PURPOSE: Orientation selective is an emergent property of primary visual cortex (V1). Previous studies have proposed that broadly-tuned suppression or response nonlinearity (power law) may play important roles for sharpening of cortical selectivity. We ask how the two mechanisms collaborate to sharpen the orientation selectivity in V1.
METHODS: we used a linear array electrode to record neural response simultaneously from multiple cortical depths in V1 of awake macaque monkeys. Stimuli with different orientations flashed 20ms each frame. Dynamic responses was calculated with the reverse correlation method.
RESULTS & CONCLUSIONS:We found that dynamic responses to stimulus orientations are different cross cortical layers. Based on the response dynamics, we estimate the broadly-tuned suppression and response nonlinearity at different layers, we found that suppression is stronger in input layers, while output layers have largest nonlinearity and highest selectivity. Our results suggest that orientation selectivity is sharpened through multiple stages in V1.