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PubMed1997

Isoluminance and contingent color aftereffects.

In the typical induction of the orientation-contingent color aftereffect (CCAE), the stimuli are composed of elements that differ in both color and luminance. Three experiments are reported that show that chromatic contrast between stimulus elements is insufficient for the induction of the orientation-CCAE and that luminance contrast is necessary. These experiments expand on previous research concerned with the role of luminance contrast in the induction of orientation-CCAEs by eliminating alternative explanations.

Adult↗
PubMed1988

Amnesia for the McCollough effect following unilateral electroconvulsive therapy: implications for laterality.

The hemispheric lateralization of retrograde amnesia following unilateral electroconvulsive therapy (ECT) was measured by a novel nonverbal probe, the McCollough effect, which allowed equal and exclusive access to each hemisphere. Alternating exposure to perpendicular gratings of complementary colors (e.g., red vertical stripes alternated with green horizontal stripes) will cause subsequently presented black and white gratings to appear colored hours or even days later (the McCollough effect). Three of the patients examined (3 of 10) lost the effect in just the half visual field contralateral to the treatment side when unilateral nondominant ECT was interposed between the induction of the effect and the its test. Six patients lost the effect bilaterally following unilateral ECT. One patient retained a bilateral aftereffect. This patient had by far the shortest seizure (18 sec). Nine of 10 comparison patients, also suffering from major depression but without ECT intervening between induction and test, showed good bilateral retention of the McCollough effect. The remaining comparison patients showed no retention. These results imply that despite bilateral cortical spread of seizure activity, unilateral nondominant ECT has effects that are most pronounced over the stimulated hemisphere.

Adult↗
PubMed2005

Adaptive modulation of color salience contingent upon global form coding and task relevance.

Extensive research on local color aftereffects has revealed perceptual consequences of opponent color coding in the retina and the LGN, and of orientation-and/or spatial-frequency-contingent color coding in early cortical visual areas (e.g., V1 and V2). Here, we report a color aftereffect that depends crucially on global-form-contingent color processing. Brief viewing of colored items (passively viewed, ignored, or attended) reduced the salience of the previewed color in a subsequent task of color-based visual search. This color-salience aftereffect was relatively insensitive to variations (between color preview and search) in local image features, but was substantially affected by changes in global configuration (e.g. the presence or absence of perceptual unitization); the global-form dependence of the aftereffect was also modulated by task demands. The overall results suggest that (1) color salience is adaptively modulated (from fixation to fixation), drawing attention to a new color in visual-search contexts, and (2) these modulations seem to be mediated by global-form-and-color-selective neural processing in mid to late stages of the ventral visual pathway (e.g., V4 and IT), in combination with task-dependent feedback from higher cortical areas (e.g., prefrontal cortex).

Attention↗
PubMed1983

Aftereffect of induced rotation: number of radial lines in inducing stimulus.

Duration of aftereffect of induced rotation was shown to increase with the number of uniformly-spaced radial lines in an inducing stimulus. Possible explanations could be based on (a) the amount of shearing between radial lines in the inducing and static stimuli during adaptation, or (b) the angular displacement required for the inducing stimulus to assume again its initial form. Results for 5 women and 3 men from an inducing stimulus with non-uniformly spaced radial lines suggested that (a) was more important.

Adult↗
PubMed1994

On the contribution of a binocular 'AND' channel at contrast threshold.

Three experiments are reported in which an attempt was made to isolate the contribution of an AND channel by measuring aftereffects following alternating monocular adaptation. The first two were designed to test Wolf and Held's proposal that the binocular AND channel does not respond at contrast threshold. In the first experiment the relative sizes of monocular and binocular contrast threshold elevation were compared with the pattern of aftereffects obtained in a study of the suprathreshold tilt aftereffect. Identical patterns of results were obtained under the two adaptation conditions. In the second experiment, the monocular and binocular contrast-reduction aftereffect reported by Blakemore et al was measured over a wide range of reference contrasts. As in the previous experiment, the monocular effect was greater than the binocular effect. This occurred at all reference contrasts. These data support the conclusion that the AND channel contributes to visual performance in the same manner, irrespective of stimulus contrast. In the final experiment an alternative explanation for existing evidence against the existence of an AND channel was assessed.

