Single cell activity in area 18 of the cat's visual cortex during optokinetic nystagmus.

Single cell activity was recorded in area 18 during optokinetic nystagmus (OKN) in awake cats. The search coil technique was used to record the horizontal and vertical eye movements. Cells showing direction specific responses to a moving large area random dot pattern (70%) were tested with different velocities in the preferred and in the null-direction. Their response characteristics can be classified according to the two phases of the OKN. 41% responded specifically to the retinal slip velocity, having their response optimum at different values between 2 and 100 degrees/s. Additionally, in 60% of all tested cells the resetting saccades of the OKN were correlated with brief activity bursts of 39 ms latency on the average. These results are discussed in terms of two concepts: the classic concept of a corollary discharge from the oculomotor system and the concept of a gating function of the reticular system on thalamic and cortical transmission.