Velocity dependence of the interocular transfer of dynamic motion aftereffects

Habituation of visual adaptation

Our sensory system adjusts its function driven by both shorter-term (e.g. adaptation) and longer-term (e.g. learning) experiences. Most past adaptation literature focuses on short-term adaptation. Only recently researchers have begun to investigate how adaptation changes over a span of days. This question is important, since in real life many environmental changes stretch over multiple days or longer. However, the answer to the question remains largely unclear. Here we addressed this issue by tracking perceptual bias (also known as aftereffect) induced by motion or contrast adaptation across multiple daily adaptation sessions. Aftereffects were measured every day after adaptation, which corresponded to the degree of adaptation on each day. For passively viewed adapters, repeated adaptation attenuated aftereffects. Once adapters were presented with an attentional task, aftereffects could either reduce for easy tasks, or initially show an increase followed by a later decrease for demanding tasks. Quantitative analysis of the decay rates in contrast adaptation showed that repeated exposure of the adapter appeared to be equivalent to adaptation to a weaker stimulus. These results suggest that both attention and a non-attentional habituation-like mechanism jointly determine how adaptation develops across multiple daily sessions.

Unbiased Measures of Interocular Transfer of Motion Adaptation

Numerous studies have measured the extent to which motion aftereffects transfer interocularly. However, many have done so using bias-prone methods, and studies rarely compare different types of motion directly. Here, we use a technique designed to reduce bias (Morgan, 2013, Journal of Vision, 13(8):26, 1–11) to estimate interocular transfer (IOT) for five types of motion: simple translational motion, expansion/contraction, rotation, spiral, and complex translational motion. We used both static and dynamic targets with subjects making binary judgments of perceived speed. Overall, the average IOT was 65%, consistent with previous studies (mean over 17 studies of 67% transfer). There was a main effect of motion type, with translational motion producing stronger IOT (mean: 86%) overall than any of the more complex varieties of motion (mean: 51%). This is inconsistent with the notion that IOT should be strongest for motion processed in extrastriate regions that are fully binocular. We conclude that adaptation is a complex phenomenon too poorly understood to make firm inferences about the binocular structure of motion systems.

Three-dimensional motion aftereffects reveal distinct direction-selective mechanisms for binocular processing of motion through depth

Motion aftereffects are historically considered evidence for neuronal populations tuned to specific directions of motion. Despite a wealth of motion aftereffect studies investigating 2D (frontoparallel) motion mechanisms, there is a remarkable dearth of psychophysical evidence for neuronal populations selective for the direction of motion through depth (i.e., tuned to 3D motion). We compared the effects of prolonged viewing of unidirectional motion under dichoptic and monocular conditions and found large 3D motion aftereffects that could not be explained by simple inheritance of 2D monocular aftereffects. These results (1) demonstrate the existence of neurons tuned to 3D motion as distinct from monocular 2D mechanisms, (2) show that distinct 3D direction selectivity arises from both interocular velocity differences and changing disparities over time, and (3) provide a straightforward psychophysical tool for further probing 3D motion mechanisms.

The surface and deep structure of the waterfall illusion

The surface structure of the waterfall illusion or motion aftereffect (MAE) is its phenomenal visibility. Its deep structure will be examined in the context of a model of space and motion perception. The MAE can be observed following protracted observation of a pattern that is translating, rotating, or expanding/contracting, a static pattern appears to move in the opposite direction. The phenomenon has long been known, and it continues to present novel properties. One of the novel features of MAEs is that they can provide an ideal visual assay for distinguishing local from global processes. Motion during adaptation can be induced in a static central grating by moving surround gratings; the MAE is observed in the static central grating but not in static surrounds. The adaptation phase is local and the test phase is global. That is, localised adaptation can be expressed in different ways depending on the structure of the test display. These aspects of MAEs can be exploited to determine a variety of local/global interactions. Six experiments on MAEs are reported. The results indicated that relational motion is required to induce an MAE; the region adapted extends beyond that stimulated; storage can be complete when the MAE is not seen during the storage period; interocular transfer (IOT) is around 30% of monocular MAEs with phase alternation; large field spiral patterns yield MAEs with characteristic monocular and binocular interactions.

Transfer of the curvature aftereffect in dynamic touch

A haptic curvature aftereffect is a phenomenon in which the perception of a curved shape is systematically altered by previous contact to curvature. In the present study, the existence and intermanual transfer of curvature aftereffects for dynamic touch were investigated. Dynamic touch is characterized by motion contact between a finger and a stimulus. A distinction was made between active and passive contact of the finger on the stimulus surface. We demonstrated the occurrence of a dynamic curvature aftereffect and found a complete intermanual transfer of this aftereffect, which suggests that dynamically obtained curvature information is represented at a high level. In contrast, statically perceived curvature information is mainly processed at a level that is connected to a single hand, as previous studies indicated. Similar transfer effects were found for active and passive dynamic touch, but a stronger aftereffect was obtained when the test surface was actively touched. We conclude that the representation of object information depends on the exploration mode that is used to acquire information.

