Dual Inhibitory Mechanisms for Definition of Receptive Field Characteristics in a Cat Striate Cortex

In single cells of the cat striate cortex, lateral inhibition across orientation and/orspatial frequency is found to enhance preexisting biases. A contrast-dependent but spatially non-selective inhibitory component is also found. Stimulation with ascending and descending contrasts reveals the latter as a response hysteresis that is sensitive, powerful and rapid, suggesting thatit is active in day-to-day vision. Both forms of inhibition are not recurrent but are rather network properties. These findings suggest two fundamental inhibitory mechanisms: a global mechanism that limits dynamic range and creates spatial selectivity through thresholding and a local mechanism that specifically refines spatial filter properties.