Single unit activities were recorded from the lateral geniculate body (LGB) of freely behaving cats to see how the spontaneous firing was altered during the sleep-wakefulness cycle. Identification of the LGB unit was accomplished by stimulating the optic tract with electrical shocks.
1) With 14 LGB units the average discharge rates were measured during sleep and arousal. They were highest during deep sleep (16.4/sec) and decreased from arousal (15.7/sec) to light sleep (10.9/sec).
2) Arousal was associated with well-spaced, continuous discharges of the LGB units and light sleep was characterized with the grouped discharges. The discharge pattern during deep sleep was a mixture of those during arousal and light sleep.
3) The LGB units stopped their spike discharges in phase with the deep sleep wave (DSW) activity and following its subsidence, they fired in burst temporarily.
4) In good recordings it was successful to identify the EPSPs which occurred spontaneously with or without association of the spike discharge. They were decreased in number as the animal fell asleep and were hardly observed when the DSW occurred.
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