Intramanual and intermanual transfer of the curvature aftereffect

The existence and transfer of a haptic curvature aftereffect was investigated to obtain a greater insight into neural representation of shape. The haptic curvature aftereffect is the phenomenon whereby a flat surface is judged concave if the preceding touched stimulus was convex and vice versa. Single fingers were used to touch the subsequently presented stimuli. A substantial aftereffect was found when the adaptation surface and the test surface were touched by the same finger. Furthermore, a partial, but significant transfer of the aftereffect was demonstrated between fingers of the same hand and between fingers of both the hands. These results provide evidence that curvature information is not only represented at a level that is directly connected to the mechanoreceptors of individual fingers but is also represented at a stage in the somatosensory cortex shared by the fingers of both the hands.

Detecting structure in glass patterns: an interocular transfer study

Glass patterns are visual stimuli used here to study how local orientation signals are spatially integrated into global pattern perception. We measured a form aftereffect from adaptation to both static and dynamic Glass patterns and calculated the amount of interocular transfer to determine the binocularity of the detectors responsible for the perception of global structure. Both static and dynamic adaptation produced significant form aftereffects and showed a very high degree of interocular transfer, suggesting that Glass-pattern perception involves cortical processing beyond primary visual cortex. Surprisingly, dynamic adaptation produced significantly greater interocular transfer than static adaptation. Our results suggest a functional interaction between local orientation processing and global motion processing that contributes to form perception.

Test stimulus characteristics determine the perceived speed of the dynamic motion aftereffect

Using a speed-matching task, we measured the speed tuning of the dynamic motion aftereffect (MAE). The results of our first experiment, in which we co-varied dot speed in the adaptation and test stimuli, revealed a speed tuning function. We sought to tease apart what contribution, if any, the test stimulus makes towards the observed speed tuning. This was examined by independently manipulating dot speed in the adaptation and test stimuli, and measuring the effect this had on the perceived speed of the dynamic MAE. The results revealed that the speed tuning of the dynamic MAE is determined, not by the speed of the adaptation stimulus, but by the local motion characteristics of the dynamic test stimulus. The role of the test stimulus in determining the perceived speed of the dynamic MAE was confirmed by showing that, if one uses a test stimulus containing two sources of local speed information, observers report seeing a transparent MAE; this is despite the fact that adaptation is induced using a single-speed stimulus. Thus while the adaptation stimulus necessarily determines perceived direction of the dynamic MAE, its perceived speed is determined by the test stimulus. This dissociation of speed and direction supports the notion that the processing of these two visual attributes may be partially independent.

The simple perfection of quantum correlation in human vision

A theory is presented that specifies the amount of light that is needed for the perception of any stimulus that is defined in space, time and color. For detection and discrimination mechanistic neural elements with deterministic procedures exist. Twin pairs of red and green cones are ordered in three sets along clockwise and counter clockwise revolving spirals and along circles around the center of the fovea. In the rod-free fovea the red pairs are ordered along the spirals and the green along the circles. Each cone is accompanied by--dependent on retinal eccentricity--up to 100 satellite rods. For the retinal signal processing such a receptor group constitutes a space-quantum in analogy with time-quanta of about 0.04 s. In the peripheral retina the red and green twin pairs of space-quanta are roughly ordered along and at random distributed over the spirals and circles. Over each time-quantum, the cone and rods of a space-quantum sum their responses in a common nerve circuit of the luminosity channel. The summation's results from twin pairs of the same set of space-quanta are correlated by two-fold spatio-temporal coincidence mechanisms in the retina. Their outcome signals the perception of light, movement and edge. In the fused binocular visual field the movement and edge signals of the three sets from both eyes perfectly join vectorially together, provided the responding pairs of space-quanta are binocularly in perfect register as they normally are. The receptor's Weber gain control makes the receptor an all-or-none-system. The space-quantum's De Vries gain control makes its sensitivity equal to the average of the poisson fluctuations in quantum absorption per time-quantum. The controls are based on, respectively, arithmetically feed forward and backward inhibitive nerve mechanisms. The thermal noise of the photo-pigment resets the controls. The response to the second quantum absorption in a time-quantum in the individual rod, red or green cone has accession to the white, red or green nerve color circuit, respectively, and produces there a corresponding color signal. Already a single absorption in a blue cone is for a blue signal. In the retina, for the generation of yellow signals, the color circuits of individual red and green cones of each mixed entwined triple of red and green twin pairs of space-quanta are cross-connected through a nerve opponent color circuit. In the lateral geniculate nucleus in groups of seven neighboring triples, through two nerve opponent color circuits that are common for the two eyes together, the red and green signals as well as the yellow and blue mutually annihilate each other's color. White signals remain. In anomalous trichromacy, the space-quanta of some pairs have different cones or in one of them the cone is missing. In dichromacy, all pairs have different cones or one type of cones is missing. For perceptive resolution the periodic scanning of the retinal image by the eye tremor in synchrony with the time-quanta, overrules the limit of optical resolution as set by diffraction in the eye optics. Dependent on pupil diameter the scanning contributes up to a factor of about 30 to resolution. The action potentials of the Purkinje cells in the myocardium generate the time-quanta of the central nervous system as well as the mechanical scanning of the retinal image through the synchronic periodic variation of the tonus in the eye muscles.