Adult↗
PubMed1989

Subjective contours, tilt aftereffects, and visual cortical organization.

The tilt aftereffect (TAE) was used to study interactions between real and subjective contours. Subjects adapted to either real or illusory lines and were then shown test stimuli containing real or illusory lines. In our first experiment, we found that there is a marked asymmetry in the interactions between real and subjective stimuli. Adaptation to real lines produces comparable TAEs with real and subjective test lines. With either type of test stimulus the maximum effect occurs with a 10-20 deg difference between the orientations of the adaptation and test stimuli. Also, there is a strong TAE when the adaptation and test stimuli contain only subjective lines. However, there is a significantly weaker TAE when the adaptation stimulus is subjective and the test stimulus is real. In a second experiment we find that interocular transfer of tilt aftereffects is greater when the test stimulus is subjective than when it is real. These results are consistent with physiological reports that a subset of orientation selective cells in visual cortex is responsive to subjective contours and that these cells are more binocular, on average, than those responsive only to real contours. Our findings also suggest that the perception of subjective contours is based on the activation of neurons with properties, such as orientation selectivity, which are characteristic of early visual cortical areas.

Adaptation, Ocular↗
PubMed1982

Simultaneous and successive contrast effects in the perception of depth from motion-parallax and stereoscopic information.

Prolonged inspection of a three-dimensional corrugated surface resulted in a successive contrast effect, or aftereffect, of depth, whereby a subsequently-viewed physically-flat test surface appeared to be corrugated in depth with the opposite phase to the adapting surface. The aftereffect occurred both when the depth was specified by motion parallax, in the absence of all other sources of depth information, and when it was specified solely by stereoscopic information. The depth aftereffect was measured by 'nulling' the apparent depth in the test surface with physical relative motion or binocular disparity until the test surface appeared flat. Up to 70% of the depth in the adapting surface was necessary to null the aftereffect. Simultaneous contrast effects in the perception of three-dimensional surfaces were used to investigate the spatial interactions that exist in the processing of motion-parallax and stereoscopic information. A physically vertical surface appeared to slope in depth in the opposite direction to the slope of a surrounding surface. In this case up to 50% of the slope of the inducing surface was necessary to null the contrast effect. Similar results were again obtained for motion-parallax and stereoscopic depth.

Adaptation, Ocular↗
PubMed1983

Aftereffect of induced rotation: separation of inducing and static areas, and monocular component.

The present investigation shows that the aftereffect of induced rotation is observable when there is a large separation of inducing and static areas; it also has a substantial monocular component. These points are consistent with the possible involvement of lateral inhibition in movement detectors. (a) A recent study shows the importance of a peripheral inducing stimulus, and therefore presumably peripheral movement detectors; other psychophysical evidence shows that such detectors have large receptive fields and inhibitory surrounds. (b) Other effects probably involving lateral inhibition in movement detectors have a large monocular component.

Adult↗
PubMed1988

The effects of sustained vertical gaze deviation on the resting state of the vergence system.

Vergence of the eyes in the dark depends on the vertical direction of gaze. In three experiments this phenomenon was studied using eye inclinations and head tilts of 5 min duration during which monocular or binocular near and distant stimuli were inspected. The effects of eye inclination and head tilt on dark vergence were temporally stable; they exhibited even a tendency to increase with the passage of time. On return to horizontal gaze, positive aftereffects were found, that is dark vergence was biased towards its value with a vertically deviated gaze. The effect of vertical gaze direction turned out to be additive to the effect of binocular near fixation. These findings represent evidence against the hypothesis that the effect of vertical gaze direction on dark vergence is mediated by a feedforward signal that is related to voluntary effort in raising or depressing the eyes.

Adaptation, Ocular↗
PubMed1987

Aftereffect of induced rotation: number of pattern elements and area of pattern in inducing stimulus.

