Interrelation of tuning characteristics to bar, cross and corner in striate neurons

Abstract

Characteristics of responses and background activity, as well as of tuning to a single bar orientation and to cross or corner shape and orientation have been compared in one third (56/174) of neurons in the cat striate cortex. Shortening of the response latency to cross vs bar, to corner vs bar and to corner vs cross was revealed in most of the units studied. Direct correlation between the response and tuning characteristics for bar, cross and corner was revealed: units with better tuning to one type of stimulus were typically better tuned to the other types of stimuli. At the middle cortical depth (700–1 200 μm from the surface) we found a reliable improvement of response magnitude and latency, cross/bar response ratio and selectivity of tuning in comparison with more superficial and deeper layers. Although we could not find a direct correlation between characteristics of tuning to figures and the type of the receptive field (simple, complex or hypercomplex), our data pointed to a lower cross/bar ratio and selectivity of tuning in the units with small receptive fields. The functional implication of neuronal sensitivity to cross and corner and possible meaning of correlation between their functional characteristics are discussed.