Motion adaptation from surrounding stimuli.

When a narrow uniform gap was surrounded by a moving grating, the gap appeared as a grating in the opposite phase to that of the surround, moving in the same direction with the same speed. Contrast thresholds for moving test-gratings placed in the region of the uniform gap were found to be elevated after prolonged viewing of this pattern, thus demonstrating the existence of motion adaptation in a retinal region surrounded by, but not covered by, a moving pattern. The amplitude of the moving induced-grating was measured by nulling with a real grating moving in the same direction and with the same speed as the surround. When the speed of the inducing grating was varied, the amplitude of the induced effect did not correlate with the magnitude of the threshold elevation. Therefore, it is unlikely that motion adaptation in the uniform gap was due to induced gratings. In some conditions, the adaptation effect of surrounding gratings was no less than the adaptation effect of gratings covering the test region. This result rules out an explantation involving scattered light, and indicates that motion adaptation occurs at a later stage than that consisting of simple motion mechanisms which confound the contrast and velocity of a moving stimulus.     

Absence of color selectivity in the visual movement aftereffect

Lovegrove, Over, and Broerse (1972) reported that the magnitude of the movement aftereffect was reduced when the colors of the inducing and test stimuli differed, relative to when they were the same. Since this result is contrary to some earlier findings, four experiments were conducted to examine this claim. Neither the duration nor the magnitude (as measured by manual tracking) of the aftereffect generated by rotary or linear movement of contours were found to be affected by the color combinations of the inducing and stationary patterns.     

Induced movement as nonveridical resolution of displacement ambiguity: Effect of enclosure and number of field elements

Four experiments on induced movement and induced stationariness are described. Experiments 1 and 2 showed that mere enclosure of a stationary spot in a moving frame does not necessarily result in induced movement. Nor does enclosure of a moving spot in a stationary frame necessarily result in perceived real movement of the spot. Duncker’s principles of enclosure is thus called into question. Two further experiments showed that both induced and perceived real movement of a spot are much more frequent when the frame is replaced by either two or more similar spots which enclose or flank the target spot. It can be concluded that the principle of enclosure obtains when the reference field consists of more than one element which move or remain stationary together. When such a field moves, it is the single, enclosed element which appears to move while the field itself appears stationary.     

Dichoptic induction of movement aftereffects contingent on color and on orientation

Some comparative experiments on the dichoptic induction of the movement aftereffect (MAE) contingent on color and the MAE contingent on orientation are reported. Colorcontingent movement aftereffects could be evoked only when the eye which had viewed color during adaptation also viewed color during test sessions. When the apparent color of the test field was changed by binocular color rivalry, contingent movement aftereffects (CMAEs) appropriate to the suppressed color were reported. After dichoptic induction of the orientation-contingent MAE, aftereffects could be obtained whether the eliciting gratings and stationary test fields were presented together to either eye alone or were dichoptically viewed.     

Spatial-frequency-contingent color aftereffects: Adaptation with one-dimensional stimuli

The McCollough effect was shown to be spatial-frequency selective by Lovegrove and Over (1972) after adaptation with vertical colored square-wave gratings separated by 1 octave. Adaptation with slide-presented red and green vertical square-wave gratings separated by 1 octave failed to produce contingent color aftereffects (CAEs).However, when each of these gratings was adapted alone, strong CAEs were produced. Adaptation with vertical colored sine-wave gratings separated by 1 octave also failed to produce CAEs, but strong effects were produced by adaptation with each grating alone. By varying the spatial frequency of the test sine wave, CAEs were found to be tuned for spatial frequency at 2.85 octaves after adaptation of 4 cycles per degree (cpd) and at 2.30 octaves after adaptation of 8 cpd. Adaptation of both vertical and horizontal sine-wave gratings produced strong CAEs, with bandwidths ranging from 1.96 to 2.90 octaves and with lower adapting contrast producing weaker CAEs. These results indicate that the McCollough effect is more broadly tuned for spatial frequency than are simple adaptation effects.     

Spatial-frequency-contingent color aftereffects: adaptation with one-dimensional stimuli.

