Smulation Study Of Information Parallel Prcessin In The Bionic Retina

The retina, also known as peripheral brain is part of the brain. It is a very thin layer of neural structure which use for efficiently extract and code outside scenery information, and send different scenery information by nerve impulses to visual cortex in parallel. The retina constitutes by five kinds of cells which are photoreceptor cell, horizontal cell, bipolar cell, amacrine cell and ganglion cell. Photoreceptor cell is a photoelectric transducer that transform illumination signal into nerve signal. Horizontal cells and amacrine cells respectively provided surround signals to bipolar cells and ganglion cells which have center-surround antagonism receptive field. The bipolar cells use in extracting different outside scenery information separately. The ganglion cells calculate the information form center-surround antagonism receptive field, and send the final result to visual cortex in parallel.In the retina the visual information is processed in parallel. In this paper has designed four parallel visual processing circuits which are color circuit, luminance circuit, subdued light circuit and movement circuit. The color circuit mainly constitute by midget neuron which'density is highest in the foveal pit. This circuit function is extracting high resolution color information which are red,green and blue information.In the ganglion cells layer,the midget ganglion cells extract color information by red-green antagonism and blue-yellow antagonism.The center surround antagonism value is 1:1. The luminance circuit is constitute by parasol neuron which' density is low in the retina. This circuit function is extracting low resolution luminance information. In the same way the parasol ganglion cells extract luminance by center surround antagonism, and the value is 1:0.25. The subdued light circuit is constitute by rod neuron, and operate in dim condition. The rod system has the very high sensitivity to the luminance.The rod bipolar cells do not have center surround antagonism receptive field,and receive dim light information from its wide field dendrite.Because the retina does not have ganglion cells for rod system to transfer signals,the rod system use All amacrine cells make gap junctions with the axons of diffuse bipolar cells which in turn synapses with on ganglion cells.So rod system with the help of luminance circuit to send signal to senior visual cortex. The movement circuit extracts the movement information from diffuse bipolar cells which deliver luminance and subdued light signal.The DS ganglion cells receive excitatory signal from diffuse bipolar which are located within its dendrite,and receive inhibitory signal from starburst amacrine which are point in the ganglion cell's null direction.So excitatory signal and inhibitory signal are offset spatially and temporally.This is the essential reason why DS ganglion can detect movement.In this paper DS ganglion cell comprises four subtypes which prefer one of four directions.We have constructed the software retina system according to the retina process visual information in parallel,and has conducted experimental study to its mechanism .①we conduct simulator study on scenery's static information extraction,pointed out that the retina extract four kinds of visual information and deliver them in parallel.At the same time we confirmed the center surround antagonism in the ganglion cells .②we conduct simulator study on electrical coupling between photoreceptors,and find out that the coupling between photoreceptors improves the signal-to-noise ratio by shielding the noise which was created in phototransformation .③we conduct simulator study on midget bipolar's center surround antagonism,pointed out that the surround receive color or luminance signals has little effect on the output of midget bipolar cell. The influence coefficient is 5.15%.④we conduct simulator study on extracting movement information from scenery. In trials we extract movement information in four direction respectively, and the test result indicates DS ganglion cell which receive signals offset spatially and temporally can effectively discriminate the movement. Eventually,the retina send four kinds of movement information to visual cortex in parallel.