The aim of the study is to investigate the biological function of dreaming, which is different from that of REM sleep. Humans spend nearly one-third of each day asleep. During approximately one-fifth of this time, they dream. This means that about 90 minutes a day are spent in a state of dreaming. It is therefore surprising that neither empirical sleep research nor neuroscientific studies have yet been able to comprehensively clarify the biological function of dreaming. The question remains: Why do we actually dream?
By specifically choosing a sample of neurological patients with posterior cortical lesions who are at risk of losing the ability to dream due to the lesion, the proposed project specifically aims to understand the biological function of dreaming as distinct from REM sleep. Based on the neuropsychoanalytic theory of Solms (1997), as well as neuropsychological findings that REM sleep and dreaming are double dissociable phenomena, the central hypothesis that dreams serve to maintain sleep (Freud's hypothesis, see Freud,  2000) will be investigated. By this, Freud meant that dreams serve to respond to sometimes highly affect-laden impulses to action with hallucinatory wish fulfillment, so that they do not lead to premature awakening. Second, we will investigate whether dreams influence affective memory consolidation. Our hypotheses are that patients who have lost the ability to dream while maintaining REM sleep will have (i) poorer sleep quality and (ii) poorer emotional declarative memory consolidation.