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PubMed1985

Effect of localized grating adaptation as a function of separation along the length axis between test and adaptation areas.

Aftereffect following adaptation to localized gratings was measured as a function of the separation along the length axis between test and adaptation gratings. When the adaptation gratings were located on or near the retinal area occupied by the test grating, contrast sensitivity greatly decreased. When the adaptation gratings were spatially separated from the test grating, contrast sensitivity significantly increased. This property is similar to that which was observed in our previous study, in which the adaptation gratings were displaced from a test grating along the modulation axis. The facilitatory aftereffect of the grating adaptation can be accounted for by assuming that there may exist two mechanisms involved in the adaptation process; one is a center mechanism responsible for the detection of a test pattern, its adaptation producing a reduction in responsiveness; the other is a surround mechanism which tonically inhibits the center mechanism, its adaptation resulting in an increase in the sensitivity of the center mechanism by releasing the tonic inhibition. The spatial property of the adaptation effect may reflect the nature of spatial integration process of the center and surround mechanism.

Adaptation, Ocular↗
PubMed1985

A motion aftereffect from an isoluminant stimulus.

We investigate whether a motion aftereffect (MAE) can be induced by an isoluminant stimulus which contains colour contrast but no luminance contrast. We created a red/green chromatic stimulus, composed of red and green monochromatic grating added in antiphase, and corrected for the chromatic aberrations of the eye. We varied the ratio of the red to green luminances in the stimulus and found that there is no luminance ratio at which the MAE disappears. The results suggest that isoluminant stimuli can induce a MAE which is as great and sometimes greater than that induced by luminance contrast.

Color↗
PubMed1996

Adaptive spatial alignment and strategic perceptual-motor control.

When starting limb and target locations were simultaneously visible in a visuomotor task, performance during prism exposure was nearly perfect, but aftereffects were absent. When starting limb location was not visible, accurate exposure performance was slow to develop, but aftereffects were substantial. Adaptive spatial alignment of sensorimotor spaces and strategic perceptual-motor control to coordinate sensorimotor systems are distinct processes. However, realignment is dependent on whether the exposure task evokes control strategies that enable detection of misalignment. If the task can be performed solely by coding the visible difference between limb and target locations, misalignment detection is disabled. If movement is initiated by target location and then the limb is controlled by the visible difference between target and limb, the discordance between initialized and terminal locations enables misalignment detection and realignment.

Adult↗
PubMed1977

Visual motion aftereffect induced by simulated rectilinear motion.

Visual motion aftereffect characteristics comparable to those associated with rotary and translatory movement of a test field are demonstrated for simulated rectilinear motion of the observer. The intensity and time duration of the phenomenon are shown to be positively correlated. The implications of this for individual observers are considered. The results of this experiment are correlated with those for adaptation and for recovery from adaptation that were obtained from the same group of observers. The findings are shown to support the hypothesis that visual motion affereffect is a manifestation of the adaptation recovery function of velocity sensitive mechanisms.

Adult↗
PubMed2005

Perceptual manifestations of fast neural plasticity: motion priming, rapid motion aftereffect and perceptual sensitization.

Visual neurons show fast adaptive behavior in response to brief visual input. However, the perceptual consequences of this rapid neural adaptation are less known. Here, we show that brief exposure to a moving adaptation stimulus-ranging from tens to hundreds of milliseconds-influences the perception of a subsequently presented ambiguous motion test stimulus. Whether the ambiguous motion is perceived to move in the same direction (priming), or in the opposite direction (rapid motion aftereffect) varies systematically with the duration of the adaptation stimulus and the adaptation-test blank interval. These biases appear and decay rapidly. Moreover, when the adapting stimulus is itself ambiguous, these effects are not produced. Instead, the percept for the subsequent test stimulus is biased to the perceived direction of the adaptation stimulus. This effect (perceptual sensitization) builds gradually over the time between the adaptation and test stimuli. Our results indicate that rapid adaptation plays a role mainly within early motion processing, whereas a slow potentiation controls the sensitivity at a later stage.

Adaptation, Physiological↗
PubMed2000

The network of brain areas involved in the motion aftereffect.

A network of brain areas is expected to be involved in supporting the motion aftereffect. The most active components of this network were determined by means of an fMRI study of nine subjects exposed to a visual stimulus of moving bars producing the effect. Across the subjects, common areas were identified during various stages of the effect, as well as networks of areas specific to a single stage. In addition to the well-known motion-sensitive area MT the prefrontal brain areas BA44 and 47 and the cingulate gyrus, as well as posterior sites such as BA37 and BA40, were important components during the period of the motion aftereffect experience. They appear to be involved in control circuitry for selecting which of a number of processing styles is appropriate. The experimental fMRI results of the activation levels and their time courses for the various areas are explored. Correlation analysis shows that there are effectively two separate and weakly coupled networks involved in the total process. Implications of the results for awareness of the effect itself are briefly considered in the final discussion.

