ABSTRACT
PURPOSE: Caffeine is the most widely consumed psychostimulant. It is often adopted as a tool to modulate brain activations in fMRI studies. However, its pharmaceutical effect on task-induced deactivation has not been fully examined in fMRI. Therefore, the purpose of this study was to examine the effect of caffeine on both activation and deactivation under sustained attention. MATERIALS AND METHODS: Task fMRI was acquired from 26 caffeine naive healthy volunteers before and after taking caffeine pill (200 mg). RESULTS: Statistical analysis showed an increase in cognition-load dependent task activation but a decrease in load dependent de-activation after caffeine ingestion. Increase of attention and memory task activation and its load-dependence suggest a beneficial effect of caffeine on the brain even though it has no overt behavior improvement. The reduction of deactivation by caffeine and its load-dependence indicate reduced facilitation from task-negative networks. CONCLUSION: Caffeine affects brain activity in a load-dependent manner accompanied by a disassociation between task-positive network and task-negative network.