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We have presented evidence that local retinal adaptation is not the cause of spatial frequency channels. This was done by minimizing local retinal adaptation with gratings whose contrast was a sinusoidal function of time. The gratings were viewed through an image stabilization apparatus to ensure that the subject would not fixate preferentially on certain portions of the grating providing uneven retinal adaptation.

We recorded by intracellular means responses of horizontal cells of the turtle retina to light increase and decrease of different values against the starting adapting level. In measuring these responses, curves reflecting the dependence of membrane potential deflection on light intensity (amplitude characteristics — ACh) were plotted. It is demonstrated that the ACh of transitional processes (on- and off-peaks) is considerably steeper than ACh of the plateau of the potential, but embraces a much smaller range of light intensities (slightly more than 1 log. un.). During a change in intensity of the adapting background (up to 3 log. un.), the ACh of transitional processes shifts along the scale of light intensities in such a way that its steep part remains in the zone of adapting light. We followed the dynamics in time of ACh shift after the transition from one adapting brightness to another. The ACh of total impulse response was plotted for ganglionic cells of the turtle at different intensities of adapting light. Comparison of these curves with the ACh of horizontal cells shows that its peripheral components are responsible for adaptive shifts of ACh of the visual system and that horizontal cells play an important role in the mechanism of adaptation. It is hypothesized that adaptive ACh shifts are the consequence of positive feedback between the horizontal cells and receptors.

The electrical threshold of the eye was measured by the alternating current of 20 c. p. s. with flicker sensation caused by it as an index under various adaptation states. 1. The threshold-time curve during complete dark adaptation following light adaptation of 10 minutes to illumination of 9, 800 lux shows the following course: At first the threshold remained low for about 8 minutes, and then increased rapidly to attain a constant level in about 15 minutes. Thus, the curve showed an inflection at about 8 minutes. 2. The curve suffered from a modification when the retina was constantly exposed to a small point of light of 40' in visual angle following the same light adaptation as above. The inflection at the middle stage became more obscure and the final level lower as local illumination was moved farther towards the periphery of the retina. 3. The effect of similar local illumination was investigated with colored lights. When blue, green and red lights were used for local illumination, it was found that the red light showed an effect similar to white light confined to the fovea, but that the green and blue light acted as white light illuminating the periphery of the retina. 4. Next the effect of exposure to broad illumination was investigated upon the curve following the same light adaptation as above. The curves by illumination of 0.1 lux, 1 lux and 10 lux were low and almost steady, but those by 100 and 1, 000 lux were generally much higher. From these experiments it is likely that the threshold as determined by the A. C. of 20 c. p. s. is lowered when visual cells, especially rods are excited to some extent.

Retinal adaptation to prism-displaced hand image in terms of sensorimotor coordination central control change

Correction factors required for estimating influence of pupil area reduction on retinal illumination at oblique angles

“Empfindungszeit” (“E. Z.”) for a wide range from the center to the periphery of the retina was measured by a modified Hazelhoff's method under various states of adaptation. (1) It was proved that our method satisfied the necessary conditions for measuring the “E. Z.” that an observer could make his gaze follow a fixation point travelling at a constant speed. (2) The speed of the eye movement has no influence on the “E. Z.” within the range of the speed from 10° to 44° per sec. in visual angle in the horizontal direction. (3) At a constant intensity of a light stimulus, light adaptation causes an elongation of the “E. Z.”, and the ratio of the “E. Z.'s” determined predominantly by the cone function at two different retinal parts remains constant irrespective of adaptation. (4) Under dark adaptation, the value of the “E. Z.” at a high in-tensity of the stimulus shows two minima at the fovea and about 30° peri-phery and two maxima at about 10° parafovea and the extreme periphery, while the value of the “E. Z.” at a low intensity of the stimulus shows only a minimum at about 30° periphery. (5) The question whether cones or rods predominate for the “E. Z.” seems to depend on the ratio of the densities of rods and cones of the retinal area stimulated. The shortest “E. Z.'s” determined by the cone function and by the rod function are obtained at the fovea and at about 30° peri-phery respectively, and the former is shorter than the latter. We wish to thank Prof. K. Motokawa for his advice and helpfulness.

