[Dynamics of orientational tuning of visual cortex neurons in the cat]

Orientational tuning of singly units in the primary visual cortex of a nonanesthetized paralyzed cat was studied by usual criteria (number of spikes and maximal frequency of the response) and by "time slices" method. A computer plotted graphs of orientational tuning for successive time intervals with a step of 10 or 20 ms (differential slices) or for prolonged intervals with same step (integral slices). In both cases it was revealed that in all the investigated units orientational tuning markedly changed in time, most often in wideness of characteristic and in 87% of cases in preferred orientation range was detected: preferred orientation systematically moved for 15-112 degrees in successive moments during some tens of ms of the first and the second burst of spikes. A possible functional significance of the data revealed and the neurophysiological mechanisms are discussed.