Functional Anatomy of High-Resolution Visual Mental Imagery

TLDR

The study aimed to determine whether primary visual area activation occurs during high‑resolution visual mental imagery and whether verbal descriptions can engage visual mechanisms similarly to visual stimuli. Regional cerebral blood flow was measured while participants performed high‑resolution visual mental imagery of 3D scenes learned either visually or from verbal descriptions. Verbal‑description imagery showed no primary visual area activation and reduced rCBF, while visual‑learning imagery also decreased rCBF in PVA, yet both conditions activated similar high‑order visual regions, demonstrating that verbal descriptions can recruit high‑order visual processing areas.

Abstract

Abstract 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.