Hear, white noise, and flicker increased the rate of reversals of the Necker cube. Luminosity of lines, background illumination, and retinal adaptation failed to influence reversal rate. These results are discussed in relation to the concept of activation and the theory of satiation of orientation.

1. Spike responses of single optic tectal units to plane polarized light have been recorded with extracellular electrodes in the goldfish. Responses to a series of eight 500 msec flashes were summed and the quantitative effects ofe-vector direction studied over 4–5 log units of intensity with white light and narrow spectral bands of equal quantal content at 460, 540 and 620 nm. 2. As previously reported all or nearly all tectal cells tested (115) were sensitive to the direction of the stimulus' polarization plane. Control experiments with a thin high order birefringent retarder next to the cornea and acting as a pseudo depolarizer provided further proof that thee-vector discrimination found in the optic tectum (as well as the previously reported oriented behavior to polarized light in fish) depends on an intraocular analyzer. 3. Systematic study of tectal cells has been made at various depths and in all directly accessible areas. No localized or differential effects of recording depth one-vector discrimination have been found. However, both directions of maximum response and degree of polarized light sensitivity (PLS) show distinctive patterns over the tectal area. 4. On the basis of established tectal projection maps these data show that preferred retinale-vector directions are tangentially arranged around the eye axis when the stimulus is axial. Distribution of this angular sensitivity seems continuous without discrete channels favoring particular polarization planes. 5. Sensitivity (determined from intensity response curves) is minimal in the center of the retina for an axial stimulus and increases peripherally out to 50–60° or more off axis. Sensitivity ratios of 4–6 are common and much larger ones have been occasionally recorded. 6. Shifting the direction of stimulus from axial to 45° and 60° upward from the axis proved that retinal patterns of preferrede-vector directions and sensitivities are symmetrical relative to the beam axis rather than the anatomical eye axis. Therefore individual tectal cells and before them their retinal receptor elements show different directions ofe-vector preference and different PLS ratios depending on the stimulus configuration. 7. Intensity response curves determined with the red, green and blue narrow spectral bands were essentially superimposable. Therefore, we have no evidence that there is any special interaction of λ and PLS. 8. The effects of stimulus intensity and retinal adaptation on the IR curves do not indicate any particular selective effects. Substantial polarized light sensitivity was present in both the light adapted and dark adapted state. PLS ratios in various cases were (1) about the same at different intensity levels or (2) greater at low than high intensities or (3) greater at high than low intensities. 9. We conclude that linearly polarized light evokes a large entoptic image in the goldfish eye. Two opposite light sectors perpendicular to thee-vector alternate with two dark sectors parallel to thee-vector. Both Haidinger's brushes and Boehm's brushes in human vision show some similarities but also some important differences. The goldfish PL image is achromatic, weak or absent axially and strong peripherally. Also the contrast between the sectors does not depend on movement of the stimulus on the retina to prevent fading as it does in both of the other phenomena. 10. The most likely mechanism for the observed PLS in the goldfish eye is either differential scattering intraocularly or oblique entry of light into the receptor outer segments. Yet present data prevent a firm choice between them.

Changes in the electroretinogram (ERG) are studied in patients with large chorioretinal scars and certain hereditary retinal diseases. Amplitude and implicit time of the ERG responses are shown to behave independently of one another in these conditions. Chorioretinal destruction produces a reduction in amplitude but no change in implicit time. Hereditary disease leads to reduction in amplitude which can be accompanied by changes in implicit time. Some degenerations produce changes in implicit time before changes in amplitude. The delays in implicit time can be best explained by an abnormality of the rod and/or cone receptor system involving the entire retina. Alterations of implicit time due to the intensity and area of light stimulation and the state of retinal adaptation are considered.

Retinae of fish exposed to 9 × 102 ft-c are more fully adapted to light than those of fish exposed to 10−1 ft-c. Retinae of the former group take a shorter time to attain the same state of adaptation as that of the latter. However, they take a longer time than the latter to attain their own maximum state of adaptation. Retinae of fish subjected to darkness after exposure to 9 × 102 ft-c are not dark-adapted even after 70 minutes. The retinal epithelial pigment of fishes placed in darkness from light of 10−1 ft-c dark-adapts in 45 minutes while the cones do so in 25 minutes. The retinal index indicates that dark-adaptation occurs 45 minutes after subjection to dark. Hypotheses presented in a previous paper are discussed in the light of these results.

