446 Impaired visual processing in schizophrenic subtypes

Abstracts

/International

Journal

M. Weisbrod *l , M . Kiefer’, F. Marzinzik’, M. Scherg’, M. Spitzer 2 ‘University of Heidelberg, Department of Psychiatry, VossStrasse 4, Heidelberg, D-69115, Germany %niversity of Ulm The control of action and thought plays an important role in the organization of human behavior. Theories of attention have postulated an “executive control system” engaged in situations requiring decision making, conflict resolution, error correction, and response inhibition. Some schizophrenic symptoms can be conceptualized as failure of the “executive control system”. This system can be examined using go/no go tasks which require inhibition of a prepared response. In our study event related potentials (ERPs) were recorded while 16 healthy controls and 16 schizophrenic patients performed two different auditory go/no go tasks. In healthy controls two ERP effects were shown to be specifically associated with response inhibition: 1) A bilateral inferior frontal effect in the time window of the N2 ERP component. 2) An augmented fronto-central positivity in the time window of the P3 which was most prominent over left fronto-central electrode sites irrespective of the side of motor response. Source analyses suggested generators in the inferior prefrontal cortices to underly the effect in the N2 window, and sources near the frontal midline (approximately anterior cingulate cortex) and in the left premotor or motor cortex to underly the effect in the P3 window. In respect to the effect in the N2 window schizophrenic patients were not different from healthy controls. In contrast, the effect in the P3 window was significantly different between schizophrenic patients and controls. This finding points to dysfunctions in the anterior cingulate as the neuronal substrat of disturbed executive functions in schizophrenia.

445 ELECTROPHYSIOLOGICAL CORRELATES IMPAIRED A’ITENTION IN SCHIZOPHRENIA A. Basidska* Department of Psychiatry, Medical University Nowowiejska 27, Warsaw, 00-665, Poland

OF

of Warsaw,

50 male schizophrenic patients and 50 male age-matched volunteers performed the Continuous Attention Task (CAT). Target was defined as direct repetition of the same geometrical pattern. Visual potentials (VEP) evoked by CAT items were compared between the two groups and the differences were compared with CAT results. CAT revealed in patients signticantly higher index of errors (contributed by numerous omissions, while commission indices in both groups were comparable); lower detection index and longer reaction time, as compared to the control subjects. VEP examination re-

of Psychophysiology

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30 (I 998) 95-271

vealed in patients 1) lower non-target amplitudes of components Pl, Nl and P3a; 2) change during detection of target, i.e. an increase of amplitudes of occipital and posterotemporal Nl as well as of frontal P3a, while in the control group no significant changes of amplitude of that components occurred 3) delayed target P2, N2 and P3a latencies 4) lower amplitude of target P3b. Atypical increase of Nl amplitude, as well as delayed P2, N2 and P3a latencies and lower amplitude of non-target P3a, correlated with indices of omissions and errors. However, an increase of P3a correlated with relatively shorter reaction time. Those results confirm earlier data related to smaller sample and imply an occurrence of either pathological or compensatory mechanisms on higher level of processing in face of primary disturbances on lower, automatic stage.

446 IMPAIRED SCHIZOPHRENIC

VISUAL SUBTYPES

PROCESSING

IN

B. Van Sweden’*, F. Mesotten2, L. Crevits3 ‘Dept. Clin. Neurophysiol, ‘Dept. Psychiatry, Medical Centre St.-Jozef, Bilzen, B-3740 Belgium, 3Dept. Clin. Neurophysiol University Hospital Ghent, Belgium Topographic differences in flash (FEP) and pattern reversal (PREP) data are compared in paranoid (n = 381, disorganised (n = 23) and residual (n = 23) schizophrenia. The P, generated over the occipito-temporal regions reflects the ventral information stream encompassing feature analysis and object recognition. Pattern identification is well preserved in paranoid and residual schizophrenia. The dorsal visual information stream in contrast involves spatial perception and visuomotor functions and is reflected in the N,,, generated over the occipito-parietal cortex. This response is intact in paranoid, but diminished and delayed in residual and disorganised schizophrenics. Normal FEP/PREP data concur with a well preserved global personality functioning in paranoid schizophrenia. Latency increase and amplitude decrease of the pattern Nu, concur with abnormal antisaccades documented in disorganised behaviour.

447 EYE TRACKING SCHIZOPHRENIA DURING PURSUIT MOVEMENTS

ABNORMALITIES IN FIXATION AND SMOOTH

J.K. Rybakowskit* , A. Borkowska2 ‘Department of Adult Psychiatry, University of Medical Sciences, Szpitalna 27/33 Str, Poznan, 60-572 Poland 2Department of Psychiatry, Medical Academy, Bydgoszcz, POland Purpose of study. Eye tracking abnormalities have been considered as neurophysiological markers of schizophrenia. A pathology of left cerebral hemisphere in this illness has been