In single cells of the cat striate cortex, lateral inhibition across orienta(cid:173) tion and/or spatial frequency is found to enhance pre-existing 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, sug(cid:173) gesting that it 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. Analysis of burst patterns in spike trains demonstrates that these two mechanisms have unique physiological origins.
INFORMATION PROCESSING IN STRIATE CORTICAL CELLS
The most popular current model of single cells in the striate cortex casts them in terms of spatial and temporal filters. The input to visual cortical cells from lower visual areas, primarily the LGN, is fairly broadband (e.g., Soodak, Shapley & Kaplan, 1987; Maffei & Fiorentini, 1973). Cortical cells perform significant band(cid:173) width restrictions on this information in at least three domains: orientation, spatial frequency and temporal frequency. The most interesting quality of these cells is 75