Adult↗
PubMed2005

Global orientation aftereffect in multi-attribute displays: implications for the binding problem.

We investigated the binding problem (e.g. the combination of edge information across attributes), using an orientation aftereffect paradigm (OAE). Horizontal layers of vertical edges were phase-shifted to create a global near-vertical orientation. Multi-attribute displays were created by alternating the attribute defining edges (e.g. luminance, colour, texture or motion) across layers. OAE magnitude was dependent only on the attributes used in the adaptation phase, and the similarity of attributes from adaptation to testing phase had no significant effect. Moreover, compared to single-attribute conditions, the cooperation between attributes is moderate. These results favour segregation models of the binding mechanism.

Adaptation, Physiological↗
PubMed1981

Interlimb transfer after adaptation to visual displacement: patterns predicted from the functional closeness of limb neural control centres.

Two experiments were designed to determine whether interlimb transfer of prism adaptation follows a pattern predicted by the functional closeness of limb control centres. Subjects were adapted to a lateral displacing prism with their right arm in conditions known to facilitate interlimb transfer. Negative aftereffect measures of target-pointing shift were taken for all limbs. If transfer to the unadapted limbs is primarily the result of some sort of visual change, scores for those limbs should not differ. However, if the functional cerebral closeness of limb control centres is a factor, the greatest shift should be evidenced in the homologous contralateral limb (left arm), followed by the ipsilateral limb (right leg), with the least shift to the diagonally opposite limb (left leg). No differences in shift among the three unadapted limbs was found in the two experiments.

Adaptation, Ocular↗
PubMed2006

Visual recalibration and selective adaptation in auditory-visual speech perception: Contrasting build-up courses.

Exposure to incongruent auditory and visual speech produces both visual recalibration and selective adaptation of auditory speech identification. In an earlier study, exposure to an ambiguous auditory utterance (intermediate between /aba/ and /ada/) dubbed onto the video of a face articulating either /aba/ or /ada/, recalibrated the perceived identity of auditory targets in the direction of the visual component, while exposure to congruent non-ambiguous /aba/ or /ada/ pairs created selective adaptation, i.e. a shift of perceived identity in the opposite direction [Bertelson, P., Vroomen, J., & de Gelder, B. (2003). Visual recalibration of auditory speech identification: a McGurk aftereffect. Psychological Science, 14, 592-597]. Here, we examined the build-up course of the after-effects produced by the same two types of bimodal adapters, over a 1-256 range of presentations. The (negative) after-effects of non-ambiguous congruent adapters increased monotonically across that range, while those of ambiguous incongruent adapters followed a curvilinear course, going up and then down with increasing exposure. This pattern is discussed in terms of an asynchronous interaction between recalibration and selective adaptation processes.

Adaptation, Physiological↗
PubMed1994

Illusory, motion, and luminance-defined contours interact in the human visual system.

Psychophysical studies of interactions between contours defined by different image attributes report that luminance-defined and illusory contours show little if any interaction. Because the contours defined by these attributes may vary in perceptual saliency, we employed the tilt aftereffect (TAE) and a cross-adaptation procedure to evaluate interaction effects between luminance-defined and illusory contours under varying saliency conditions as well as to explore the interaction between illusory and motion-defined contours. When contour salience of the adaptation or test stimuli was modified by the addition of various amounts of static noise, we observed a TAE for all combinations of contour types including the novel motion-illusory and illusory-motion pairs. The interactions demonstrated between the contour classes in this as well as other studies suggests contour invariance in the orientation domain.

Adaptation, Ocular↗
PubMed2003

Adaptation to vertical disparity induced-depth: implications for disparity processing.

Depth aftereffects produced by prolonged inspection of an object in depth can be mediated by monocular and binocular depth cues. The adapting mechanisms responsible for such effects have not yet been fully determined. Theories of binocular depth aftereffects typically posit a role of an adaptive horizontal disparity sensitive mechanism, implying multiple cue-specific mechanisms for depth aftereffects. Here we examined whether binocular depth aftereffects can be attributed to such a cue-specific mechanism. In Experiment 1 we did so using a technique allowing us to maintain horizontal disparities and vergence constant for our adaptation stimuli, whilst manipulating simulated depth by virtue of a vertical disparity induced-depth effect. We found that depth aftereffects were almost identical to those produced by adaptation to stimuli of equivalent depth produced by conventional horizontal disparity modulations. In Experiment 2, we examined depth aftereffects following adaptation to apparently frontal surfaces produced by different combinations of horizontal and vertical disparity modulations. Aftereffects were close to zero. These results suggest that binocular depth aftereffects are not due to adaptation of a horizontal disparity sensitive mechanism, and we argue that adaptation occurs at the level of a 3D shape sensitive mechanism derived from multiple cues. Experiment 3 was a control to examine whether the two types of adaptation stimuli in Experiment 1 were indeed perceptually the same, since in theory they may differ if vertical disparities influenced metric depth scaling. We found no evidence of this, and concluded that the two classes of stimuli used in Experiment 1, though consisting of very different patterns of disparity, were perceptually equivalent.

