Sleeping dreams, waking hallucinations, and the central nervous system.

Abstract

Consciousness is now considered a primary function and activity of the brain itself. If so, consciousness is simply the brain's interpretation and integration of all the information made available to it at any given time. On the assumption that the brain is active across all states of being (wakefulness, REM sleep, and NREM sleep), this article proposes that dreaming and hallucinations represent variations on the same theme. Under usual circumstances during wakefulness, the brain ignores internally generated activity and attends to environmental sensory stimulation. During sleep, dreaming occurs because the brain attends to endogenously generated activity. In unusual settings, such as sleep-deprivation, sensory deprivation, or medication or drug ingestion, the brain attends to exogenous and endogenous activities simultaneously, resulting in hallucinations, or wakeful dreaming. This concept is supported by numerous neurologic conditions and syndromes that are associated with hallucinations.