The McCollough effect was shown to be spatial-frequency selective by Lovegrove and Over (1972) after adaptation with vertical colored square-wave gratings separated by 1 octave. Adaptation with slide-presented red and green vertical square-wave gratings separated by 1 octave failed to produce contingent color aftereffects (CAEs). However, when each of these gratings was adapted alone, strong CAEs were produced. Adaptation with vertical colored sine-wave gratings separated by 1 octave also failed to produce CAEs, but strong effects were produced by adaptation with each grating alone. By varying the spatial frequency of the test sine wave, CAEs were found to be tuned for spatial frequency at 2.85 octaves after adaptation of 4 cycles per degree (cpd) and at 2.30 octaves after adaptation of 8 cpd. Adaptation of both vertical and horizontal sine-wave gratings produced strong CAEs, with bandwidths ranging from 1.96 to 2.90 octaves and with lower adapting contrast producing weaker CAEs. These results indicate that the McCollough effect is more broadly tuned for spatial frequency than are simple adaptation effects.     

初级视觉皮层在注意振荡中的作用

注意离散性是注意间歇性地采集外界信息的特性, 这种特性在行为中的表现被称为注意振荡。尽管有研究使用经典的线索靶子范式和视觉搜索范式发现行为数据中存在注意振荡, 证明了注意是离散的, 但其相应的神经机制, 即注意离散性与哪些脑区有关, 尚不明确。研究采用高时间分辨率的线索靶子范式和双眼分视技术, 基于人眼视觉通路的解剖学特性, 比较了线索靶子出现在双眼(实验1)、同眼和异眼(实验2)条件下的注意振荡, 考察初级视觉皮层对注意振荡的影响。结果发现：1)双眼分视会对注意振荡发生的频段产生影响, 非双眼分视条件下, 注意振荡出现在低频(2 Hz和8 Hz)。而双眼分视条件下, 注意振荡则出现在更高的频段(12.5 Hz)。2)无论线索靶子出现在同眼还是异眼, 注意振荡的频段无显著差异。结果表明V1区双眼视觉通路或者更高级的视觉区可能参与注意振荡, 为探明注意振荡的神经机制提供了重要的行为学证据。     

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.     

Simultaneous visual events show a long-range spatial interaction

A stimulus consisting of two brief flashes separated by a short interval appears to flicker, whereas a single brief flash does not. Performance on a task requiring discrimination of double and single stimuli is adversely affected by simultaneous presentation of a second, similar stimulus at a relatively remote position in the visual field. Most errors occur when target and mask follow different time courses, one double and the other single. The results of four experiments studying this interaction are reported. An effect on performance is observed under binocular, monocular, and dichoptic viewing conditions. Performance is affected up to target to mask distances of at least 20 deg of arc. Performance increases as target-to-mask onset asynchrony is increased, reaching asymptote at asynchronies of between 100 and 150 msec. The precise shape of the stimuli does not appear to be important in determining the size of the effect or whether or not an effect occurs. An analogy between this effect and apparent movement is suggested.     

Induced subject-relative movement: Persistence of apparent movement of a stationary point after removal of inducing stimulus

It was observed by chance that perceived movement of a stationary spot of light in a dark featureless field persists after its induced movement by a moving frame. When the frame was suddenly occluded, apparent movement of the spot persisted in the same direction as prior induced movement. The effect which is compelling and readily reported and referred to as induced subject-relative movement (ISRM) was confirmed and further investigated in four experiments. In the first, the informal observations of ISRM were confirmed using manual tracking to index perceived movement, and in the second, it was shown to occur only very slightly and briefly when the frame merely stopped. In the third experiment, ISRM was shown to occur following two different paths of induced movement, and in the fourth, not to occur following real movement of the spot, which was almost indistinguishable from its induced movement. It is suggested that the effect arises from the absence of a signal for cessation of perceived movement when the frame disappears.     

