Distinct Top-down and Bottom-up Brain Connectivity During Visual Perception and Imagery

TLDR

Research suggests that perception and imagination engage neuronal representations in the same visual areas, yet the mechanisms that differentiate sensory perception from imagination remain unclear. The study examines directed coupling between fronto‑parietal and visual areas during perception and imagery. Effective connectivity was assessed by measuring directed coupling between fronto‑parietal and visual regions during both tasks. Bottom‑up coupling increased during perception, while top‑down coupling increased during both perception and imagery—especially during imagery—and stronger top‑down connectivity to early visual cortex correlated with vividness, underscoring the importance of top‑down processing in visual experience.

Abstract

Research suggests that perception and imagination engage neuronal representations in the same visual areas. However, the underlying mechanisms that differentiate sensory perception from imagination remain unclear. Here, we examine the directed coupling (effective connectivity) between fronto-parietal and visual areas during perception and imagery. We found an increase in bottom-up coupling during perception relative to baseline and an increase in top-down coupling during both perception and imagery, with a much stronger increase during imagery. Modulation of the coupling from frontal to early visual areas was common to both perception and imagery. Furthermore, we show that the experienced vividness during imagery was selectively associated with increases in top-down connectivity to early visual cortex. These results highlight the importance of top-down processing in internally as well as externally driven visual experience.