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Biomedical subjects

N J Wade

Publications and source records attributed to N J Wade.

At least 19 recordsLinked to original sources
PubMed1992

Motion over the retina and the motion aftereffect.

The motion aftereffect (MAE) was measured with retinally moving vertical gratings positioned above and below (flanking) a retinally stationary central grating (experiments 1 and 2). Motion over the retina was produced by leftward motion of the flanking gratings relative to the stationary eyes, and by rightward eye or head movements tracking the moving (but retinally stationary) central grating relative to the stationary (but retinally moving) surround gratings. In experiment 1 the motion occurred within a fixed boundary on the screen, and oppositely directed MAEs were produced in the central and flanking gratings with static fixation; but with eye or head tracking MAEs were reported only in the central grating. In experiment 2 motion over the retina was equated for the static and tracking conditions by moving blocks of grating without any dynamic occlusion and disclosure at the boundaries. Both conditions yielded equivalent leftward MAEs of the central grating in the same direction as the prior flanking motion, ie an MAE was consistently produced in the region that had remained retinally stationary. No MAE was recorded in the flanking gratings, even though they moved over the retina during adaptation. When just two gratings were presented, MAEs were produced in both, but in opposite directions (experiments 3 and 4). It is concluded that the MAE is a consequence of adapting signals for the relative motion between elements of a display.

Attention↗
PubMed1992

The interaction of perceived distance with the perceived direction of visual motion during movements of the eyes and the head.

A horizontally moving target was followed by rotation of the eyes alone or by a lateral movement of the head. These movements resulted in the retinal displacement of a vertically moving target from its perceived path, the amplitude of which was determined by the phase and amplitude of the object motion and of the eye or head movements. In two experiments, we tested the prediction from our model of spatial motion (Swanston, Wade, & Day, 1987) that perceived distance interacts with compensation for head movements, but not with compensation for eye movements with respect to a stationary head. In both experiments, when the vertically moving target was seen at a distance different from its physical distance, its perceived path was displaced relative to that seen when there was no error in perceived distance, or when it was pursued by eye movements alone. In a third experiment, simultaneous measurements of eye and head position during lateral head movements showed that errors in fixation were not sufficient to require modification of the retinal paths determined by the geometry of the observation conditions in Experiments 1 and 2.

Adult↗
PubMed1991

Induced rotary motion and ocular torsion.

When a large patterned annulus rotates around a stationary sectored disc the latter appears to rotate in the opposite direction. Such induced rotary motion was examined with central discs subtending 5, 20 and 40 deg at the eye, with the surround filling the remainder of the visual field. The annular surround or the central disc could be oscillated sinusoidally around the fixation point through 20 deg at 0.2 Hz. In each case, subjects estimated the angles through which the moving and stationary parts of the display appeared to rotate on one half-cycle. Subjects also estimated the angle of rotation of an oscillating display that filled the visual field. Induced rotation of the centre was around 100% of the inducing amplitude for all disc sizes, but there was no induced motion of the surround when the centre rotated. Ocular torsion was measured under the same conditions, using the scleral search-coil technique. The amplitude of ocular torsion was a function of the size of the stationary or rotating field. Thus, variations in stimulus conditions affected induced rotary motion and ocular torsion in different ways. The implications of the results for theories of induced motion in terms of underregistered eye movements are discussed.

Eye Movements↗
PubMed1990

A balanced view of otolithic function: comment on Stoffregen and Riccio (1988)

Stoffregen and Riccio (1988) have presented a theory of orientation that dismisses the role of otolithic information in the perception of the direction of the gravitoinertial force (GIF). Their dismissal of otolithic involvement in GIF perception is not warranted because (a) the logic associated with their analysis is flawed. (b) the underwater experiments they analyzed do not reflect the isolated operation of otolithic function, and (c) they do not cite a large body of relevant evidence on otolithic function.

Gravitation↗
PubMed1990

The binocular representation of uniform motion.