Movement aftereffects contingent on color,intensity, and pattern

We have found contingent movement aftereffects (CMAEs) lasting several days, contingent upon the color, intensity, and stripe width of moving patterns. Ss adapted for 10 min to a patterned disk rotating clockwise under red light, alternating every 10 sec with counterclockwise under green light. When stopped, the disk then appeared to rotate counterclockwise under red light and clockwise under green light. The effect lasted only a second or two, reappearing each time the field’s color was changed. But it increased in strength over the first 1/2 hand was still present 1 or 2 days later. Color transposition effects were found: after adaptation to red-clockwise (long wavelength) alternating with green-counterclockwise (short wavelength), a stationary yellow (long wavelength) test field appeared to rotate counterclockwise and a blue (short wavelength) field appeared to rotate clockwise. Relative, not absolute, color of the test triggered the CMAE. Similar CMAEs and transposition effects were produced by pairing direction of movement with intensity, with width of moving stripes and with orientation of a stationary grating projected onto a rotating patterned disk.     

Color-luminance relationships and the McCollough effect

The McCollough effect is an orientation-specific color aftereffect induced by adapting to colored gratings. We examined how the McCollough effect depends on the relationships between color and luminance within the inducing and test gratings and compared the aftereffects to the color changes predicted from selective adaptation to different color-luminance combinations. Our results suggest that the important contingency underlying the McCollough effect is between orientation and color-luminance direction and are consistent with sensitivity changes within mechanisms tuned to specific color-luminance directions. Aftereffects are similar in magnitude for adapting color pairs that differ only in S cone excitation or L and M cone excitation, and they have a similar dependence on spatial frequency. In particular, orientation-specific aftereffects are induced for S cone colors even when the grating frequencies are above the S cone resolution limit. Thus, the McCollough effect persists even when different cone classes encode the orientation and color of the gratings.     

Color—luminance relationships and the McCollough effect

The McCollough effect is an orientation-specific color aftereffect induced by adapting to colored gratings. We examined how the McCollough effect depends on the relationships between color and luminance within the inducing and test gratings and compared the aftereffects to the color changes predicted from selective adaptation to different color—luminance combinations. Our results suggest that the important contingency underlying the McCollough effect is between orientation and color—luminance direction and are consistent with sensitivity changes within mechanisms tuned to specific color—luminance directions. Aftereffects are similar in magnitude for adapting color pairs that differ only in S cone excitation or L and M cone excitation, and they have a similar dependence on spatial frequency. In particular, orientation-specific aftereffects are induced for S cone colors even when the grating frequencies are above the S cone resolution limit. Thus, the McCollough effect persists even when different cone classes encode the orientation and color of the gratings.     

Outflow and inflow in movement duplication

Following prolonged exposure to two vertical grating patterns differing in spatial frequency—one pattern illuminated in green light alternated with the other pattern illuminated in red light—human observers will sometimes report seeing desaturated complementary colors when presented with a neutrally illuminated test field consisting of adjacent halves of the two adapting gratings. The number of such color reports increases as the difference between the spatial frequencies of the adapting gratings increases. This frequency-specific chromatic aftereffect is similar to that obtained with orientation-specific color adaptation and may be mediated by neural “channels,” sensitive to both color and frequency input, which are similar to units known to exist in the visual systems of lower organisms.     

Determinants of fusion of dichoptically presented orthogonal gratings

Liu, Tyler, and Schor (1992 Vision Research 32 1471-1479) reported the surprising finding that dichoptically presented orthogonal sine-wave gratings do not always produce binocular rivalry. Gratings of high spatial frequency, and especially of low contrast, fuse to produce a stable percept of a dichoptic plaid. Using a somewhat different perceptual task, we replicated those findings and extended them. The probability of a plaid percept is higher for square-wave gratings than for sine-wave gratings, and higher still for rectangular-wave gratings with high duty cycles (with very thin light or dark bars). Experiments were conducted to test whether this duty-cycle effect was due to changes in overall luminance, or in the size of the regions of luminance congruity (which may reduce the probability of rivalry), but no such effects could account for the results. The presence of locally conflicting contour information in the two eyes was shown to be an important determinant of rivalry onset, but, since removing such regions did not eliminate rivalry, other factors also have a role to play. The spatial frequency composition of the gratings is one such factor which is consistent with all of the findings we report.     

