“Compression” of Retinal Responsivity: V-log I Functions and Increment Thresholds

Williams, Theodore P.; Gale, John G.

doi:10.1016/b978-0-12-062260-3.50017-4

Cited by 3 publications

(2 citation statements)

References 15 publications

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“…3A and B have indicated, the interpretation of increment threshold data for large fractional bleaches (B greater than -0.87) is less clear. Interestingly, the relationship of increment threshold functions obtained under such conditions resembles that predicted by certain "response compression" models (Williams and Gale, 1978;Dawis, 1978Dawis, , 1981. Although our data do not establish the involvement of a compression mechanism in the determination of measured threshold, it is apparent that threshold elevations induced by extensive bleaches are accompanied by substantial decreases in Vma~ of the photoreceptor response (of.…”

Section: Bleaching and Increment Thresholdsmentioning

confidence: 42%

Desensitization of skate photoreceptors by bleaching and background light.

Clack¹,

Pepperberg²

1982

The Journal of General Physiology

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Through extracellular measurements of photoreceptor responses to flashed stimuli, we examined how the bleaching of rhodopsin affects increment receptor threshold in the isolated retina of the skate (Raja osceUata and R. erinacea). Both initially unbleached and previously bleached photoreeeptors, when exposed to full-field luminous backgrounds of fixed intensity, attain approximately stable levels of increment threshold that vary with the intensity of the background light. Values of stabilized increment thresholds measured after various extents of bleaching (less than -50%), when plotted against background intensity in log-log coordinates, tend to converge with increasing intensity of the background; this relationship of the increment threshold functions resembles that which Blakemore and Rushton (1965b) found to describe the transient effect of bleaching on psychophysical increment threshold for the human rod mechanism. Our data are consistent with the possibility that related photochemical processes govern the stabilized levels of receptor sensitivity exhibited by the isolated retina (a) during steady illumination and (b) long after substantial bleaching.

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Section: Bleaching and Increment Thresholdsmentioning

confidence: 42%

Desensitization of skate photoreceptors by bleaching and background light.

Clack¹,

Pepperberg²

1982

The Journal of General Physiology

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“…Although other models (i.e. Williams & Gale, 1978;Dawis, 1979) have been proposed to account for transformation from Michaelis-Menten to Weber-Fechner type responses, we have shown a simple relationship for this transition. In this presentation, we do not mean to imply that there may not be other factors to consider besides a change in a which shifts the Michaelis-Menten curve, but simply that such a change determined on the basis of the ratio of plateau to peak alone is sufficient to predict the Michaelis-Menten to WeberFechner sensitivity transformation.…”

Section: Discussionmentioning

confidence: 83%

Sensitivity transformation for vertebrate vision

Chappell

Naka

1991

Vis Neurosci

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The visual response to a flash given in the dark is known to saturate according to the Michaelis-Menten relationship. Nevertheless, the incremental response from increasing levels of mean luminance tends to follow a Weber-Fechner relationship well into the saturation range determined from the Michaelis-Menten results. This sensitivity transformation from Michaelis-Menten to Weber-Fechner is an important characteristic of light adaptation in the vertebrate retina. Recent studies concerning the role of calcium in photoreceptor adaptation have shown that the relaxation from peak to plateau in the response of isolated photoreceptors was absent under conditions in which adaptation was blocked. Comparing the pronounced relaxation from peak to plateau in turtle horizontal cells with the absence of such relaxation in the catfish response, we noted also that turtle incremental sensitivity shows a Weber-Fechner relationship while catfish incremental sensitivity more closely follows the local slope of the Michaelis-Menten relation. Based on these observations, we have obtained an expression to relate the relaxation from peak to plateau with the sensitivity transformation. We assume that adaptation shifts the half-maximum point of the Michaelis-Menten curve so that the light response relaxes to a plateau value equal to a specified fraction of the peak response. We show that this manipulation alone results in a transformation from Michaelis-Menten kinetics to Weber-Fechner sensitivity.

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Action Spectroscopy

Lipson¹

1991

Biophysics of Photoreceptors and Photomovements in Microorganisms

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“Compression” of Retinal Responsivity: V-log I Functions and Increment Thresholds

Cited by 3 publications

References 15 publications

Desensitization of skate photoreceptors by bleaching and background light.

Desensitization of skate photoreceptors by bleaching and background light.

Sensitivity transformation for vertebrate vision

Action Spectroscopy

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