Characterizing the effects of multidirectional motion adaptation

Journal of Vision, 2009

Prolonged exposure to a moving stimulus can substantially alter the perceived velocity (both speed and direction) of subsequently presented stimuli. Here, we show that these changes can be parsimoniously explained with a model that combines the effects of two isomorphic adaptation mechanisms, one nondirectional and one directional. Each produces a pattern of velocity biases that serves as an observable "signature" of the corresponding mechanism. The net effect on perceived velocity is a superposition of these two signatures. By examining human velocity judgments in the context of different adaptor velocities, we are able to separate these two signatures. The model fits the data well, successfully predicts subjects' behavior in an additional experiment using a nondirectional adaptor, and is in agreement with a variety of previous experimental results. As such, the model provides a unifying explanation for the diversity of motion aftereffects.

The processing of motion information by the visual system can be decomposed into two general stages; point-by-point local motion extraction, followed by global motion extraction through the pooling of the local motion signals. The direction aftereffect (DAE) is a well known phenomenon in which prior adaptation to a unidirectional moving pattern results in an exaggerated perceived direction difference between the adapted direction and a subsequently viewed stimulus moving in a different direction. The experiments in this paper sought to identify where the adaptation underlying the DAE occurs within the motion processing hierarchy. We found that the DAE exhibits interocular transfer, thus demonstrating that the underlying adapted neural mechanisms are binocularly driven and must, therefore, reside in the visual cortex. The remaining experiments measured the speed tuning of the DAE, and used the derived function to test a number of local and global models of the phenomenon. Our data provide compelling evidence that the DAE is driven by the adaptation of motion-sensitive neurons at the local-processing stage of motion encoding. This is in contrast to earlier research showing that direction repulsion, which can be viewed as a simultaneous presentation counterpart to the DAE, is a global motion process. This leads us to conclude that the DAE and direction repulsion reflect interactions between motion-sensitive neural mechanisms at different levels of the motion-processing hierarchy.

Journal of Neurophysiology, 2012

Prolonged exposure to a single direction of motion alters perception of subsequent static or dynamic stimuli and induces substantial changes in behaviors of motion-sensitive neurons, but the origin of neural adaptation and neural correlates of perceptual consequences of motion adaptation in human brain remain unclear. Using functional magnetic resonance imaging, we measured motion adaptation tuning curves in a fine scale by probing changes in cortical activity after adaptation for a range of directions relative to the adapted direction. We found a clear dichotomy in tuning curve shape: cortical responses in early-tier visual areas reduced at around both the adapted and opposite direction, resulting in a bidirectional tuning curve, whereas response reduction in high-tier areas occurred only at around the adapted direction, resulting in a unidirectional tuning curve. We also found that the psychophysically measured adaptation tuning curves were unidirectional and best matched the cort...

Attention, perception & psychophysics, 2014

It has been shown that humans cannot perceive more than three directions from a multidirectional motion stimulus. However, it remains unknown whether adapting to such imperceptible motion directions could generate motion aftereffects (MAEs). A series of psychophysical experiments were conducted to address this issue. Using a display consisting of randomly oriented Gabors, we replicated previous findings that observers were unable to perceive the global directions embedded in a five-direction motion pattern. However, adapting to this multidirectional pattern induced both static and dynamic MAEs, despite the fact that observers were unaware of any global motion directions during adaptation. Furthermore, by comparing the strengths of the dynamic MAEs induced at different levels of motion processing, we found that spatial integration of local illusory signals per se was sufficient to produce a significant global MAE. These psychophysical results show that the generation of a directional...

Current Biology, 2012

In Li and Atick's [1, 2] theory of efficient stereo coding, the two eyes' signals are transformed into uncorrelated binocular summation and difference signals, and gain control is applied to the summation and differencing channels to optimize their sensitivities. In natural vision, the optimal channel sensitivities vary from moment to moment, depending on the strengths of the summation and difference signals; these channels should therefore be separately adaptable, whereby a channel's sensitivity is reduced following overexposure to adaptation stimuli that selectively stimulate that channel. This predicts a remarkable effect of binocular adaptation on perceived direction of a dichoptic motion stimulus . For this stimulus, the summation and difference signals move in opposite directions, so perceived motion direction (upward or downward) should depend on which of the two binocular channels is most strongly adapted, even if the adaptation stimuli are completely static. We confirmed this prediction: a single static dichoptic adaptation stimulus presented for less than 1 s can control perceived direction of a subsequently presented dichoptic motion stimulus. This is not predicted by any current model of motion perception and suggests that the visual cortex quickly adapts to the prevailing binocular image statistics to maximize informationcoding efficiency.

