No abstract

These results provide the first link between age-related declines in brain dopamine activity and frontal and cingulate metabolism, which supports the need to investigate the therapeutic utility of interventions that enhance dopamine function in the elderly. The fact that correlations remained significant after removing age effects suggests that dopamine may influence frontal, cingulate, and temporal metabolism regardless of age.

The cerebral mechanisms underlying excess food intake in obese subjects are poorly understood. We used PET and 2-deoxy-2[18F]fluoro-D-glucose to assess differences in regional brain metabolism between obese and lean subjects at rest. Brain metabolic images were analyzed using statistical parameter maps. We found that obese subjects have significantly higher metabolic activity in the bilateral parietal somatosensory cortex in the regions where sensation to the mouth, lips and tongue are located. The enhanced activity in somatosensory regions involved with sensory processing of food in the obese subjects could make them more sensitive to the rewarding properties of food related to palatability and could be one of the variables contributing to their excess food consumption.

These results support similar though not identical mechanisms for the effects of alcohol and benzodiazepines on brain glucose metabolism. The fact that lorazepam, but not alcohol, reduced thalamic metabolism, an effect associated with sleepiness, could explain the higher sedative effects of lorazepam than of alcohol.