Final Report Summary - BRAINIMAGES (How do we keep apart internally generated mental images from externally induced percepts? Dissociating mental imagery, working memory and conscious perception.)
Conscious experiences normally result from the flow of external input into our sensory systems. However, our minds are also able to create conscious percepts in the absence of any sensory stimulation; these internally generated percepts are referred to as mental images, and they have many similarities with real visual percepts; consequently, mental imagery is often referred to as “seeing in the mind’s eye”. Mental imagery is also believed to be closely related to working memory, a mechanism which can maintain “offline” representations of visual stimuli no longer in the observer’s view, as both involve internal representations of previously seen visual attributes. Indeed, visual imagery is often thought of as a conscious window into the content of memory representations. Imagery, working memory, and conscious perception are thus thought to rely on very similar mechanisms. However, in everyday life we are generally able to tell apart the constructs of our imagination from real physical events; this begs the question of how the brain keeps apart internal mental images from externally induced visual percepts. To answer this question, this project isolated the cortical mechanisms associated uniquely with WM and imagery independently of each other and independently of the influence of external conscious percepts. Furthermore, by the use of neuroimaging and brain stimulation, we determined the cortical mechanisms which distinguish between internally generated and externally induced percepts. The results enhanced our understanding of these important processes of human cognition.