An image which is stabilised with respect to the retina functionally eliminates the micronystagmoid movements of the eyeball. The degree of elimination depends on the accuracy of stabilisation achieved. A variety of apparatus has been used to try and achieve accurate stabilisation but at the same time to provide a method which permits the use of a wide range of material to act as the stabilised target. The stabilised image has been studied with various types of images and under various conditions of viewing. The fading of the stabilised image is comparable with Troxler's Effect. The comparative study of these two phenomena leads to some interesting conclusions. An attempt has been made to relate the fading of the stabilised image to Troxler's Effect and to understand the fading process in terms of retinal adaptation, eye movements, and the part played by higher centres in the visual pathway. As well as throwing light on the function of the eye movements, the study of the stabilised retinal image has been used in the field of psychology to investigate figural after-effects, geometrical illusions, and theories of perception.

Prismatic adaptation under scotopic and photopic conditions in subjects, using transfer experiments

The retinal threshold was measured along the horizontal meridian for the dark-adapted eye and for the same retinal region light-adapted by stray light from a small foveally fixated high-luminance target. This was done to quantify the irradiation phenomenon in the foveal-parafoveal boundary region. Two target luminances were investigated (5,531 and 13,000 fL). Seven Ss made threshold settings using a variable-intensity test spot whose retinal image was located at various angular separations from the foveal center as far as 10 deg in the temporal field. Threshold slopes were steeper for test spots imaged from 15min to 1 deg of arc from the foveal center than for spots imaged from ldegl5min to 10 deg of arc from the foveal center for the illuminated target conditions. The angular distance between the fovea and the intersection of the steep component with the shallow component of each threshold curve tended to shift toward the target’s edge with an increase in target luminance. These data are interpreted as an indication that a dynamic neural mechanism is involved in producing the irradiation phenomenon.

Perceptual masking was studied under binocular and dichoptic conditions in order to separate peripheral and central interference effects. Under binocular conditions, when the test flash (TF) and the blanking flash (BF) fell on both retinas, both retroactive and proactive masking were demonstrated. Under dichoptic conditions, when the TF fell on one eye and the BF on the other eye, thus eliminating opportunity for intraretinal interference, there was partial retroactive perceptual masking and no proactive masking. These results suggest that binocular proactive masking is due to peripheral light adaptation, that binocular retroactive masking is due to both peripheral and central effects, and that dichoptic masking is due solely to central retrochiasmal interference. It is proposed that dichoptic retroactive perceptual masking affords a method of investigating central perception time, i.e., the time to consolidate a perceptual experience.

It was shown that natural illumination determines retinal adaptation. The moment of special onterest occurred at the change from daylight to twilight whsion while the person under observation was in natural conditions. Measurement of the retinal light sensitivity showed that the change from daylight to twilight vision was brought about by an increased sensitivity and activity of the rods which occurred after sunset.

Three experiments used a free-choice technique to investigate effects of novelty on selective attention. Ss underwent a habituation phase, during which combinations of spots of one color were presented, and then a test phase, during which spots of the familiar color and a novel color were presented together. Experiment 1 showed that, during the test phase, Ss were more likely to respond to novel stimuli whether manual or verbal responses were performed in both phases. Experiment 2 produced the same effect with different distances between stimuli and the fixation point for the two phases, ruling out retinal adaptation as an explanation. Experiment 3 showed the effect to occur when different responses were performed in the two phases, indicating that it is stimulus-specific.

Human subjects were asked to identify one of seven possible luminance levels under Ganzfeld conditions. The luminance range investigated was 0.5–500.0 ft 1m. Earlier findings on the subjective effects of a Ganzfeld on humans were verified. Subjects performed significantly better under non-adapted than under adapted conditions. Under both conditions subjects tended to perform better after pupillary diameter had been fixed. Errors never exceeded 1 log10 unit in magnitude.