Adaptation, Physiological↗
PubMed1984

Short test flashes produce large tilt aftereffects.

Using a staircase method, the tilt aftereffect (TAE) was measured with test flashes of durations ranging from 10 to 600 msec. The TAE is largest with brief duration test stimuli and reaches an asymptotic value at a test flash duration of 200-300 msec. A series of control experiments rule out a variety of explanations for this finding. The decline in TAE magnitude with increasing test duration is not due to decay, nor can the large TAEs produced by brief stimuli be explained in terms of their lower effective luminance or contrast. The results suggest that brief stimuli are processed by a different subset of processes or channels than are longer stimuli.

Adaptation, Ocular↗
PubMed1989

The effects of exposure duration and surrounding frames on direct and indirect tilt aftereffects and illusions.

Direct and indirect tilt illusions (TIs) have been shown to have different mechanisms, because spatial parameters that affect the one do not affect the other, and vice versa. The indirect TI, for example, is reduced markedly by a surrounding vertical square frame, a manipulandum that has no effect on the direct TI (Wenderoth & Johnstone, 1988a). In six experiments, we show that both direct and indirect TIs are enhanced in magnitude with short (10-60 msec) exposures; that tilt aftereffects (TAEs) induced with short test exposures are entirely comparable in magnitude; that a surrounding square frame reduces indirect TAEs but not direct TAEs, just as occurs with the TI; and that when the surrounding frame is present during adaptation only, test only, and both or neither, the greatest indirect TAE reduction occurs when the frame is present during the test. These results are consistent with the view (Wenderoth & Johnstone, 1987, 1988a, 1988b) that indirect TIs and TAEs may not reflect temporary neural modification based on V1 lateral inhibitory processes but rather the operation of more global, possibly extrastriate, orientation-constancy mechanisms.

Adult↗
PubMed1996

The effect of dark and equiluminant occlusion on the interocular transfer of visual aftereffects.

Lehmkuhle and Fox [(1976) Vision Research, 16, 428-430] reported that interocular transfer (IOT) of a translational motion aftereffect (MAE) was greater if the non-adapting eye viewed an equiluminant field than if it viewed a dark field. They recommended equiluminant occlusion of the non-adapted eye when measuring IOT of aftereffects. We tested this proposal in three experiments. First, we assessed IOT with equiluminant and dark occlusion for three different classes of aftereffects. Although transfer was greater with equiluminant occlusion for the translational MAE, there was no significant difference in the amount of transfer for the tilt aftereffect or the contrast threshold elevation effect. Second, we tested the hypothesis that spuriously large IOT could be the result of an aftereffect from tracking eye movements in the non-adapting eye. When potential tracking movements were reduced by using rotating spokes, a rotating spiral or contracting concentric circles, there was a corresponding reduction in the occlusion-dependent transfer. Third, we found that luminance shifts had no influence on the amount of transfer when all contours were eliminated from the non-adapting eye. We conclude that the type of occlusion used for measuring IOT of the translational MAE is important only when visible contours in the non-adapting eye contribute to the adapting process.

Adaptation, Ocular↗
PubMed1996

Spatial filter combination in human pattern vision: channel interactions revealed by adaptation.

Above threshold, two superimposed sinusoidal gratings of the same spatial frequency (eg 1 cycle deg-1), of equal moderate contrast (eg C1 = C2 = 6%), and with orientations of +/- 45 degrees, usually look like a compound structure containing vertical and horizontal edges (ie a blurred checkerboard). These feature orientations are very different from the dominant filter orientations in a wavelet-type (eg simple-cell) transform of the stimulus, and so present a serious challenge to conventional models of orientation coding based on labelled linear filters. Previous experiments on perceived structure in static plaids have led to the view that the outputs of tuned spatial filters are combined in a stimulus-dependent way, before features such as edges are extracted. Here an adaptation paradigm was used to investigate the cross-channel interactions that appear to underlie the spatial-filter-combination process. Reported are two aftereffects of selective adaptation: (i) adaptation to a 1 cycle deg-1 plaid whose component orientations are intermediate to those in a 1 cycle deg-1 test plaid 'breaks' perceptual combination of the components in the test plaid; (ii) adapting to a 3 cycles deg-1 plaid whose component orientations match those in a 1 cycle deg-1 test plaid facilitates perceptual combination of the components in the test plaid. The results are taken as evidence that spatial channels remote from those most responsive to a test plaid play a crucial role in determining whether the test plaid segments or coheres perceptually.