In the model of motion perception proposed by Swanston, Wade, and Day (1987, Perception 16 143-159) it was suggested that retinocentric motion and eye movement information are combined independently for each eye, to give left and right orbitocentric representations of movement. The weighted orbitocentric values are then added, to give a single agocentric representation. It is shown that for a physical motion observed without pursuit eye movements this formulation predicts a reduction in the perceived extent of motion with monocular as opposed to binocular viewing. This prediction was tested, and shown to be incorrect. Accordingly, a modification of the model is proposed, in which the left and right retinocentric signals are weighted according to the presence or absence of stimulation, and combined to give a binocular retinocentric representation. In a similar way left-eye and right-eye position signals are combined to give a single binocular eye movement signal for version. This is then added to the binocular retinocentric signal to give the egocentric representation. This modification provides a unified account of both static visual direction and movement perception.

Attention↗
PubMed1988

Compound binocular rivalry.

Binocular rivalry was examined with random dot patterns consisting of three colours: red, green and grey. The microstructure of the patterns was defined by the individual dots, and the correspondence between the microstructures in the two eyes was manipulated. The macrostructures were defined by the distributions of red, green and grey dots over the displays, so that they consisted of orthogonally striped patterns. The degree of correspondence between the microstructures was varied in Expt 1, together with the spatial frequency of the microstructure. Rivalry periods of the macrostructures were briefer when the microstructures were in correspondence, In Expt 2 the spatial frequencies of the macrostructures were varied. The lower spatial frequency predominated for longer than the higher. The results are discussed in terms of independent pathways for corresponding and rivalry stimulation. In addition a stimulus pairing that produces clear dichoptic colour mixtures is presented.

Dominance, Cerebral↗
PubMed1987

The effect of orientation and motion of enclosed texture on induced movement.

Optical expansion or contraction of a vertical grating induces rotation of an oblique line or bar superimposed upon it. Three experiments are reported in which the oblique (45 deg clockwise) bar was defined by parallel line segments that were varied in orientation and motion. In Experiment 1 subjects estimated the degrees through which the boundaries of the bar appeared to rotate during 2 sec expansion of the vertical grating background. The induced rotation declined with increasing relative orientation between the texture elements and the background; virtually no effect was reported when they were orthogonal. The texture elements were stationary in Experiment 1 whereas they expanded or contracted in Experiment 2: when their motion was in-phase with the background induced rotation of the boundary occurred irrespective of relative orientation. Expansion or contraction of the texture elements alone did not result in induced bar rotation (Experiment 3). It was concluded that induced movement at the boundaries between two patterns is reduced when they differ in static orientation and in the directions of motion due to zooming.

Form Perception↗
PubMed1987

The representation of uniform motion in vision.

For veridical detection of object motion any moving detecting system must allocate motion appropriately between itself and objects in space. A model for such allocation is developed for simplified situations (points of light in uniform motion in a frontoparallel plane). It is proposed that motion of objects is registered and represented successively at four levels within frames of reference that are defined by the detectors themselves or by their movements. The four levels are referred to as retinocentric, orbitocentric, egocentric, and geocentric. Thus the retinocentric signal is combined with that for eye rotation to give an orbitocentric signal, and the left and right orbitocentric signals are combined to give an egocentric representation. Up to the egocentric level, motion representation is angular rather than three-dimensional. The egocentric signal is combined with signals for head and body movement and for egocentric distance to give a geocentric representation. It is argued that although motion perception is always geocentric, relevant registrations also occur at the three earlier levels. The model is applied to various veridical and nonveridical motion phenomena.

Concept Formation↗
PubMed1987

The representation of nonuniform motion: induced movement.

Induced motion occurs when there is a misallocation of nonuniform motion. Theories of induced motion are reviewed with respect to the model for uniform motion recently proposed by Swanston, Wade, and Day. Theories based on single processes operating at one of the retinocentric, orbitocentric, egocentric, or geocentric levels are not able to account for all aspects of the phenomenon. It is therefore suggested that induced motion is a consequence of combining two different types of motion signals: one provides information by registering the motion with respect to the retina, orbit, and egocentre; the other provides information only on the relational motions between the pattern elements. Simple rules are given for defining a frame of reference for the relational motion process, which can result in a reallocation of the motion signals. It is proposed that the two signals in combination are weighted differentially, with the greater influence coming from the relational signals. Procedures for determining the weighting factors are described, and predictions from the model are examined.

