[Differences in the properties of 2 groups of orientation detectors of the visual cortex in the cat]

Functional properties of 149 neurons in field 17 of the visual cortex were studied in immobilized cats. They were divided into two groups. In 37% of neurons the initial and peak latencies of responses changed not more than by 10 ms in the orientation range. They were named "timer"-neurons. 63% of neurons were called "scanners". "Timers" reliably differed from "scanners" in shorter latencies, time of the discharge frequency increase, duration of the response and higher discharge frequency in all stimuli orientations. Scanners had a higher orientation selectivity, they considerably more often scanned the range of orientations in time. Neurons of the two groups had contraphase dynamics of the width of tuning orientation during response while distribution of their preferential orientations supplemented each other. In orientation columns of the visual cortex, both timers and scanners were most often found with a predominance of the latter. The columns consisting of only timers or only scanners were more seldom. The role of differences in properties of two neuronal groups in the cat visual cortex for orientation detection is discussed.