scholarly journals THE NATURE OF FOVEAL DARK ADAPTATION

1921 ◽  
Vol 4 (2) ◽  
pp. 113-139 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Stationary State ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Bimolecular Reaction ◽  
Dark Side ◽  
Light Perception ◽  
Foveal Vision ◽  
Dark Reaction ◽  
Initial Event ◽  
Photosensitive Substance

1. After a discussion of the sources of error involved in the study of dark adaptation, an apparatus and a procedure are described which avoid these errors. The method includes a control of the initial light adaptation, a record of the exact beginning of dark adaptation, and an accurate means of measuring the threshold of the fovea after different intervals in the dark. 2. The results show that dark adaptation of the eye as measured by foveal vision proceeds at a very precipitous rate during the first few seconds, that most of the adaptation takes place during the first 30 seconds, and that the process practically ceases after 10 minutes. These findings explain much of the irregularity of the older data. 3. The changes which correspond to those in the fovea alone are secured by correcting the above results in terms of the movements of the pupil during dark adaptation. 4. On the assumption that the photochemical effect of the light is a linear function of the intensity, it is shown that the dark adaptation of the fovea itself follows the course of a bimolecular reaction. This is interpreted to mean that there are two photolytic products in the fovea; that they are disappearing because they are recombining to form anew the photosensitive substance of the fovea; and that the concentration of these products of photolysis in the sense cell must be increased by a definite fraction in order to produce a visual effect. 5. It is then suggested that the basis of the initial event in foveal light perception is some mechanism that involves a reversible photochemical reaction of which the "dark" reaction is bimolecular. Dark adaptation follows the "dark" reaction; sensory equilibrium is represented by the stationary state; and light adaptation by the shifting of the stationary state to a fresh point of equilibrium toward the "dark" side of the reaction.

scholarly journals DARK ADAPTATION AND THE LIGHT-GROWTH RESPONSE OF PHYCOMYCES

1929 ◽  
Vol 12 (3) ◽  
pp. 391-400 ◽  
Author(s):  
E. S. Castle
Keyword(s):  
Latent Period ◽  
Dark Adaptation ◽  
Growth Response ◽  
Light Adaptation ◽  
Exposure Period ◽  
Bimolecular Reaction ◽  
Dark Reaction ◽  
Action Time ◽  
Kinetics Of ◽  
Photochemical Action

1. A single-celled, elongating sporangiophore of Phycomyces responds to a sufficient increase in intensity of illumination by a brief increase in growth rate. This is the "light-growth response" of Blaauw. 2. The reaction time is compound, consisting of an exposure period and a latent period (this comprising both the true latent period resulting from photochemical action and any "action time" necessary for the response). During the latter period the plant may be in darkness, responding nevertheless at the end of the latent period. 3. Both light adaptation and dark adaptation occur in the sporangiophore. The kinetics of dark adaptation can be accounted for on the basis of a bimolecular reaction, perhaps modified by autocatalysis. Attention is called to the bimolecular nature of the "dark" reaction in all other photosensory systems that have been studied, in spite of the diversity of the photosensitive substances themselves and of the different forms of the responses to light.

scholarly journals SENSORY EQUILIBRIUM AND DARK ADAPTATION IN MYA ARENARIA

1919 ◽  
Vol 1 (5) ◽  
pp. 545-558 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Reaction Time ◽  
Latent Period ◽  
Dark Adaptation ◽  
Photochemical Reaction ◽  
Short Interval ◽  
Bimolecular Reaction ◽  
Mya Arenaria ◽  
Rational Explanation ◽  
Order Of Magnitude ◽  
Photosensitive Substance

1. The reaction time of Mya to light is composed of two parts. The first, a sensitization period, is an exceedingly short interval of the order of magnitude associated with photographic processes. The second is a latent period of about 1.3 seconds, during which Mya need not remain exposed to the stimulating light. 2. The process of dark adaptation in Mya is orderly. Its progress may be represented by the formation of a photosensitive substance according to the dynamics of a bimolecular reaction. See PDF for Structure 3. Photosensory equilibrium as represented by the light- and dark-adapted conditions finds a rational explanation in terms of the "stationary state" of a reversible photochemical reaction involving a photosensitive substance and its two precursors. 4. There are two corollaries to this hypothesis. The first requires that the reaction time at sensory equilibrium for a given intensity should vary inversely with the temperature; the second, that the rate of dark adaptation should vary directly with the temperature. Experiments verified both of these requirements.

scholarly journals THE DARK ADAPTATION OF THE HUMAN EYE

1920 ◽  
Vol 2 (5) ◽  
pp. 499-517 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Dark Adaptation ◽  
Photochemical Reaction ◽  
Quantitative Data ◽  
Dark Reaction ◽  
Human Eye ◽  
Visual Threshold ◽  
Bimolecular Chemical Reaction ◽  
Dim Light ◽  
Visual Reception ◽  
Photosensitive Substance

During the dark adaptation of the human eye, its visual threshold decreases to a small fraction of its original value in the light. An analysis of the quantitative data describing this adaptation shows that it follows the course of a bimolecular chemical reaction. On the basis of these findings it is suggested that visual reception in dim light is conditioned by a reversible photochemical reaction involving a photosensitive substance and its two products of decomposition. Accordingly, dark adaptation depends on the course of the "dark" reaction during which the two products of decomposition reunite to synthesize the original photosensitive substance.

