Forebrain Inhibitory Mechanisms: Sleep Patterns Induced by Basal Forebrain Stimulation in the Behaving Cat

Abstract Adult cats were prepared with indwelling bipolar strut electrodes placed stereotaxically into a specific basal forebrain area. The effects of stimulating this area were described in a previous study employing acute immobilized cat preparations, and ability to induce a diffuse electroencephalographic synchronization when stimulated was stressed. The effective zone is bilateral and is situated at the base of the brain, just rostral to the optic chiasma, and has been termed the basal forebrain synchronizing area. The purpose of the present study was to determine the behavioral response to stimulation at this site, simultaneously recording electroencephalographic activity. After a postoperative recovery period, animals were tested periodically for several months in a large isolated behavioral cage. Bilateral stimulation of this area in the behaving cat resulted in the behavioral and electroencephalographic manifestations of sleep in every animal tested. The transition from alert waking behavior to sleep occurred rapidly—usually in less than 1 min—and took place either during one prolonged stimulation period or several short periods of stimulation. Both low and high frequency stimulation (5–250 impulses per sec) were effective in producing the postural adjustments, electroencephalographic patterns, and response reversability observed in the onset of natural sleep.