Mental Processes and the Brain During Dreams

This article examines the different theoretical approaches to dreaming and compares them with recent data from brain-mapping studies. Two lines of investigation were considered: a neurobiological and a cognitive approach. Both lines of investigation can be usefully integrated into recent research using the techniques of brain mapping. Two aspects of particular interest are discussed: (a) The pattern of limbic and paralimbic activation in rapid eye movement (REM) and non-REM could explain some differences of oneiric hallucination during different stages of sleep, and (b) the deactivation of the heteromodal cortex could explain the loss of reality testing and the absence of self-consciousness during dreams. The complex nature of the dreaming phenomenon makes it necessary to distinguish clearly between mental representation and the underlying neurobiological changes.