"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 keep apart the constructs of our imagination from real physical events; this begs the question of how the brain distinguishes internal mental images from externally induced visual percepts. To answer this question, the proposed work aims to isolate 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 aim to determine the cortical mechanisms which keep apart internally generated and externally induced percepts, in both health and disease. This is a question of great clinical interest, as the ability to distinguish the perceived from the imagined is impoverished in psychotic disorders. In addition to revealing the mechanisms underlying this confusion, the present project aims to alleviate it in psychotic patients by the use of brain stimulation. The project will thus significantly improve our understanding of these cognitive processes and will also have clinical implications."