[What image characteristics are selected by neurons in the cat primary visual cortex?].
About 40% of neurons (114/289) studied in the cat area 17 gave a larger (by 3.06 +/- 0.32 times on average) response to a flashed cross, corner or y-like figures centered in the RF than to an optimal single bar. Most such neurons (72%) were found to be highly selective both to shape (angle between the lines) and to orientation of these figures. In the studied neuronal selection we have also found all possible types of invariance of sensitivity to orientation and/or shape of these figures. Separated and combined stimulation of RF center and surrounding area revealed in 44 units summation, antagonism or absence of interaction of these zones by the selectivity index (cross/bar response ratio). Cross-sensitivity was investigated in 85 V1 neurons before, during and after local blockade of GABAA ergic inhibition by microiontophoretical application of bicuculline. Inhibition either emerged or increased cross-sensitivity (32% of cells), or depressed it (36% of cases), while in some neurons it does not influenced the function. Possible mechanisms of the described effects are discussed as well as their functional implication for second-order feature extraction in the visual cortex: selective or invariant sensitivity of neurons to the shape and orientation of the line-crossings.
Shevelev
I A
IA
Institute of Higher Nervous Activity and Neurophysiology, Russian Acad. Sciences, Moscow, Russia.
D000818:Animals; D002415:Cats; D005556:Form Perception / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D010775:Photic Stimulation; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*