Semantic and emotional content of imagined representations in human occipitotemporal cortex

Daniel J Mitchell,Rhodri Cusack

doi:10.1038/srep20232

Abstract

Mental imagery is a critical cognitive function, clinically important, but poorly understood. When visual objects are perceived, many of their sensory, semantic and emotional properties are represented in occipitotemporal cortex. Visual imagery has been found to activate some of the same brain regions, but it was not known what properties are re-created in these regions during imagery. We therefore examined the representation during imagery for two stimuli in depth, by comparing the pattern of fMRI response to the patterns evoked by the perception of 200 diverse objects chosen to de-correlate their properties. Real-time, adaptive stimulus selection allowed efficient sampling of this broad stimulus space. Our experiments show that occipitotemporal cortex, which encoded sensory, semantic and emotional properties during perception, can robustly represent semantic and emotional properties during imagery, but that these representations depend on the object being imagined and on individual differences in style and reported vividness of imagery.

Highlights

Mental imagery is a critical cognitive function, clinically important, but poorly understood
Mental imagery is disturbed in many clinical conditions such as neglect[12,13,14], tunnel vision[15], schizophrenia[16,17] and William’s Syndrome[18], and can be debilitating when uncontrolled, in post-traumatic stress disorder and phobia[19,20]
The remaining variance will reflect a mixture of other object features encoded in higher dimensions, and measurement noise, which will be substantial in the response at the level of single images given the large number of stimuli (200) but low number of repetitions.)

Summary

Introduction

Mental imagery is a critical cognitive function, clinically important, but poorly understood. Mental imagery has seen increasing use as a therapeutic technique to treat emotional disorders[19,20], and as a clinical tool to assess conscious awareness when behavioural responses are unavailable[21] Despite this fundamental role in cognition, and increasing clinical importance, the information content that is represented during mental imagery remains elusive. In occipitotemporal cortex, classifiers trained on activity patterns evoked by perceived items were able to successfully classify imagined items, and vice-versa This demonstrates that occipitotemporal cortex represents some common information across perception and imagery, the nature of the shared information remains unclear. During perception, this region encodes a range of both simple sensory and higher-level object properties[29,30,31,32]. This allowed us to investigate which www.nature.com/scientificreports/

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Conclusion