Information processing, retina

The rod and cone cells found in the retina of the eye are functional supramolecular devices involved in information processing. Rod cells function in dim light and are black and white receptors while cones are colour receptors. 

Dowhng, JE (1979) Information processing by local circuits The vertebrate retina a model system. In F.O. Schmitt and F.G. Worden (eds) The Neurosciences Fourth Study Program. Cambridge, MA MIT Press. 

Mahowald, M.A. Silicon Retina with Adaptive Photoreceptors, in Visual Information Processing From Neurons to Chips. 1991. Orlando, FL SPIE. 

The sensory organ of the HVS (Human Visual System) is the retina, a photosensitive layer on the backside of the eye. However, the formation of highly detailed mental representations of the perceived scene not only demands the capture of light information but a complex information processing-chain with multiple layers of... 

The majority of the volume of the eye consists of the vitreous chamber, which is filled with the vitreous humor, a transparent, gelatinous mass of extracellular matrix material similar to the comeal stroma which is expressed during development. The vitreous humor holds the neural layer of the eye—the retina—in position. The retina is comprised of 10 layers of nervous tissue made up of millions of hierarchically organized light receptors that are connected to the brain by the optic nerve. The neural layer is not believed to exhibit specific responses to most agents, except in the cases where systemic distribution of neurotoxic CWAs may have a pathophysiological effect on retinal function and information processing. 

Figure 2.9 Path from the retina to the visual cortex. On its way to the lateral geniculate nucleus, some axons cross at the optic chiasm. Information from the right half of the visual field is processed inside the left hemisphere of the brain. Information from the left half of the visual field is processed inside the right hemisphere. (Reproduced from Semir Zeki. A Vision of the Brain. Blackwell Science, Oxford, 1993, by permission of Blackwell Science, UK.)...

A consortium of 13 technical and medical partners works on different tasks to develop a complete system for a visual prosthesis (Fig. 25). The neural pros-theses comprises a unit to record and process ambiance light, an encoder that transforms visual information into a sequence of stimulation pulses, a micro-electromechanical system that is implanted into the eye for interfacing the retina and for generating the appropriate stimuli. 

The main difference of our project is the development of a retina encoder which simulates the signal processing of the different layers of the retina. The encoder transforms visual information into stimuli for the ganglion cells. The stimulation patterns should resemble the ones obtained from a non damaged retina. In detail, a high speed, pixel addressable camera with a light sensitivity of... 

It now appears that nearly, if not all, chordates are tetrachromatic in retinal capability and it would be very strange if this capability was not used to process chrominance as well as luminance information. It is also clear that the human retina is tetrachromatic and that the human processes all of the available information (in spite of a blockage of irradiation at wavelengths shorter than 400 nm by the lens). 

In addidon to transducing the incoming light, the retina plays a number of important roles in the initial process of analyzing visual information. In the following section, we consider the retinal circuitry employed for analysis of edges, color, directional selectivity, and scotopic vision. 

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