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Abstract:
I will discuss the amount of visual input information along the visual pathway from retinal inputs, to retinal outputs, to visual perception. In humans, there are about one megabytes per second (compressed from about 20 MB/second of raw visual inputs) of visual input information being transmitted in the optic nerve from the retina. One megabytes can contain the amount of information in the text in a large book. It has been measured, since 1950s, that only about 40 bits per second of information is admitted to the attentional bottleneck, due to the limited processing power in the brain (40 bits contains roughly the amount of information in two short sentences of text). This bottleneck is manifested in the inattentional blindness behaviorally. An important question is, where along the visual pathway, from the optic nerve to the perceptual outcome and awareness, is the information being lost. I will argue that, to a substantial extent, the bottleneck starts around the output of the primary visual cortex (V1). This is partly suggested by the recent evidence supporting the V1 Saliency Hypothesis (V1SH) that the attentional selection of visual inputs, by gaze shifts, is partly guided exogenenously by a bottom-up saliency map created by V1. Secondly, it is apparent that much of the information available in V1 is not available in visual perception, or not even in V2, the extrastriate cortex immediately downstream from V1 along the visual pathway. For example, the information about the eye of origin of visual inputs is lost by V2, whose neurons are mostly binocular and thus blind to the eye of origin of visual inputs. Recognizing this bottleneck starting at V1's output suggests a new framework to understand vision.
