[Neurological interpretation of dreams] .

Cerebral cortical activity is constant throughout the entire human life, but substantially changes during the different phases of the sleep-wake cycle (wakefulness, non-REM sleep and REM sleep), as well as in relation to available information. In particular, perception of the environment is closely linked to the wake-state, while during sleep perception turns to the internal domain or endogenous cerebral activity. External and internal information are mutually exclusive. During wakefulness a neuronal mechanism allows attention to focus on the environment whereas endogenous cortical activity is ignored. The opposite process is provided during sleep. The function external attention-internal attention is coupled with the two modes of brain function during wakefulness and during sleep, providing two possible cortical status: thinking and dreaming. Several neurological processes may influence the declaration of the three states of being or may modify their orderly oscillation through the sleep-wake cycle. In addition, endogenous information and its perception (dreams) may be modified. Disturbances of dreaming may configurate in different general clinical scenarios: lack of dreaming, excess of dreaming (epic dreaming), paroxysmal dreaming (epileptic), nightmares, violent dreaming, daytime-dreaming (hallucinations), and lucid dreaming. Sensorial deprivation, as well as the emergence of internal perception may be the underlying mechanism of hallucinations. The probable isomorphism between hallucinations and dreaming is postulated, analyzed and discussed.