Unconscious Imagination and the Mental Imagery Debate

Summary

Mental imagery and visual perception may not rely on the same brain mechanisms as traditionally thought. While some evidence from brain stimulation suggests overlap, studies of brain-damaged patients show that people can lose mental imagery without losing perception, and vice versa. This review argues that conscious visual imagery and vision-for-perception use distinct mechanisms, but vision-for-action and unconscious visual imagery share overlapping mechanisms. The authors propose modifying Kosslyn's model of imagery to include unconscious imagination and explore how conscious visual imagery can feel picture-like even though its neural basis differs from that of visual experience.

Study at a glance

Abstract

Traditionally, philosophers have appealed to the phenomenological similarity between visual experience and visual imagery to support the hypothesis that there is significant overlap between the perceptual and imaginative domains. The current evidence, however, is inconclusive: while evidence from transcranial brain stimulation seems to support this conclusion, neurophysiological evidence from brain lesion studies (e.g., from patients with brain lesions resulting in a loss of mental imagery but not a corresponding loss of perception and vice versa) indicates that there are functional and anatomical dissociations between mental imagery and perception. Assuming that the mental imagery and perception do not overlap, at least, to the extent traditionally assumed, then the question arises as to what exactly mental imagery is and whether it parallels perception by proceeding via several functionally distinct mechanisms. In this review, we argue that even though there may not be a shared mechanism underlying vision for perception and conscious imagery, there is an overlap between the mechanisms underlying vision for action and unconscious visual imagery. On the basis of these findings, we propose a modification of Kosslyn's model of imagery that accommodates unconscious imagination and explore possible explanations of the quasi-pictorial phenomenology of conscious visual imagery in light of the fact that its underlying neural substrates and mechanisms typically are distinct from those of visual experience.