Effect of certain cerebral hemispheric diseases on dreaming.

Dreaming may be altered by cerebral hemispheric disease. A woman who sustained a probable left posterior cerebral artery thrombosis, with right homonymous hemianopsia and alexia, had virtual cessation of dreaming for at least 9 months. Four individuals with temporal lobe epilepsy experienced recurrent painful (frightening) dreams, which in two patients showed features identical to seizures. Sleep recordings showed abnormalities in all four, including rhythmic temporal epileptiform activity during REM sleep. Lesions in parieto-occipital loci may interfere with production of the visual imagery required for dreaming (negative symptom in the Jacksonian sense) while epileptic activity in temporal loci may produce painful repetitive dream imagery (positive symptom).