Vision Research, 1994

Following a period of adaptation to a pattern moving in a particular direction, a subsequently viewed stationary pattern appears to move in the opposite direction for some time: the movement after effect (MAE). The MAE lasts longer when tbe test pattern is not imm~ately or not ~ontinuo~y presented after adaptation. This phenomenon is called storage. So far research indicates that storage oJy occurs when textured visual stimulation is absent during part of the test phase or if the processing of a stationary test stimulus is prevented (e.g. by binocular rivalry). We present evidence that storage-like phenomena can occur even while a textured and moving visual stimulus is phenomenally present. We adapted binocularly to uni~irection~ motion of a random-pixel array Ml for 60 sec. This stimulus was imm~ate~y followed by another moving pattern M2. Its motion direction was o~onaf to that of Ml. The presentation time of M2 was the independent variable. A stationary pattern was presented immediately after presentation of M2. The direction of the resulting integrated unidirectional MAE was measured. For short presentation times of M2 there is an integrated unidirectional MAE, which shows an interaction of the output of units stimulated by both moving patterns. However, it appeared that the effect of Ml on the direction of this combined unidirectional MAE is much longer present than would be expected from the MAE duration of Ml, when tested in i~lation.

Journal of Vision, 2009

Although contingent aftereffects between motion and stereopsis have been referred to as behavioral evidence for the joint processing of the two features, the reciprocal nature of encoding the two features has not been systematically studied. Using a novel form of concurrent adaptation, we probed the perception of direction-and disparity-defined coherent surfaces in parallel before and after adaptation to a stimulus that moved in a single direction at a particular binocular disparity. Contrary to earlier findings, we found a strong asymmetry between motion and stereopsis: the detection of disparity signal after adaptation was more impaired when the test stimulus was moving in the adapted direction than in the non-adapted direction, whereas the test disparity hardly affected the detection of coherent motion. However, motion adaptation became dependent on disparity when we added another surface that was moving in the opposite direction at the opposite sign of disparity to those of the original adaptor, as in previous studies of contingent aftereffects. The observed asymmetric contingency between motion and disparity adaptation urges the reinterpretation of previously reported contingent aftereffects and suggests a corresponding asymmetry between neural mechanisms devoted to processing of motion and stereopsis in human visual cortex.

Vision research, 1996

Across four experiments, this study investigated direction-specific adaptation and simultaneous contrast induced by moving binocular disparity information (stereoscopic motion). The stimuli were moving arrays of stereoscopic dots created from dynamic random-element stereograms. Experiments 1 and 2 examined the effects of adaptation to motion in a given direction on the apparent direction of test motion. Results showed that the direction of test motion appeared repulsed away from the direction of adapting motion (repulsion aftereffect) by as much as 20 deg or more when directions of adapt and test were similar. Experiment 3 investigated transfer of the repulsion aftereffect across the stereoscopic and luminance domains by employing stereoscopic adapting motion and luminance test motion or vice versa. Results showed that the repulsion aftereffect transferred across the two stimulus domains. Experiment 4 investigated direction-specific contrast by measuring the perceived direction of t...

Journal of Vision, 2011

Neural adaptation plays an important role in multistable perception, but its effects are difficult to discern in sequences of perceptual reversals. Investigating the multistable appearance of kinetic depth and binocular rivalry displays, we introduce cumulative history as a novel statistical measure of adaptive state. We show that cumulative historyVan integral of past perceptual states, weighted toward the most recent statesVsignificantly and consistently correlates with future dominance durations: the larger the cumulative history measure, the shorter are future dominance times, revealing a robust effect of neural adaptation. The characteristic time scale of cumulative history, which may be computed by Monte Carlo methods, correlates with average dominance durations, as expected for a measure of neural adaptation. When the cumulative histories of two competing percepts are balanced, perceptual reversals take longer and their outcome becomes random, demonstrating that perceptual reversals are fluctuation-driven in the absence of adaptational bias. Our findings quantify the role of neural adaptation in multistable perception, which accounts for approximately 10% of the variability of reversal timing.

Vision Research, 1998

Adaptation to a moving visual pattern induces shifts in the perceived motion of subsequently viewed moving patterns. Explanations of such effects are typically based on adaptation-induced sensitivity changes in spatio-temporal frequency tuned mechanisms (STFMs). An alternative hypothesis is that adaptation occurs in mechanisms that independently encode direction and speed (DSMs). Yet a third possibility is that adaptation occurrs in mechanisms that encode 2D pattern velocity (VMs). We performed a series of psychophysical experiments to examine predictions made by each of the three hypotheses. The results indicate that: (1) adaptation-induced shifts are relatively independent of spatial pattern of both adapting and test stimuli; (2) the shift in perceived direction of motion of a plaid stimulus after adaptation to a grating indicates a shift in the motion of the plaid pattern, and not a shift in the motion of the plaid components; and (3) the 2D pattern of shift in perceived velocity radiates away from the adaptation velocity, and is inseparable in speed and direction of motion. Taken together, these results are most consistent with the VM adaptation hypothesis.