Electrophysiological properties of intralaminar thalamocortical cells discharging rhythmic () 40 Hz) spike-bursts at ) 1000 Hz during waking and rapid eye movement sleep

Thalamocortical neurons located in the large-celled district of the cat intralaminar centrolateral nucleus were found to discharge spike-bursts with unusually high frequencies (800-1000 Hz) during spindle oscillations of the electroencephalogram. In chronically implanted animals, similar spike-bursts were also fired during wakefulness and rapid eye movement sleep, two behavioral states in which other thalamocortical neurons tonically fire single spikes. Intracellular recordings under barbiturate anesthesia showed that, during spindle oscillations, the spike-bursts of intralaminar neurons are generated by brief low-threshold spikes with a much shorter refractory phase than in other thalamocortical cells. The properties of these neurons make them well suited for the distribution of fast rhythms during arousal and rapid eye movement sleep over the cerebral cortex.