Interocular transfer of visual aftereffects

A number of the well-known visual after-effects of adaptation exhibit interocular transfer, so that presentation of an adaptation figure to one eye produces a temporary change in the performance of the nonadapted eye. This outcome is usually attributed to the involvement of binocular visual neurons that respond to stimulation of either eye. The fact that interocular transfer is incomplete (i.e., the transferred aftereffect is smaller in magnitude than that induced and measured in the same eye) is routinely cited as evidence for the involvement of monocular neurons. This article critically examines these two interpretations, which are developed in terms of a neural model of interocular transfer. No evidence, logical or empirical, was obtained for rejecting the model. Our analysis further shows that the model must assume some type of pooling process that operates over all tested neurons, both adapted and unadapted. Finally, general implications of the interocular transfer model are discussed, the aim being to delimit the conclusions that may be drawn from interocular transfer experiments.     

Interdigital transfer of kinesthetic after-effects

Two experiments investigated the effect of using a different finger for inspection (I) than is used in making judgments on the size of a kinesthetic aftereffect (KAE). Experiment I investigated transfer of I stimulation of the ring finger to judgments made with the index finger, A control group used the index finger for both judgments and 1 period. Results indicated significant KAE for both groups. Experiment II replicated Experiment I except the second finger was used to test for transfer of I stimulation to judgments made with the index finger. Results indicated KAE for only the control group which used the index finger for both judgments and 1 stimulation.     

Interdigital transfer of kinesthetic after-effects

Two experiments investigated the effect of using a different finger for inspection (I) than is used in making judgments on the size of a kinesthetic aftereffect (KAE). Experiment I investigated transfer of I stimulation of the ring finger to judgments made with the index finger, A control group used the index finger for both judgments and I period. Results indicated significant KAE for both groups. Experiment II replicated Experiment I except the second finger was used to test for transfer of I stimulation to judgments made with the index finger. Results indicated KAE for only the control group which used the index finger for both judgments and I stimulation.     

Interocular transfer of discriminations in the pigeon

Pigeons with one eye covered were trained to discriminate intensities or colors of stimuli located to one side of the head, or intensities, colors or forms of stimuli located in front of the beak. Each discrimination transferred to the covered eye, even when previous training with the covered eye included the reversal of the tested discrimination. Pigeons also were able to learn conditional discriminations in which appropriate responding depended on which eye was covered.     

Interocular transfer of orientation-contingent color aftereffects with external and internal adaptation

The issue of whether McCollough effects transfer interocularly was examined in two experiments. In Experiment 1, as in previous experiments, no interocular transfer of McCollough effects was obtained when subjects adapted monocularly to externally present patterns with their unused eyes fully occluded. However, when subjects adapted monocularly (with the unused eye fully occluded) to visual images of those patterns superimposed on physically present chromatic backgrounds, McCollough effects transferred interocularly. In Experiment 2, subjects adapted to either physically present patterns or to images of those patterns (as in Experiment 1), but the unused eye was exposed to unpatterned diffuse white light. In contrast to Experiment 1, the externally adapted subjects showed interocular transfer of McCollough effects. In Experiment 2, the magnitude of the interocular transfer effects produced by imagery was significantly larger than the magnitude of the effects produced by external adaptation, but the magnitude of the imagery-induced aftereffects did not differ from Experiment 1 to Experiment 2. These results extend earlier findings by Kunen and May (1980) and show that McCollough effects can be produced through adaptation to imagery, even though the direction of the imagery-induced aftereffects indicates adaptation to higher spatial frequencies whereas externally derived aftereffects indicate adaptation to lower spatial frequencies. It is concluded that failure of previous studies to obtain interocular transfer of McCollough effects may have resulted from complete occlusion of the contralateral eye. These data point up some interesting similarities and some important differences between imagery and actual vision. The implications for analogical models of visual imagery are discussed.     

Interocular transfer of a rotational motion aftereffect as a function of eccentricity

In previous psychophysical investigations it has been reported that the angular extent over which the human visual field is served by binocular neurons in the visual cortex is limited to the central 40 degrees. However, these reports have been primarily based on data collected with static stimuli. Here we extend this investigation to include dynamic stimuli. Interocular transfer of the rotary motion aftereffect (rMAE) was measured for three stimulus diameters: 5, 30, and 62 deg. Interocular transfer, expressed as a percentage of monocular adapt/test rMAE duration was significantly reduced for stimulus diameter of 62 deg relative to 30 and 5 deg diameters. Nevertheless, interocular transfer durations still comprised a significant percentage of same-eye adapt/test durations (46.9%), comparable to previous reports of transfer MAE durations in near-central vision. The spatial extent of binocular interaction is likely stimulus specific and is still appreciable in the far periphery for complex-motion stimuli.     

The after-effects of ventriloquism

Subjects were tested for both ear-hand and eye-hand co-ordination before and after monitoring a synchronous series of noise bursts and of light flashes coming from the same spatial position, but with the virtual position of the flashes displaced 15° laterally by prisms. Attention was forced on both stimuli by the instruction to detect occasional reductions in intensity. No subject reported noticing the spatial discrepancy. Nevertheless ear--hand co-ordination was shifted in the direction of the prismatic displacement, and eye-hand co-ordination in the opposite direction. Both shifts were observed with instructions suggesting that the sound and the light came from one single source, with instructions suggesting two separate sources, and also with no information regarding the spatial relationship of sound and light. It is concluded that the resolution of auditory-visual spatial conflict involves recalibrations of both visual and auditory data and that these alterations last long enough to be detected as after-effects.     

Movement after-effects in normal development

Summary Fifty-one blindfolded children between the ages of 5 and 13 years pointed straight ahead before and after 10 trials of pointing asymmetrically to the body midline. It was found that whereas the younger children showed after-effect shifts in the direction opposite to the side of assymetrical stimulation, the older children's after-effect shifts were on the same direction as the previous asymmetrical pointing position.