Rods, Cones, and the Chemical Basis of Vision

Hecht, Selig

doi:10.1152/physrev.1937.17.2.239

Cited by 277 publications

(83 citation statements)

References 59 publications

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“…Hence the latter is directly proportional to a. Recently Hecht (1937) has pointed out that ot is related to ¢, the absorption coefficient ( = 2.303 × extinction) by an expansion of the form, ot = ~ -~. q-~.…”

Section: Discussionmentioning

confidence: 99%

On Rhodopsin in Solution

Wald

1938

Journal of General Physiology

124

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1. The properties of rhodopsin in solution have been examined in preparations from marine fishes, frogs, and mammals. 2. The bleaching of neutral rhodopsin in solution includes a photic and at least three thermal ("dark") processes. Thermal reactions account for approximately half the total fall in extinction at 500 mµ. 3. Bleaching has been investigated at various pH's from 3.9 to about 11. With increase in pH the velocity of the thermal components increases rapidly. Though the spectrum of rhodopsin itself is scarcely affected by change in pH, the spectra of all product-mixtures following irradiation are highly pH-labile. 4. The spectrum of pure rhodopsin—or of the rhodopsin chromophore—is fixed within narrow limits. The extinction at 400 mµ lies between 0.20 to 0.32 of that at the maximum. 5. Within the limitations of available data, the spectrum of pure rhodopsin corresponds in form and position with the spectral sensitivity of human rod vision, computed at the retinal surface. 6. The nature of bleaching of rhodopsin in solution, its kinetics, and its significance in the retinal cycle are discussed.

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Section: Discussionmentioning

confidence: 99%

On Rhodopsin in Solution

Wald

1938

Journal of General Physiology

124

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“…As a result, one obtains discontinuous dark-adaptation curves with two sectors, each reflecting one o f t he receptor activities, from organisms whose retinas possess both systems. Such a eurve was demonstrated long ago in humans (Kohlrausch, 1922;Hecht, 1937). The general aim of the present study was to obtain dark adaptation data for the American red squirrel, using a psyehophysical tracking proeedure, and to see if evidenee for duplex function could be found.…”

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confidence: 78%

A behavioral measure of dark adaptation in the American red squirrel

Dippner

Armington

1971

Psychon Sci

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A behavioral tracking technique was used to investigate dark adaptation in two American red squirrels (Tamiosciurus hudsonicus). Increase of sensitivity was followed over a range of about 4 log units. A break typical of duplex retinas appeared in the dark-adaptation curve about 18 min after the beginning of adaptation. More than 30 min was required for complete adaptation, with the final threshold of the squirrel about 1.5 log units above that of the human measured on the same apparatus.According to duplicity theory, the visual systems of some species are made up of two such systems, which take their origin with two types oe receptors, the rods and the cones. The rod and cone systems in duplex retinas typically mediate vision at different levels of illumination. Both systems increase their sensitivity in darkness, but not to the same degree. The cone system adapts more rapidly and over a smaller range than does the rod system. As a result, one obtains discontinuous dark-adaptation curves with two sectors, each reflecting one o f t he receptor activities, from organisms whose retinas possess both systems.

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“…The rods and the cones possess different sensibility distributions in the spectrum, and this has been used to separate the two systems in measurements of dark adaptation (Kohlrausch, 1931), intermittent stimulation (Hecht and Shlaer, 1936), visual acuity (Koenig, 1897;Hecht, 1937a), and instantaneous threshold (Blanchard, 1918;Hecht, 1937 b). For intensity discrimination this would mean that in measurements made with extreme red light, the relationship between A[[I and [ would be a single high intensity function even when the field is large; while with other parts of the spectrum more and more of the low intensity section should appear as the wavelength of the light moves toward the blue.…”

Section: IImentioning

confidence: 99%

Intensity Discrimination in the Human Eye

Hecht

Peskin

Patt

1938

Journal of General Physiology

Self Cite

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I Purpose of This ResearchWhen I and [ + AI are two light intensities which can just barely be recognized as different, then the fraction AI/I is considered the measure of intensity discrimination. The value of this fraction and its relation to the intensity f have been the subject of many researches, and these have established that as the intensity Z increases, the fraction A[/I decreases, tending toward a minimum value at the highest intensities. This is true not only for the human eye, but for all other organisms thus far studied, namely, Drosophila, the bee, and Mya (for a summary, see Hecht, 1937 a).Besides the general relation of A[/I to I, the human eye shows an additional phenomenon due to the duality of its retinal structure.There seem to be two relations of A[/I to I, one at the lower intensities representing rod function, and the other at high intensities representing cone function. This rod-cone dichotomy is apparent in nearly all the published measurements from the earliest by Aubert (1865) to the most recent of Steinhardt (1936). In addition, Steinhardt showed that the double function appears only in measurements with central visual fields larger than 2 ° , while the single function appears with fields smaller than 2 ° , and this corresponds to the presence of rods and cones in the larger fields, and to the complete absence of rods in the smaller fields. Moreover, the extent of the low intensity rod section increases with the size of the field because of the increasing number of rods present in comparison with the number of cones.

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Rods, Cones, and the Chemical Basis of Vision

Cited by 277 publications

References 59 publications

On Rhodopsin in Solution

On Rhodopsin in Solution

A behavioral measure of dark adaptation in the American red squirrel

Intensity Discrimination in the Human Eye

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