Previous research has suggested that aftereffect of induced rotation can be longer when the number of pattern elements in the inducing stimulus is greater. This was explained by the amount of shearing between pattern elements of inducing and static stimuli. However, the results might also be explained by the greater area occupied by a greater number of pattern elements. The present experiment used three inducing stimuli, in which number of pattern elements and area of pattern were varied independently, to test between these hypotheses. The former was corroborated and the latter refuted.

Adult↗
PubMed1993

[Motion aftereffect in analysis of the visual system].

In several experiments the motion after-effect as elicited by spirals and gratings ("waterfall displays") is used to analyze the processing of information within the visual system. The duration and judged strength of after-effects are determined with respect to different fixation conditions (monocular and binocular fixation conditions as well as centric and eccentric fixation). The results show, that motion after-effects in spirals and waterfall displays are generated and processed in different ways within the visual system. The results are discussed on the basis of a metric of the visual system by means of the motion after-effect.

Adult↗
PubMed1987

Possible neural substrates for orientation analysis and perception.

Recent research into the response properties of extrastriate visual cortical mechanisms has revealed single-cell functional organisation which closely parallels certain global and apparently emergent properties of psychophysical observation. An attempt is made to relate previous data on orientation illusions and aftereffects to these extrastriate mechanisms and new data which cannot be explained adequately by V1 (striate) orientation channels are discussed. Conversely, properties of cells in areas such as V3, V4, MT, and others seem to provide an obvious neural substrate for global interactions. It is suggested that psychological 'explanations' couched in terms of 'hypotheses' or 'cognitive problem solving' lack heuristic value, and that, in contrast, the properties of extrastriate cells can suggest novel experimental psychophysical paradigms which are designed to probe these higher-order global mechanisms more or less selectively.

Animals↗
PubMed2006

Eye movements cannot explain vibration-induced visual motion and motion aftereffect.

Eye movements are thought to account for a number of visual motion illusions involving stationary objects presented against a featureless background or apparent motion of the whole visual field. We tested two different versions of the eye movement account: (a) the retinal slip explanation and (b) the nystagmus-suppression explanation, in particular their ability to account for visual motion experienced during vibration of the neck muscles, and for the visual motion aftereffect following vibration. We vibrated the neck (ventral sternocleidomastoid muscles, bilaterally, or right dorsal muscles) and measured eye movements in conjunction with perceived illusory displacement of an LED presented in complete darkness (N=10). To test the retinal-slip explanation, we compared the direction of slow eye movements to the direction of illusory motion of the visual target. To test the suppression explanation, we estimated the direction of suppressed slow-phase eye movements and compared it to the direction of illusory motion. Two main findings show that neither actual nor suppressed eye movements cause the illusory motion and motion aftereffect. Firstly, eye movements do not reverse direction when the illusory motion reverses after vibration stops. Secondly, there are large individual differences with regards to the direction of eye movements in observers who all experience a similar visual illusion. We conclude that, rather than eye movements, a more global spatial constancy mechanism that takes into account head movement is responsible for the illusion. The results also argue against the notion of a single central signal that determines both perceptual experience and oculomotor behaviour.

Adult↗
PubMed2006

Long-lasting aftereffect of a single prism adaptation: shifts in vision and proprioception are independent.

After a single adaptation session to prisms with gradually incremented shift magnitude, the prism adaptation aftereffect was measured by open loop mid-sagittal pointing (O) to a visual target without visual feedback. This aftereffect corresponded to the summation of the shift in proprioception, measured by straight ahead pointing without vision (S), and the visual straight ahead judgement (V), measured by verbal stopping of an LED moving from two opposite directions. However, the measurement of the aftereffects made over a period of 7 days revealed significantly different decay curves in V, O and S. Surprisingly the S shift was still present up to 7 days after the training, while V had returned to the original level by 2 h, which was the first measurement after subjects returned to a normal visual environment. O had returned to pre-test level after 1 day. After 3 days Wilkinson's (J Exp Psychol 89:250-257, 1971) additive hypothesis (O=S-V) no longer fit the data. Rather "O=Pl-V", where Pl (Pr) is the shift in proprioception measured by passive lateral arm movements from left (right), fitted better during the whole 7 days of aftereffect in our study. Therefore, the aftereffect of our strong prism adaptation revealed, firstly, that classical open loop pointing consisted of aftereffect shifts equal to the summation of the shifts in the two passively measurable aftereffect components, vision (V) and proprioception (Pl), rather than with active straight ahead pointing (S). Secondly, the decay of the shift in visual perception and in passively measurable proprioception is independent. The former decays fast, and the latter decays slowly with two separate waves. Thirdly, we suggest that the use of visual perception-dependent spatial codes for visual-manual transformation and the vision-independent internal egocentric reference frame are mutually exclusive. We proposed a model to explain these possible mechanisms.

