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Patients in inpatient rehabilitation for uncomplicated cocaine dependence were asked whether, compared with the time of their first regular use, they could now identify changes in the effects of similar doses of cocaine. We asked about a spectrum of cocaine effects "then" and "now" and whether the same amount of drug caused effects to occur to about the same degree, less intensely (tolerance), or more intensely (sensitization). Nearly half our sample developed predominantly paranoid psychoses in the context of cocaine use. Sensitization was consistently linked only to psychosis-related cocaine effects. It has been proposed that mesolimbic dopaminergic sensitization might contribute to addiction severity. A preliminary followup of patients who were sensitized or nonsensitized to psychosis development suggests that rehospitalization for treatment of addiction may be more frequent in the sensitized group.

Summary: Positron emission tomography with IlC-2-de oxyglucose was used to determine the test-retest vari ability of regional cerebral glucose metabolism in 22 young normal right-handed men scanned twice in a 24-h period under baseline (resting) conditions. To assess the effects of scan order and time of day on variability, 12 subjects were scanned in the morning and afternoon of the same day (a.m.-p.m.) and 10 in the reverse order (p.m.-a.m.) with a night in between. The effect of anxiety on metabolism was also assessed. Seventy-three percent of the total subject group showed changes in whole brain metabolism from the first to the second measurement of 10% or less, with comparable changes in various cortical and subcortical regions. When a scaling factor was used to equate the whole brain metabolism in the two scans for each individual, the resulting average regional changes Positron emission tomography (PET) with deoxy glucose is now a generally accepted method of measuring regional brain glucose metabolism (Rei vich and Alavi, 1985;Phelps et al. 1986). In many studies, the effect of some stimulation is ascer tained in comparison with baseline metabolism in a test-retest repeated-measure design. However, to have some assurance that the difference between the two measurements or runs is a valid estimate of the effect of stimulation, one must have some knowledge of the reproducibility of the baseline Abbreviations used: PET, positron emission tomography; CDG. Ilc-2-deoxyglucose; ROI, region of interest; CT, com puted axial tomography; RCMRG, regional cerebral metabolic rate for glucose; CMRG, cerebral metabolic rate for glucose; MANOVA, multivariate analysis of variance. 502for each group were no mote than 1 %. This suggests that the proportion of the w h ole brain metabolism utilized re gionally is sta bl e in a group of subjects over time. Both groups of subjects had lower morning than afternoon me tabolism, but the differences were slight in the p.m.-a,m. group. One measure of anxiety (pulse at fUll 1) was cor related with run 1 metabolism and with the percentage of change from run 1 to run 2. No significant run 2 correla tions were observed. This is the first study to measure test-retest variability in cerebral glucose metabolism in a large sample of young normal subjects. It demonstrates that the deoxyglucose method yields Itlw i ntrasubject variability and high stability OVer a 24-h period. Key Words: PET -Reprodue ibi lity -Brain, metabolismDeoxyglucose.

Two tasks were used to test predictions of the Semantic Feature Hypothesis (SFH) about children's comprehension of the meaning of spatial adjectives. Our data support SFH predictions about the order of acquisition for dimensional features: more general features are acquired first. Predictions about polarity, however, were not supported: our data show that children do not acquire [+ pol] features prior to their [− pol] counterparts. Type of task made no difference in children's comprehension of [+ pol] terms but did affect comprehension of [− pol] terms. To account for this pattern of results, an acquisition hypothesis is offered which, contrary to the SFH, proposes that polar features are acquired prior to dimensionality and that semantic features may be added quite independently to [+ pol] and [− pol] terms.

The metabolic response to drug challenge separates treatment responders from nonresponders and normal subjects. The results suggest that subtyping of schizophrenia (and other psychiatric disorders) can be achieved by measuring the physiologic response to a pharmacologic challenge in vivo with chemical brain-imaging techniques.

Positron emission tomography (PET) and the deoxyglucose method were used to measure cerebral metabolism in 14 normals and 13 schizophrenics at rest and during performance of simple and complex finger-movement sequences. The normals, but not the schizophrenics, showed significant metabolic activation in mesial frontal and contralateral sensorimotor and premotor regions during the complex movement. The relative metabolism of schizophrenics was significantly lower than normal in frontal regions and higher than normal in thalamus and basal ganglia under all scanning conditions. The results suggest that schizophrenics may have a brain dysfunction which limits their capacity to produce a focal metabolic response to stimulation in several functionally distinct brain regions.

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