Imageless imagery in aphantasia revealed by early visual cortex decoding.

Activity in the primary visual cortex is thought to be closely linked to conscious visual experience, including mental imagery. In people with aphantasia, who lack visual imagery entirely, researchers examined brain activity during attempts to imagine. Neural patterns representing imagined content could be decoded equally well in both groups, but in aphantasia the signals were located on the same side of the brain as the stimulus and could not be matched to perceptual brain patterns. Additionally, the brain response to actual visual input was weaker in aphantasia. These findings suggest that imagery-related representations exist in primary visual cortex even without conscious visual experience, challenging the assumption that such activity necessarily produces sensory qualia.

Study at a glance

Abstract

Activity in the early visual cortex is thought to tightly couple with conscious experience, including feedback-driven mental imagery. However, in aphantasia (a complete lack of visual imagery), the state of mental imagery, what takes its place, or how any activity relates to qualia remains unknown. This study analyzed univariate (amplitude) and multivariate (decoding) blood-oxygen-level-dependent (BOLD) signals in primary visual cortex during imagery attempts. "Imagery" content could be decoded equally well in both groups; however, unlike in those with imagery, neural signatures in those with validated aphantasia were ipsilateral and could not be cross-decoded with perceptual representations. Further, the perception-induced BOLD response was lower in those with aphantasia compared with controls. Together, these data suggest that an imagery-related representation, but with less or transformed sensory information, exists in the primary visual cortex of those with aphantasia. Our data challenge the classic view that activity in primary visual cortex should result in sensory qualia.