Why do imagery and perception look and feel so different?

Abstract

Despite the past few decades of research providing convincing evidence of the similarities in function and neural mechanisms between imagery and perception, for most of us, the experience of the two are undeniably different, why? Here, we review and discuss the differences between imagery and perception and the possible underlying causes of these differences, from function to neural mechanisms. Specifically, we discuss the directional flow of information (top-down versus bottom-up), the differences in targeted cortical layers in primary visual cortex and possible different neural mechanisms of modulation versus excitation. For the first time in history, neuroscience is beginning to shed light on this long-held mystery of why imagery and perception look and feel so different. This article is part of the theme issue 'Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.

Keywords: feedback signals; mental imagery; perception.

Figure 1.

Prospective view of the cortical layers targeted by feed-forward and feedback in V1. While results are preliminary and need more validation, based on current evidence, feed-forward connections primarily target the middle layer, while feedback signals derived from the processing of visual perception seem to target superficial layers of V1. On the other hand, feedback signals triggered by internally generated representations appear to target deep cortical layers of V1. (Online version in colour.)