The Cockroach DCMD Neurone: I. Lateral Inhibition and the Effects of Light- and Dark-adaptation

1982 ◽  
Vol 99 (1) ◽  
pp. 61-90 ◽  
Author(s):  
DONALD H. EDWARDS
Keyword(s):  
Lateral Inhibition ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Absolute Intensity ◽  
Recurrent Network ◽  
Light Spot ◽  
Movement Detector ◽  
Threshold Response ◽  
Inhibitory Network ◽  
Local Background

1. The responses of the cockroach descending contralateral movement detector (DCMD) neurone to moving light stimuli were studied under both light- and dark-adapted conditions. 2. With light-adaptation the response of the DCMD to two moving 2° (diam.) spots of white light is less than the response to a single spot when the two spots are separated by less than 10° (Fig. 2). 3. With light-adaptation the response of the DCMD to a single moving light spot is a sigmoidally shaped function of the logarithm of the light intensity (Fig. 3a). With dark-adaptation the response of a DCMD to a single moving light spot is a bell-shaped function of the logarithm of the stimulus intensity (Fig. 3b). The absolute intensity that evokes a threshold response is about one-and-a-half log units less in the dark-adapted eye than in the light-adapted eye. 4. The decrease in the DCMD's response that occurs when two stimuli are closer than 10°, and when a single bright stimulus is made brighter, indicates that lateral inhibition operates among the afferents to the DCMD. 5. It is shown that this inhibition cannot be produced by a recurrent lateral inhibitory network. A model of the afferent path that contains a non-recurrent lateral inhibitory network can account for the response/intensity plots of the DCMD recorded under both light-adapted and dark-adapted conditions. 6. The threshold intensity of the DCMD is increased if a stationary pattern of light is present near the path of the moving spot stimulus. This is shown to be due to a peripheral tonic lateral inhibition that is distinct from the non-recurrent lateral inhibition described earlier. 7. It is suggested that the peripheral lateral inhibition acts to adjust the threshold of afferents to local background light levels, while the proximal non-recurrent network acts to enhance the acuity of the eye to small objects in the visual field, and to filter out whole-field stimuli.

scholarly journals Separation of the ‘blue’ and ‘green’ mechanisms of foveal vision by measurements of increment thresholds

1946 ◽  
Vol 133 (873) ◽  
pp. 418-434 ◽  
Keyword(s):  
Test Stimulus ◽  
High Intensity ◽  
Light Adaptation ◽  
Foveal Vision ◽  
Low Intensity ◽  
Individual Variations ◽  
Low Threshold ◽  
Intense Light ◽  
The Individual ◽  
Very High

The curve relating the smallest perceptible intensity of a blue test stimulus with the intensity of an orange conditioning field against which it is viewed shows a characteristic division into low- and high-intensity components, indicating the operation of two mechanisms of cone vision at the fovea. The justification for calling these ‘blue’ and ‘green’ mechanisms is taken from an earlier investigation (Stiles 1939). While most subjects show this division clearly, for some the low-intensity component is masked by the intrusion of rod vision. The correctness of this view is established by measurements made while the eye is recovering from an intense light adaptation. The individual variations of the sensitivities of the ‘green’ and ‘blue’ mechanisms in twenty subjects are assessed. Further evidence is obtained of an anomalously low threshold for the ‘blue’ mechanisms at very high conditioning fields of orange light.

The Effect of Changed Extracellular Calcium and Sodium Concentration on the Electroretinogram of the Crayfish Retina

1980 ◽  
Vol 35 (3-4) ◽  
pp. 308-318 ◽  
Author(s):  
H. Stieve ◽  
I. Claßen-Linke
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Calcium Concentration ◽  
Light Adaptation ◽  
Sodium Concentration ◽  
Strong Increase ◽  
Calcium Stores ◽  
Half Time ◽  
Astacus Leptodactylus ◽  
External Calcium

