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VISUAL PERCEPTION

It is a complex integration of light sense, form sense, sense of contrast and colour sense. The receptive field organization of the retina and cortex are used to encode this information about a visual image.

1. The light sense
It is awareness of the light. The minimum brightness required to evoke a sensation of light is called the light minimum. It should be measured when the eye is dark adapted for at least 20-30 minutes. The human eye in its ordinary use throughout the day is capable of functioning normally over an exceedingly wide range of illumination by a

Continue vision physiology (1)

PROCESSING AND TRANSMISSION OF VISUAL
IMPULSE
The receptor potential generated in the photoreceptors is transmitted by electrotonic
conduction (i.e., direct flow of electric current, and not as action potential) to other cells of the retina viz. horizontal cells, amacrine cells, and ganglion cells. However, the ganglion cells transmit the visual signals by means of action potential to the neurons of lateral geniculate body and the later to the primary visual cortex. The phenomenon of processing of visual impulse is very complicated. It is now clear that visual image is deciphered and analyzed in both serial and parallel fashion. Serial processing. The successive cells in the visual pathway starting from the photoreceptors to the