The authors compared 16 nondepressed obsessive-compulsive patients (OCS) with 8 normal controls (NC) of similar age for resting-state regional cerebral glucose metabolic rates (rCMRglu) using positron emission tomography with the fluorodeoxyglucose method. OCS were rated for clinical data, and a neuropsychological battery was administered to 14 patients on the day of the scan. Absolute rCMRglu for whole cortex, and normalized prefrontal lateral cortex metabolic rates, were both significantly lower in OCS than in NC. No significant difference between treated (n = 10) and drug-free (n = 6) OCS was found for those variables. OCS were significantly impaired in the neuropsychological tasks assessing memory and attention. The rCMRglu for prefrontal lateral cortex were negatively correlated to Stroop-test subscores. This "frontal-oriented" task assessed the ability of OCS to inhibit immediate but inappropriate responses. These results suggest, in OCS, a modification of the general activating systems of cortical function and a relationship between the lateral prefrontal rCMRglu decrease and a selective attention deficit.

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SummaryThe cortical metabolic patterns of 12 schizophrenics experiencing hallucinations and/or pseudo-hallucinations were investigated using positron tomography and 18F-fluoro-deoxy-glucose. Andreasen's scales were scored and the patients (all “mixed“) were classified in a “positive” or a “negative” group and compared to a group of 6 normal controls. The data were analyzed across groups for absolute metabolic rates, metabolic indices (cortical region/whole studied cortex), and specific indices exploring the sensory non-association/posterior parietal association and the prefrontal association/posterior parietal association dimensions. Whole-cortex metabolic rate in the negative group was found to be lower than both the control (P=0.02) and the positive group (P = 0.002) while the positive group did not differ significantly from the controls. We found “hypofrontality” to be without difference between the positive and the negative group (controls: 7±0.7, positive: 5.9±0.2, negative: 4.9±0.15, mean±SEM in mg/min/100 g). However, the prefrontal association/posterior parietal association ratio was increased in the negative group (P=0.02). A major finding was an increase in the posterior non-association/posterior parietal association ratio in the whole schizophrenic group as compared to the controls (P = 0.004), this being more marked in the negative (P=0.01) than in the positive group. Arguments are given to support the hypothesis that this particular increase could be related to the hallucinatory activity of the patients.

SummaryThe striatal D2 receptor density/affinity index was assessed using positron emission tomography and 76Br-Bromolisuride in 15 schizophrenics, first untreated, and afterwards receiving neuroleptics, and in 14 control subjects. The patients received low or conventional doses of neuroleptics. The schizophrenics receiving low doses (n = 6) had preponderant negative symptoms. Mean D2 receptor occupancy was 24 ± 20%. Despite this weak central D2 receptor blockade, a significant decrease in negative symptoms was observed, a result consistent with the hypothesis of a disinhibitory action of some neuroleptics administered in low doses. The patients treated with conventional doses (n = 9) had mixed positive and negative symptoms, and the mean D2 receptor occupancy was 54 ± 13%. Significant decreases in positive symptoms, but also in negative symptoms, were obtained with this treatment. Before treatment, there was no significant difference in the striatal D2 receptor density/affinity index between: 1) patients and controls, 2) negative and mixed schizophrenics, and 3) the subsequent responder and non-responder patients. In addition, the D2 dopamine receptor occupancy by neuroleptics did not significantly differ in responder or nonresponder patients, suggesting that the central D2 dopamine receptor blockade is a necessary, but insufficient condition to account for the antipsychotic effect of neuroleptics.

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