The vision of dreams: from ontogeny to dream engineering in blindness
The mechanisms involved in dreams’ origin remain one of the great unknowns in science. In the twenty-first century, studies in the field have focused on three main topics: functional networks that underlie dreaming, neural correlates of dream contents, and signal propagation. We review neuroscientific studies about dreaming processes, focusing on their cortical correlations. The involvement of frontoparietal regions in the dream-retrieval process allows us to discuss it in light of the Global Workspace theory of consciousness. However, dreaming in distinct sleep stages maintains relevant differences suggesting that multiple generators are implicated. Then, given the strong influence of light perception on sleep regulation and the mostly visual content of dreams, we investigate the effect of blindness on dreams’ organization. Blind individuals represent a worthwhile population to clarify the role of perceptual systems in dreams’ generation, and to infer about their top-down and/or bottom-up origin. Indeed, congenitally blind people maintain the ability to produce visual dreams, suggesting that bottom-up mechanisms could be associated with innate body schemes or multisensory integration processes. Finally, we propose the new dream engineering technique as a tool to clarify the mechanisms of multisensory integration during sleep and related mental activity, presenting possible implications for rehabilitation in sensory-impaired individuals. Theory of Protoconsciousness suggests that the interaction of brain states underlying waking and dreaming ensures the optimal functioning of both. Therefore, understanding the dreams’ origin and capabilities of our brain during a dreamlike state, we could introduce it as a rehabilitative tool.