Visually evoked cortical potentials /VECP/ to different probe stimuli to suppressed human eye in binocular rivalry experiments, discussing eye dominance problems

A system has been devised for causing an image to remain at one point on the retina regardless of eye movements. A beam of light, reflected from a plane mirror on a contact lens, is used to project onto a screen an image of a dark line against a bright background. The screen is viewed by the same eye through an optical system which compensates for the doubling of the angle of rotation of the beam projected from the mirror on the contact lens. Thus, any motion of the eye causes a deviation of the beam such that the retinal image of the projected line undergoes the same displacement as do the retinal receptor cells. By comparison with normal viewing of the same test objects it is found that (1) when first presented, the finest lines are seen with normal or slightly better than normal acuity, (2) within a few seconds the lines begin to disappear, and (3) within one minute even coarse lines are seen only intermittently. The results may be interpreted in terms of local retinal adaptation to a stationary field.

The responses of rabbit striate cortex neurons to light or optic nerve shock were tested in 633 units in 54 rabbit pups 3–25 days of age. Units were driven by optic nerve shock at the youngest ages tested, but could not be driven by light until postnatal day eight. It was found that the symmetric receptive field types (concentric, uniform, motion) were present at or near the time of eye opening (10–11 days), while the asymmetric types (directional, simple, complex, oriented-directional) did not appear until several days later. All adult receptive field types were first seen at day 18. Until about day 20, cells with indefinite response properties were much more numerous than in the adult, and it is suggested thab cells with asymmetric receptive fields may differentiate out of the indefinite group. Development of visual response in the striate cortex is markedly retarded when compared to that in the superior colliculus.

When conflicting contours are projected to corresponding areas of the retinae through a stereoscopic device, S reports viewing not a stable figure but an irregular alternation that cannot be given a unitary interpretation. For example, if the conflicting contours are a vertical bar projected to the left eye and a horizontal bar projected to the right, rhen the phenomenal outcome is the periodic establishment of one bar as dominant and the total or partial suppression of the other. The experienced alternation in contour domrnance defines the phenomenon of bitaoczdm ("retinal") rivaky, and the total number of reversals or alternations per unit of time has been taken as an operational measure of the rate of binocz~lar rivahy. Historically, the phenomenon of binocular rivalry was linked with sensory threshold fluctuations and figure reversal and was accounted for merely as "fluctuations in the attention" (Helmholtz, 1925). However, Guilford ( 1927) demonstrated thac these three phenomena had nothing to do with attention but were a physiological function occurring only with liminal stimuli; a number of physiological conditions, both peripheral and central, were involved, among which were local retinal adaptation, eye movements, and local-central fatigue and inhibition. McDougall ( 1903) held thac the latter, local-central fatigue and inhibition, accounted for the phenomenon of "retinal" rivalry; but that the phenomenon is affected by so many other than physiological factors that no purely physiological explanation could be satisfactory. Recently, Linksz ( 1952, p. 549) has deplored the usage of the term "retinal rivalry" for the phenomenon and instead employs the term "cortical rivalry of retinal processes." The rivalry of the contours, he argues, is the phenomenal counterpart of opposing neurological gradients which cannot occupy the same cortical (or retinal) locus. Because of the limited neurological and physiological data in this area, the present writers have employed the more neutral and less objectional term, binocular rivalry, to describe the phenomenon. Although a number of studies have been conducted to determine rhe effects of rnv~ronmental variables, such as illumination level, figure-ground relationships, sc~mulus content, etc., on the rate of binocular rivalry, relatively few have been concerned with the inscri~ctions. Specifically, what is the effect of insuucrions on the reversal process? In his early work, Helmholtz (1925, p. 541) observed that he could voluntarily control the persistence of one visual field over the other, but he dismissed this ubiquitous finding as "simply a phenomenon of

A brilliantly colored Van Gogh or a flash of white light—how does the eye translate these into optic nerve impulses? The translation is done by "the immediate instrument of vision," the retina. This book deals with that translation process. The book is based on a symposium held at the dedication at the Jules Stein Institute at UCLA College of Medicine. It attracted many of the brightest names working in visual science today. Scanning the table of contents, one finds Dowling writing on the retinal ganglion cells, Mommaerts on the visual pigments, Dartnall and also Wald on visual photochemistry, Rushton on retinal adaptation, Hartline on retinal inhibitory interaction, Brown on the electroretinogram, Straatsma on the topography of the retina, Potts on clinical electroretinogram and electro-oculography, Linksz on acquired color blindness, and 12 other papers on related topics. The scholarly excellence of the contributed work, well edited and well published, is an