["Timer" neurons and "scanner" neurons in the visual cortex of the cat in response to low-contrast between stimulus...

The characteristics of the reactions and the properties of orientation detection in neurons separated formerly into "timers" and "scanners" at a high contrast (100) were studied in experiments on unanesthetized, relaxed cats at a lower contrast level. It was found that all "scanners" preserved their properties and did not pass to the group of "timers". On the other hand, only 40% of the initial number of the "timers" remained in this group. Correlation of the properties of neurons of these groups remained as it was at maximum contrast: in "timers" the reaction began and reached the maximum earlier than in "scanners"; it was of a higher frequency and shorter and its characteristics of the orientation tuning were considerably worse. Neurons which passed from the group of "timers" at the lower contrast possessed characteristics intermediated between those of the "timers" and "scanners", approaching the latter by a number of properties. The obtained data confirm the conclusion about the presence and stability of the activity of the visual cortex neurons--"timers" and "scanners" within a wide range of conditions; the former carry out the function of synchronizers, the latter--the role of orientation filters reforming in time.