural networks could be trained to distinguish between thc CNVs of schizophrenic and HD patients. Establishing the architectures and training MLPs is very time consuming. Good results were much more quickly obtained using the fuzzy ARTMAP which also solves the plasticity-stability problem. Another advantage of the fuzzy A R T M A P is that examples which do not belong to any known category may be assigned to a new cluster and be associated with an 'unknown' class. The difficulty of assessing the reliability of a classification by neural networks may pose a problem. However, this can be solved using a statistical analysis method such as predictive statistical diagnosis, which yields probabilities and atypicality indices provided the data are rendered normal, or principal components analysis. MRI-guided SPECT-measurements of medial temporal lobe blood flow in Alzheimer's disease P. Julin '~, L. Svensson b, O. Almkvist", K. Mfi.hrc ~:, LO. Wahlund ;~

aDepartment of Clinical Neuroscience, Geriatric Section, Karolinska Institute, Huddinge Univers'ity Ho.spital, Stockhohn, Sweden. Ho.wttal Phystcs, Karolinska Institute, Huddinge University Hospital Stockhohn, Sweden. CDiagnostic Radiology, Karolinska Institute, Haddhlge Univers'itv Hospital, Stockhohn, Sweden b

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MRI-guided hippocampal/cerebellar CBF-ratios werc mcasurcd on images from eight healthy controls and one subjcc!