Adaptation, Physiological↗
PubMed1994

Properties of the stereoscopic (cyclopean) motion aftereffect.

Across four experiments, this study investigated properties of the stereoscopic motion aftereffect (adaptation from moving retinal disparity information). The results showed that stereoscopic motion can induce an adaptation aftereffect across a wide range of conditions and observers, provided that the duration of adaptation is sufficiently long and a perceptually salient test pattern is viewed. Motion adaptation was found to transfer between the stereoscopic and luminance domains [replicating a previous report by Fox, Patterson and Lehmkuhle (1982) Investigative Ophthalmology and Visual Science (Suppl.), 22, 144], suggesting that motion perception from stereoscopic (second-order) and luminance (first-order) attributes is mediated by a common neural substrate.

Adaptation, Ocular↗
PubMed1982

Moon illusion and spiral aftereffect: illusions due to the loom-zoom system?

The moon illusion and the spiral aftereffect are illusions in which apparent size and apparent distance vary inversely. Because this relationship is exactly opposite to that predicted by the static size--distance invariance hypothesis, the illusions have been called "paradoxical." The illusions may be understood as products of a loom-zoom system, a hypothetical visual subsystem that, in its normal operation, acts according to its structural constraint, the constancy axiom, to produce perceptions that satisfy the constraints of stimulation, the kinetic size--distance invariance hypothesis. When stimulated by its characteristic stimulus of symmetrical expansion or contraction, the loom-zoom system produces the perception of a rigid object moving in depth. If this system is stimulated by a rotating spiral, a negative motion-aftereffect is produced when rotation ceases. If fixation is then shifted to a fixed-sized disc, the aftereffect process alters perceived distance and the loom-zoom system alters perceived size such that the disc appears to expand and approach or to contract and recede, depending on the direction of rotation of the spiral. If the loom-zoom system is stimulated by a moon-terrain configuration, the equidistance tendency produces a foreshortened perceived distance for the moon as an inverse function of elevation and acts in conjunction with the loom-zoom system to produce the increased perceived size of the moon.

Astronomical Phenomena↗
PubMed1991

Tilt aftereffect reveals early visual processing deficits in Parkinson's disease and in chronic schizophrenic patients on depot neuroleptic.

Previous studies suggest that the tilt aftereffect (TAE) may be used to indicate the site of dopaminergic abnormalities in the human visual system. In this study we investigated the TAE in patients with Parkinson's disease, and in chronic schizophrenic patients receiving depot injections of neuroleptic. The results suggest that the retina may be abnormal in both groups of patients, and that schizophrenic patients may also have cortical changes. The results are discussed in terms of the clinical implications of these visual changes.

Adult↗
PubMed1996

Visual learning in the perception of texture: simple and contingent aftereffects of texture density.

Novel results elucidating the magnitude, binocularity and retinotopicity of aftereffects of visual texture density adaptation are reported as is a new contingent aftereffect of texture density which suggests that the perception of visual texture density is quite malleable. Texture aftereffects contingent upon orientation, color and temporal sequence are discussed. A fourth effect is demonstrated in which auditory contingencies are shown to produce a different kind of visual distortion. The merits and limitations of error-correction and classical conditioning theories of contingent adaptation are reviewed. It is argued that a third kind of theory which emphasizes coding efficiency and informational considerations merits close attention. It is proposed that malleability in the registration of texture information can be understood as part of the functional adaptability of perception.

Adaptation, Physiological↗