ABSTRACT
The pathway for visual perception commences with the retinogeniculate fibers, axons of ganglion cells that end in the lateral geniculate nucleus (LGN). LGN cells have circular receptive fields (RFs) with surround antagonism. They show little or no response to diffuse light covering the whole receptive field. The fibers of the optic tract terminate in the striate cortex on the medial surface of the tip of the occipital lobe. This region is the primary visual cortex. Precise retinotopic mapping is maintained up to V1 with the fovea having a disproportionate representation. Computer modeling shows that orientation selectivity is a property of neural networks that learn the curvature of curved surfaces from their shading. Hence orientation selectivity might, counter intuitively, be concerned with representations of curves than linear features in the visual world. Columns representing ipsilateral and contralateral input alternate regularly over the cortex which, when visualized at the level of layer 4C, looks like the pattern of stripes on a zebra.
