POSTER: SENSORY SYSTEMS Prefrontal Dysfunction in Neuroleptic-Naive Schizophrenic Patients D. F. Draus, G. Ende, W. Weber-Fahr, S. Stuck, A. Krier, F. A. Henn NMR Research in Psychiatry, Central Institute of Mental Health, Mannheim, Germany Introduction The frontal lobes in man with its phylogenctically youngest prefrontal cortex include about one third of the total cortical area of the cerebrum. a considerably greater proportion than in all other primates. It is likely that the frontal lobes play a prominent role in regulating and monitoring ..executive" cognitive processes. TItus. the prefrontal cortex occupies a pivotal point in many current theories of neuropsychiatric disorders. Strongevidence for prefrontal lobe dysfunction in schizophrenia comes from neuropsychological and electrophysiological paradigms as well as PET studies. Purpose The purpose of this study was to answer the question: Are disturbedfrontal networks in medication-naive patients with first-episode schizophrenia (leD 10. F20) detectable withfMRI during simple sensory stimulation? Materials and Methods We investigated 15 medication-naive. first episode schizophrenic patients (ICD lO-diagnosis F20.0. mean age 27 +/- 8 years. 8 f, 7 01) with a simple tMRI input paradigm and compared the results with 15age- and sex- matched controls. fMRI scans were acquired on a commercial Siemens Vision 1.5 T scanner using a multislice 20 EPI sequence with 19axial slices(3 rum thickness. I rum gap,64 • 64 matrix. 220 • 220 FOV, TE = 66 ms, standard space corresponding to the atlas of Talairach and Tourneoux (1988). As input we usedour well established simple visual (6 Hz checkerboard) and auditory (drum noise) stimulation paradigm applied simultaneously to the right- handed patients and matched controls. It was investigated in one block of 100 measurements alternating rest and activation in 5 groupsof 10 circles each. Preprocessing and data analysis was performed using custom software tools (3,4). In additionto realignment, spatial and temporal gaussian smoothing. removal of linear trend as well as nearest neighbour clusteranalysis havebeen performed. According to Bandettini activated pixels were identified by correlatingraw data with a convoluted reference function on a pixel by pixel basis (CC>0.45) (2.3). TIle major resultshave been cross-validated with SPM96 (4). Results WillI fMRI there were no differences in the activation pattern of the predefined sensory cortices (1'/-175. A 1-..12) but a significant (paired t-Test, ANOVA: p<0.05) prefrontal hypofunction in first-episode schizophrenic patients in comparison to controls. Conclusion Neuropsychological studies of brain function suggest that Ilte clinical phenomenology of schizophrenia may arise from abnormal neuronal connectivity in networks for "executive functions". Using fMRI and comparing medication-naive. first episode schizophrenic patients with matched controls. we found a different activation pattern in the prefrontal cortexbut no differences in visual and acoustic cortices (VI-V5, AI-A2). Our results are in line with PET studies and support the hypothesis that there is a disturbance in the prefronto-temporolimbic pathway in schizophrenic patients (I). Since attentional impairments have been found both in schizophrenic patients and in first-degree relatives of schizophrenic individuals (5). our results suggest that fMRI detects an abnormal attentional network in this condition and raises the possibility that one can non-invasively monitor a biological indicatorof liability to schizophrenia in populations at risk. References I. Weinberger. D.R.• Lipska B.K.Schizophr Res. 1995. 16: 87. 2. Bandettini, P.A.. et. at., Magn. Reson. Med.• 1993,30: 16\. 3. Goebel R. Neurolmage, 1996.3: 604. 4. Friston, KJ, et aI., HumanBrain Mapping. 199-t.1: 153. 5. Reitman S.E.L. et aI, Am. J. Psych .. 1997. 154: 655. 5389