Functional anatomy of high-resolution visual mental imagery.

This study had two purposes. First, in order to address the controversy regarding activation of the primary visual area (PVA) during visual mental imagery, regional cerebral blood flow (rCBF) was recorded while subjects performed a task that required high-resolution visual mental imagery. Second, in order to discover whether verbal descriptions can engage visual mechanisms during imagery in the same way as visual stimuli, subjects memorized 3D scenes that were visually presented or were based on a verbal description. Comparison of the results from the imagery conditions to a non-imagery baseline condition revealed no activation in PVA for imagery based on a verbal description and a significant decrease of rCBF in this region for imagery based on visual learning. The pattern of activation in other regions was very similar in the two conditions, including parietal, midbrain, cerebellar, prefrontal, left insular, and right inferior, temporal regions. These results provide strong evidence that imagery based on verbal descriptions can recruit regions known to be engaged in high-order visual processing.