| Abstract: | Variability of orientation tuning of primary visual cortical neurons in single orientation columns and the degree of its stability during changes in the level of contrast between stimulus and background were investigated in acute experiments on immobilized cats. Several types of orientation columns were found, with the following properties of orientation tuning of their neurons: relatively high, standard, and stable; varying widely from neuron to neuron; invariant regardless of the level of contrast; noninvariant; mixed (invariant-noninvariant). Properties of standardization-nonstandardization, on the one hand, and invariance-noninvariance of the neurons, on the other hand, may be combined differently in a column. Differences of orientation tuning within a column were observed most frequently in neurons of the upper and lower layers of the cortex. Possible differences in the functional role of the variance of orientation columns described and in the mechanisms of formation of the detector properties of their neurons are discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 2, pp. 175–182, March–April, 1985. |
