Dreaming: A neurological view

Abstract

Dreaming is the mental activity of REM (and less commonly NREM) sleep. It is characterised by a perception of self, inner and outer world that is distinct from that of wakefulness. Neurophysiological and neuroimaging studies suggest that dreaming arises from activation of brainstem, thalamo-limbic and medial temporo-occipital areas and inactivation of dorsolateral prefrontal areas. Dream abnormalities in neurological disorders have poorly been studied. They include a reduction/cessation of dreaming (Charcot-Wilbrand syndrome), an increase in dream frequency, changes in dream contents and accompaniments (including REM sleep behaviour disorder) and the occurrence of dream-like experiences (hallucinations) during wakefulness and wake-sleep/sleep-wake transitions. Dream changes in association with neurological conditions including primary sleep disorders (e.g. narcolepsy, REM sleep behaviour disorder [RBD], nightmares), stroke and Parkinson's syndrome are reviewed. Assessment of altered dreaming and dream-like experiences can be of clinical significance because of their diagnostic and therapeutic implications (RBD, hallucinations), prognostic significance (hallucinations) and distress that they can have for patients and their bed partners (e.g. nightmares, hallucinations, RBD). In addition, systematic studies of dream and dream-like experiences are expected to offer unique insights into the brain, mind and emotions of neurological patients.