Adaptation, Ocular↗
PubMed1983

Separate motion aftereffects from each eye and from both eyes.

UNLABELLED: Monocular and binocular motion aftereffects (MAEs) are described, which were contingent upon which eye(s) was (were) exposed to the adapting motion. Subjects viewed clockwise rotation of a patterned disc with their left eye, alternating every 5 sec with anticlockwise rotation seen with their right eye, for a 10-min adapting period. RESULT: they saw an anticlockwise motion aftereffect with their left eye, and a clockwise MAE with their right eye. These monocular MAEs lasted for only 2-20 sec, but could be elicited repeatedly over a 2-6 min period, and could still be re-elicited two hours later. In a second experiment, subjects adapted for 10 min to the following cycle of 5-sec rotations: left eye, clockwise: right eye, clockwise: and both eyes together, anticlockwise. RESULT: they saw an anticlockwise MAE with their left eye only or with their right eye only, and a clockwise MAE when both eyes were open. A model of monocular and binocular inputs to motion sensitive neural channels is proposed.

Adaptation, Ocular↗
PubMed1998

The indirect McCollough effect: an examination of an associative account.

It has been found that viewing, for example, a red-and-black vertical grating alternating with a green homogeneous field produces a color aftereffect--a McCollough effect--on a black-and-white vertical grating (i.e., green). Viewing such colored patterns also produces an aftereffect on a noninduced horizontal grating (i.e., pink)--the indirect McCollough effect. Humphrey, Dodwell, and Emerson (1989) argued that the indirect McCollough effect is caused by opponent properties of the visual system that organize the processing of contour and color along contrasting, probably orthogonal, dimensions. Recently, however, their interpretation of the indirect McCollough effect has been challenged by some findings of Eissenberg, Allan, Siegel, and Petrov (1995). These researchers have proposed that the indirect McCollough effect, like the McCollough effect, can be explained by associative principles. The results reported here question crucial aspects of the hypothesis of Eissenberg et al.

Afterimage↗
PubMed1992

Shape discrimination and the judgement of perfect symmetry: dissociation of shape from size.

We measured the accuracy with which subjects judged that a square or circle was perfectly symmetrical i.e. that aspect ratio (a/b) was exactly unity (where a and b were, respectively, the vertical and horizontal dimensions). Errors were remarkably small, ranging from 0.7 to 0.4% for the judgement of squareness and from 1.4 to < 0.1% for the judgement of circularity. Precision in judging aspect ratio was measured by requiring subjects to judge whether the aspect ratio (a/b)TEST of a test rectangle was greater or less than the aspect ratio (a/b)REF of a reference rectangle. Similar measurements were made for elliptical targets. To ensure that subjects based judgements on aspect ratio rather than a, b or (a-b), the area of each successive presentation was varied randomly. The just-discriminable percentage change of aspect ratio was as low as 1.6% at (a/b)REF = 1.0 (i.e. for a square or circular reference), and rose progressively as (a/b)REF was made progressively larger or smaller than 1.0. Aspect ratio discrimination threshold was independent of mean area over a sixteen-fold range of 0.25-4.0 deg2. For both rectangles and ellipses, the best value of aspect ratio discrimination threshold corresponded to a precision of encoding a and b of 14 sec arc or better. In further experiments, the method of constant stimuli was used to measure an aspect ratio aftereffect produced by adapting separately to rectangles of (a/b)ADAPT equal to 1.5, 1.0 and (1/1.5). Similar aftereffects were obtained whether the area of the test stimulus was fixed or varied randomly from trial to trial, and whether the test stimulus was rectangular or elliptical. The aftereffect could not be explained in terms of fatigue of neurons sensitive to linear dimension a or b. Nor could the aftereffect be explained in terms of the "contour repulsion" hypothesis, or in terms of orientation discrimination. We conclude (1) that the same neural mechanism determines aspect ratio discrimination threshold for rectangles and ellipses and (2) that this mechanism is sensitive to aspect ratio independently of linear dimensions. We propose that aspect ratio perception is determined by the balance of excitation of two pools of neurons that are selectively sensitive to different, but overlapping ranges of (a/b). One pool prefers aspect ratios > 1.0 and the others prefer aspect ratios < 1.0. We suppose that the two pools respond identically to changes in area (a * b).(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Ocular↗