Showing papers on "Orientation column published in 1967"

Comparison of the effects of striate cortex and retinal lesions on visual acuity in the monkey.

Abstract: Acuity falls sharply and predictably in man as fixation is shifted away from the test stimulus. If the same "eccentricity" function applies to the monkey, then it can be shown that striate cortex lesions produce a smaller acuity impairment than is predicted by electrophysiological maps of the projection of retina onto the cortex. It is seen in this study that retinal lesions of the fovea and adjacent parafovea produce a more severe drop in acuity than corresponding cortical lesions, and therefore the surprisingly slight effects of the latter cannot be explained in terms of a relatively higher parafoveal acuity in the monkey. The discrepancy between retinal and cortical effects is unlikely to be due to the development of "supersensitivity" at the edge of the cortical lesions. An explanation is proposed in terms of lateral spread of information at retinal and/or geniculate stages of the visual system.

Rabbit Visual Cortex: Reaction of Cells to Movement and Contrast

Abstract: IT has been shown that, in the rabbit, retinal ganglion cells1, geniculate cells2,3 and midbrain cells4 respond most readily to special aspects of light stimulation related to movement. In the cat5–7, by contrast, these peripheral systems respond most effectively to an alteration of intensity of a stationary light spot, and have their receptive fields concentrically arranged with “on-centres and off-surrounds” (or vice versa). In the rabbit, on the other hand, the shape and organization of peripheral receptive fields are less stereotyped.