Cerebral glucose utilization is reduced in second test session

Cerebral glucose utilization was higher during the first positron emission tomography (PET) session than during the second session, as assayed using the PET [ 18 F]fluorode-oxyglucose method in male human volunteers. This difference was due largely to data from subjects with low trait anxiety, since subjects with high anxiety showed similar metabolism in both PET sessions. High-anxiety subjects showed greater right/ left ratios of cerebral metabolism than low-anxiety subjects, particularly during the second PET session. These findings suggest that the level of anxiety may be an important variable to consider in PET studies using multiple sessions.