Eye Movements↗
PubMed1987

On the late invention of the stereoscope.

It was not until 1838, when Wheatstone published his account of the stereoscope, that stereoscopic depth perception entered into the body of binocular phenomena. It is argued that the stereoscope was not invented earlier because the phenomenon of stereopsis based on disparity had not been adequately described. This was the case despite the fact that there had been earlier descriptions of tasks that could be performed better with two eyes than with one; the perceptual deficits attendant upon the loss of one eye had been remarked upon; analyses of the projections to each eye were commonplace, and binocular disparities were accurately illustrated; moreover, binocular microscopes and telescopes had been made over a century earlier. Theories of binocular vision were generally confined to accounting for singleness of vision with two eyes, and the concepts employed to account for this were visible direction, corresponding retinal points, and union in the brain. The application of these concepts inhibited any consideration of disparities, other than for yielding diplopia. When perception of the third dimension was addressed by Berkeley at the beginning of the eighteenth century, it was in the context of monocular vision and binocular convergence. Thereafter visual direction became the province for binocular vision and it was analysed in terms of geometrical optics, whereas visual distance was examined in the context of learned associations between vision and touch. This artificial division was challenged initially with respect to visual direction and later with respect to stereopsis. An additional factor delaying the invention of the stereoscope was that experiments on binocular vision generally involved abnormal convergence on extended objects. Wheatstone's accidental observation of stereopsis was under artificial conditions in which disparity alone defined the binocular depth perceived. Once invented the stereoscope was enthusiastically embraced by students of vision. It is suggested that the ease with which retinal disparity could be manipulated in stereopairs has led to an exaggeration of its importance in space perception. "The appearances, which are by this simple instrument rendered so obvious, may be easily inferred from the established laws of perspective; for the same object in relief is, when viewed by a different eye, seen from the two points of sight at a distance from each other equal to the line joining the two eyes. Yet they seem to have escaped the attention of every philosopher and artist who has treated of the subjects of vision and perspective." (Wheatstone 1838, page 371).

Depth Perception↗
PubMed1986

Aftereffects in binocular rivalry.

Five experiments are reported in which the aftereffect paradigm was applied to binocular rivalry. In the first three experiments rivalry was between a vertical grating presented to the left eye and a horizontal grating presented to the right eye. In the fourth experiment the rivalry stimuli consisted of a rotating sectored disc presented to the left eye and a static concentric circular pattern presented to the right. In experiment 5 rivalry was between static radiating and circular patterns. The predominance durations were systematically influenced by direct (same eye) and indirect (interocular) adaptation in a manner similar to that seen for spatial aftereffects. Binocular adaptation produced an aftereffect that was significantly smaller than the direct aftereffect, but not significantly different from the indirect one. A model is developed to account for the results; it involves two levels of binocular interaction in addition to monocular channels. It is suggested that the site of spatial aftereffects is the same as that for binocular rivalry, rather than sequentially prior.

Adaptation, Ocular↗
PubMed1986

Binocular rivalry with rotary and radial motions.

Binocular rivalry between a radially sectored and a concentrically circular pattern was investigated in three experiments. Motion of the circular pattern was either cyclical expansion and contraction with corresponding changes in spatial frequency (experiment 1), or outward motion with a constant linear velocity (experiment 2). When both patterns were static the circular pattern was visible for longer than the radial one. Motion of either pattern alone resulted in an increase in the predominance duration and the mean period for which the pattern was visible. This is at variance with Levelt's model of rivalry. In the third experiment, rivalry was between a static circular pattern and a radial pattern that could be rotated at different angular velocities. Again it was found that an increase in stimulus strength, as measured by predominance, led to an increase in the mean periods of visibility of the rotating pattern.

Functional Laterality↗