Abstract The electroretinogram (ERG) of the isolated retina of the crayfish Astacus leptodactylus evoked by strong 10 ms light flashes at constant 5 min intervals was measured while the retina was continuously superfused with various salines which differed in Ca2+ -and Na+ -concentrations. The osmotic pressure of test- and reference-saline was adjusted to be identical by adding sucrose. Results: 1. Upon raising the calcium-concentration of the superfusate in the range of 20-150 mmol/l (constant Na+ -concentration: 208 mmol/l) the peak amplitude hmax and the half time of decay t2 of the ERG both decrease gradually up to about 50% in respect to the corresponding value in reference saline. 2. The recovery of the ERG due to dark adaptation following the “weakly light adapted state” is greatly diminished in high external [Ca2+]ex. 3. Lowering the external calcium-concentration (10 →1 mmol/l) causes a small increase in hmax and a strong increase of the half time of decay t2 (about 180%). Upon lowering the calcium concentration of the superfusate to about 1 nmol/l by 1 mmol/l of the calcium buffer EDTA, a slowly augmenting diminution of the ERG height hm SLX occurs. How­ever, a strong retardation of the falling phase of the ERG characterized by an increase in t2 occurs quickly. Even after 90 min stay in the low calcium saline the retina is still not inexcitable; hmax is 5 - 10% of the reference value. The diminution of hmax occurs about six-fold faster when the buffer concentration is raised to 10 mmol/l EDTA. 4. Additional lowering of the Na+ -concentration (208 →20.8 mmol/l) in a superfusate with a calcium concentration raised to 150 mmol/l causes a strong reduction of the ERG amplitude hmax to about 10%. 5. In a superfusate containing 1 nmol/l calcium such lowering of the sodium concentration (208 → 20.8 mmol/l) causes a diminution of the ERG height to about 40% and the shape of the ERG to become polyphasic; at least two maxima with different time to peak values are observed. Interpretation: 1. The similarity of effects, namely raising external calcium concentration and light adaptation on the one hand and lowering external calcium and dark adaptation on the other hand may indicate that the external calcium is acting on the adaptation mechanism of the photoreceptor cells, presumably by influencing the intracellular [Ca2+]. 2. The great tolerance of the retina against Ca2+ -deficiency in the superfusate might be effected by calcium stores in the retina which need high Ca2+ -buffer concentrations in the superfusate to become exhausted. 3. In contrast to the Limulus ventral nerve photoreceptor there does not seem to be an antagonis­ tic effect of sodium and calcium in the crayfish retina on the control of the light channels. 4. The crayfish receptor potential seems to be composed of at least two different processes. Lowering calcium-and lowering external sodium-concentration both diminish the height and change the time course of the two components to a different degree. This could be caused by in­ fluencing the state of adaptation and thereby making the two maxima separately visible.

Changes of Acuity during Light and Dark Adaptation in the Dragonfly Compound Eye

1990 ◽  
Vol 45 (1-2) ◽  
pp. 137-142 ◽  
Author(s):  
Eric J. Warrant ◽  
Robert B. Pinter
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Light Adaptation ◽  
Compound Eye ◽  
Sensitivity Function ◽  
The State ◽  
Intracellular Recordings ◽  
Acceptance Angle ◽  
Angular Sensitivity ◽  
Rapid Reduction

Abstract Intracellular recordings of angular sensitivity from the photoreceptors of Aeschnid dragonflies (Hemianax papuensis and Aeschna brevistyla) are used to determine the magnitude and time course of acuity changes following alterations of the state of light or dark adaptation. Acuity is defined on the basis of the acceptance angle, Δρ (the half-width of the angular-sensitivity function). The maximally light-adapted value of Δρ is half the dark-adapted value, indicating greater acuity during light adaptation. Following a change from light to dark adaptation, Δρ increases slowly, requiring at least 3 min to reach its dark-adapted value. In contrast, the reverse change (dark to light) induces a rapid reduction of Δρ , and at maximal adapting luminances, this reduction takes place in less than 10 sec.

Effect of amobarbital on the course of human dark adaptation

1961 ◽  
Vol 16 (2) ◽  
pp. 361-366 ◽  
Author(s):  
G. W. Granger
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Oral Administration ◽  
White Light ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Visual Adaptation ◽  
Test Field ◽  
The Central Nervous System ◽  
The Stability

Following light adaptation to a luminance of 120 mL for 5 minutes, absolute thresholds for a centrally fixated, 7-degree test field in 'white' light were measured during the course of 30 minutes' dark adaptation. Viewing was monocular and the measuring light was exposed in 0.018-second flashes. The resulting curves, defining the relation between log threshold luminance and time in the dark, displayed the typical features of 'rod' dark adaptation and were found to be highly reproducible in three experienced observers. Neither the shape of the curves nor their position along the log luminance axis was affected by the oral administration of a sedative dose (0.30 gm/70 kg) of amobarbital. It was concluded that the results supported the views of Hecht and other photochemical theorists concerning the stability of human dark adaptation and its resistance to fluctuations in the state of the central nervous system, but were not necessarily incompatible, as was sometimes supposed, with the hypothesis of a neural component in visual adaptation. Submitted on May 23, 1960

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