Dreaming is characterized by formal visual imagery (akin to hallucinat
ion), by inconstancy of time, place and person (akin to disorientation
), by a scenario-like knitting together of disparate elements (akin to
confabulation) and by an inability to recall (akin to amnesia). Taken
together, these four dream features are similar to the delirium of or
ganic brain disease. By studying the brain during rapid-eye-movement (
REM) sleep - the phase of sleep in which most dreaming occurs - we can
begin to understand its basis in the altered neurophysiology of REM.