Under conditions of moderate alcohol intoxication (0.75 ml/kg) and an alcohol-disguised placebo, eight non-alcoholic male volunteers performed a divided attention task after injection of 18-F-2-fluoro-2-deoxyglucose (FDG) for a Positron Emission Tomography (PET) study. The administration of alcohol or placebo followed a random order double-blind protocol. During 32 min of divided attention, the subject performed a letter matching task or a spatial orientation task presented simultaneously on a computer-generated split display. The task to be performed was indicated by an arrow on the display that changed randomly every few trials. Alcohol intoxication was associated with a trend toward generally reduced performance. Task performance differences between the alcohol and placebo conditions were significantly correlated with cortical glucose metabolic rates (GMR) in the superior, inferior, and middle parietal lobes. Impaired performance was associated with GMR decreases. GMR in several subcortical and medial cortical areas were also correlated with performance changes, including areas of the putamen and cingulate. The major finding is that individual differences in GMR change from placebo to alcohol in parietal cortex are related to individual differences in attention performance. The application of PET with selective information processing paradigms provides a useful method for isolating and in identifying the effects of alcohol intoxication on the function of the central nervous system.

Regional cerebral glucose metabolic rate (GMR) quantified with positron emission tomography (PET) with 18-fluoro-2-deoxyglucose (FDG) was measured twice in 8 young men performing a complex visuospatial/motor task (the computer game Tetris), before and after practice. After 4-8 weeks of daily practice on Tetris, GMR in cortical surface regions decreased despite a more than 7-fold increase in performance. Subjects who improved their Tetris performance the most after practice showed the largest glucose metabolic decreases after practice in several areas. These results suggest that learning may result in decreased use of extraneous or inefficient brain areas. Changes in regional subcortical glucose metabolic rate with practice may reflect changes in cognitive strategy that are a part of the learning process.