363. TEST-RETEST RELIABILITY OF BRAIN SPECT STUDIES IN NORMALS L.M. Konopka, S.L. Nahas, A. Dekhtyar, B.D. Twardowska, E. Massey, T.B. Dobrzynski, P. Shirazi, J.W. Crayton Hines VA Hospital, Hines, Illinois 60141 Brain HMAO SPECT studies are used to evaluate brain activity in clinical populations. SPECT studies are also conducted in protocols comparing the brain’s resting state with that seen during an activation procedure. However, no data are available to evaluate the stability of these measures over time. We conducted HMPAO-SPECT studies of 6 normal control subjects (3 males age 32 6 6.5 years and 3 females age 31 6 14.5 years) on two occasions at least one week apart. Conditions of each study were maintained constant. To minimize the effects of ambient sound and light, subjects were injected while reclining in a relaxed mode in a sound-attenuating booth with eyes covered. To reduce anxiety, the HMPAO was injected via a previ- ously-prepared I.V. line which passed out of the booth. The SPECT images were obtained by triple-headed gamma camera one-hour post-injection of the standard dose of 25 mCi of Tc-99m HMPAO. The analysis of images involved coregistration in space and intensity normalization. Two methods of analysis were used. One, involved the analysis of regions of interest identified by MRI. Method two involved voxel-by-voxel evaluation based on Statistical Parametric Mapping (SPM). The results of these analyses showed that there were no significant differences between the two studies. The range of differences in the ROI analysis was 1–2.5%. The SPM analysis resulted in no detectable difference at the level of p , 0.05. These data provide evidence that brain perfusion studies by HMPAO SPECT under well-controlled conditions are a stable and useful tool for the evaluation of brain function over time. 364. REPRODUCIBILITY OF WATER ACQUIRED 1 H-MRSI DATA IN HEALTHY SUBJECTS A. Bertolino, J.H. Callicott, V.S. Mattay, J.W. van der Veen, J.H. Duyn, R. Rakow, K.M. Weidenhammer, D.R. Weinberger Clinical Brain Disorders Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892 USA Proton magnetic resonance spectroscopic imaging ( 1 H-MRSI) maps brain chemicals including N-acetylaspartate (NAA, a marker of neuronal integri- ty), choline-containing compounds (CHO), and creatine 1 phospocreatine (CRE). We have previously reported reproducible reductions of NAA in patients with schizophrenia localized to the hippocampal area (HIPPO) and dorsolateral prefrontal cortex (DLPFC). New developments in the hardware of MRI scanners make it now possible to acquire the signal of water along with the metabolites. We have assessed the reproducibility of water-acquired (WA) and water-suppressed (WS) 1 H-MRSI in healthy subjects. Ten healthy subjects underwent two 1 H-MRSI studies with a mean time interval of 17 days. All studies were performed on a 1.5 T GE scanner using a recently developed 1 H-MRSI pulse sequence (van der Veen et al., in press). Two sets of spectra were acquired (WA and WS) in each session in each subject. Metabolite ratios (NAA/CRE, NAA/CHO, CHO/CRE) were measured in several ROIs, including HIPPO and DLPFC. Statistical variability of the data was described using the Coefficient of Variation (CV, standard deviation/ mean). CV for WA data was for HIPPO and DLPFC respectively 12% and 8% for NAA/CRE, 11% and 10% for NAA/CHO, and 13% and 12%. For WS data, the CV for HIPPO and DLPFC was respectively 11% and 12% for NAA/CRE, 12% and 11% for NAA/CHO, 11% and 11% for CHO/CRE. The other ROIs showed similar patterns of variability for all ratios. The present data indicate that WA 1 H-MRSI is at least as reproducible as WS. Data relative to water-normalized ratios will also be presented. 365. EMOTION-INDUCING STIMULI PROCESSING IN ALEXITHYMIA: AN fMRI STUDY S. Berthoz (1,2,3), E. Artiges (1), P.F. Van de Moortele (1), J.-B. Poline (1), S. Rouquette (1), J.L. Martinot (1) (1) INSERM U334 and Service Hospitalier Fre´de´ric Joliot, DSV- CEA, 91 Orsay; (2) CNRS UMR 7593 Hoˆpital de la Salpeˆtrie`re; (3) Psychiatry Department, Broussais Hospital, Paris France Alexithymia is characterized by impairments in emotional awareness and expressiveness. A deficit in anterior cingular cortex (ACC) activation during emotional arousal was hypothesized in alexithymia. Indeed, normal subjects’ emotional awareness was correlated with cerebral blood flow in the ACC, 1 one of those structures involved in emotional experience. We tested this hypothesis in a comparative study of the cerebral regions activated during passive viewing of emotional stimuli in two groups of normal males. These groups were selected among the first and last quartiles of the distribution of the scores of 450 students at a validated scale measuring the ability to identify and communicate emotions. Subjects scored low (n 5 8), or high (n 5 8) on this scale. The stimuli were selected from IAPS 2 according to their valence (positive, negative, neutral) and arousal (high, low) to provide 5 sets of 12 pictures. Control stimuli (“masks”) were created by degrading the initial pictures to suppress their emotional tenors. Cerebral regional activations for pictures were compared to masks, to assess activations unique to emotional content processing. Activations were assessed with a 3Tesla Bruker Imager using blood-oxygen-dependent-level and echo-planar methods. Regional specific effects were analyzed voxelwise (t-values), with SPM99 software. Intergroup comparisons revealed that alexithy- mics had higher activations associated with positive pictures (both high and low arousal), but showed no effect of arousal with negative pictures. Main differences concerned medial prefrontal (BA 9) and anterior cingulate regions. These results further demonstrate that these regions are key structures for emotional processing. (1) J. Cog. Neurosc. 1998,10:525–535 (2) International Affective Pictures System, 1997 366. DECREASED CAUDATE DOPAMINE FUNCTION IN DEPRESSED PATIENTS WITH RETARDED DEPRESSION M.-L. Paille`re-Martinot (1,2), V. Bragulat (2), F. Dolle (2), R. Jouvent (3), J.-L. Martinot (2,4,5) Service de Psychiatrie, Hoˆpital de la Salpeˆtrie`re, 75013 Paris (1); INSERM U334 and Service Hospitalier Fre´de´ric Joliot, DSV-CEA, 91 Orsay (2), France; Service de psychiatrie, Hoˆpital Albert Chenevier, 94000 Cre´teil (4); Service de psychiatrie, Hoˆpital de Biceˆtre, 94270 Le Kremlin-Biceˆtre (5) France An impairment in dopamine transmission has been hypothesized in retarded depressed patients following reports of decreased dopamine 110S Friday Abstracts BIOL PSYCHIATRY 2000;47:1S–173S