Abstract
1 The retina is a thin sheet of neural tissue that partially lines the orb of the eye. This tiny outpost of the central nervous system is responsible for collecting all the visual information that reaches the brain. Signals from the retina must carry reliable information about properties of objects in the world over many orders of magnitude of illumination. Furthermore, these signals are generated by transducers whose characteristics are innately mismatched and must be continuously self-calibrated. Some of the mechanisms by which the retina achieves this feat are embodied in a two-dimensional CMOS chip, the silicon retina.
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Notes
Portions of this chapter have been reproduced from Chapter 15 of Analog VLSI and Neural Systems [65] with the permission of Addison-Wesley.
The differences among various retinae are beyond the scope of this text. Peter Sterling has written a concise summary of the vertebrate retina in Gordon Shepherd&$#x2019s book, The Synaptic Organization of the Brain [102]. John Dowling has written a wonderful book, The Retina: An Approachable Part of the Brain [24], that organizes the information that has been gathered about retinae from diverse vertebrate species.
Lateral inhibition is a ubiquitous feature of peripheral sensory systems [106]. A summary of mathematical analysis of feedforward andrecurrent models of lateral inhibition is given in Ratliff [89]. These models are not hardware oriented, and have focused mainly on mathematically specified input-output, relationships without concern for the mechanisms by which these relations are achieved.
Shapley and Enroth-Cugell have written a comprehensive explanation of retinal adaptation and of the role or adaptation in illuminant-invariant perception [94].
Unlike the feedforward model, the feedback model predicts that the sustained response of the photoreceptors to a large diameter test flash should be smaller than the sustained response of the photoreceptors to a small diameter test flash.
See Shapley et al. [94] for a review of the application of the Naka—Rushton relation to photoreceptor responses. Also, see Boahan [8] for a silicon implementation of this mechanism.
See Grossberg [29] for a mathematical analysis of shunting networks that support perceptual invariance.
See Pugh and Lamb [88] for a review of calcium-mediated receptor adaptation.
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© 1994 Springer Science+Business Media New York
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Mahowald, M. (1994). The Silicon Retina. In: An Analog VLSI System for Stereoscopic Vision. The Springer International Series in Engineering and Computer Science, vol 265. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-2724-4_2
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DOI: https://doi.org/10.1007/978-1-4615-2724-4_2
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