Visual stimuli for strabismic suppression

The effects of orientation and spatial frequency of grating stimuli upon suppression were examined with a binocular rivalry paradigm in a group of ten strabismic patients and in a control normal group. Duration, frequency, and period of rivalry were examined as functions of differences in orientation and spatial frequency of dichoptic achromatic sinusoidal gratings. Records were made of responses by the sighting and by the nonsighting eye as well as responses during periods of combined binocular vision. Strabismic subjects reported normal binocular rivalry when presented with gratings of dissimilar orientation. Suppression of the deviating eye in strabismic subjects occurred with stimuli of similar orientation and was unaffected by spatial-frequency differences between dichoptic stimuli. Suppression was most intense under conditions that normally stimulate stereopsis and sensory fusion.     

Induced rotation with concentric patterns

Duncker (1929) described induced rotation of a radial-line pattern when a concentric, enclosing annulus pattern rotated. This observation has not, so far, been confirmed or extended. Six experiments are described. The results from Experiments 1 and 2 showed that the frequency with which induced rotation is reported during standard observation periods is not affected by either angular velocity up to 15 deg/sec or unpatterned gaps up to 5 deg wide between the inner and outer patterns. Experiment 3 confirmed that the strength of the effect can be satisfactorily measured by cancellation of induced movement. Experiments 4–6 showed that induced rotation is very weak or absent when the inner disk rotates and the concentric annulus is stationary, increases in velocity as the number of radial lines in the rotating annulus increases by up to half the number in the stationary disk, and is only slightly stronger when the area of contrast between moving and stationary lines is poorly resolved in the peripheral visual field. The results are considered in terms of the resolution in perception of displacement ambiguity between moving and stationary elements.     

Brightness selectivity in the motion aftereffect

Eighteen Ss were required to track the apparent motion of a stationary grating viewed after prolonged inspection of a moving grating. Measures were obtained with the inspection and test gratings identical in contrast but different in space-average luminance, or with luminance held constant and contrast varied. The aftereffect was reduced as the gratings differed in space-average luminance, but contrast exerted less uniform influence as a variable. Brightness-selectivity in the motion aftereffect is interpreted within the selective adaptation model of aftereffects as evidence that some detectors in human vision are conjointly tuned to space-average luminance and image motion.     

Perceptual integration of motion and form information: evidence of parallel-continuous processing

In three visual search experiments, the processes involved in the efficient detection of motion-form conjunction targets were investigated. Experiment 1 was designed to estimate the relative contributions of stationary and moving nontargets to the search rate. Search rates were primarily determined by the number of moving nontargets; stationary nontargets sharing the target form also exerted a significant effect, but this was only about half as strong as that of moving nontargets; stationary nontargets not sharing the target form had little influence. In Experiments 2 and 3, the effects of display factors influencing the visual (form) quality of moving items (movement speed and item size) were examined. Increasing the speed of the moving items (> 1.5 degrees/sec) facilitated target detection when the task required segregation of the moving from the stationary items. When no segregation was necessary, increasing the movement speed impaired performance: With large display items, motion speed had little effect on target detection, but with small items, search efficiency declined when items moved faster than 1.5 degrees/sec. This pattern indicates that moving nontargets exert a strong effect on the search rate (Experiment 1) because of the loss of visual quality for moving items above a certain movement speed. A parallel-continuous processing account of motion-form conjunction search is proposed, which combines aspects of Guided Search (Wolfe, 1994) and attentional engagement theory (Duncan & Humphreys, 1989).     

The effect of moving and static trans-scleral illumination of visual afterimages

The inside of the eye was illuminated by shining a small light through the upper eyelid and the sclera. After viewing a bright light flash, Ss closed their eyes and reported the duration of the afterimage under the following conditions: the light on and moving across the S’s eyelid (moving trans-scleral illumination), the light on but stationary (static trans-scleral illumination), and two corresponding control conditions in which the light was turned off (darkness). Results indicate that when the trans-scleral light is moving, afterimages are seen clearly for periods of approximately the same duration as those seen in complete darkness. However, when the trans-scleral illumination is stationary, the duration of the afterimages is significantly reduced. These results are compatible with other afterimage data that suggest that changes within the field after initial stimulation are needed to prolong afterimages.