Biological image motion processing: a review.
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Adult↗
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Results for “FIGURAL AFTEREFFECT”
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Contrast threshold elevation following continuous and interrupted adaptation.
Contrast thresholds for a 6 c/deg sinewave grating were measured following continuous and interrupted adaptation of 10 min duration to a high-contrast (0.6) sinewave grating of the same spatial frequency. Interrupted adaptation was administered as five 2-min segments, and the interadaptation interval (IAI) was varied from 10 to 180 sec. The results indicate that adaptation to spatial contrast can be described by a two-staged process, each stage having a different time constant of adaptation decay.
Adaptation, Ocular↗
Motion after-effects in cat striate cortex elicited by moving texture.
Responses of striate cortical neurons to randomly-textured test patterns (static visual noise), or to bars of optimal orientation and width, moving back-and-forth with fixed velocity, were recorded in the lightly anaesthetized cat. Effects of prior adaptation with textured patterns drifting continuously in each cell's preferred or null directions, were assessed. Alterations of directional bias and responsiveness to the test stimulus were assessed in relation to the degree and time-course of texture adaptation. The effects of adaptation to moving texture were qualitatively similar to our previously published data on adaptation to drifting gratings in the same or similar cells. Responses to the test stimulus were transiently depressed in the direction of adaptation and enhanced following adaptation in the opposite direction, compared with responses following exposure to stationary texture. However, even in cells that were driven strongly by the adapting texture, i.e. particularly the special complex cells in cortical layers III and V, the after-effects were always weak in strength compared with those elicited by moving gratings. We conclude that, as a group, cortical cells strongly sensitive to texture motion are relatively unsusceptible to adaptation.
Action Potentials↗
Recovering motion information from luminance.
We review evidence that visual transient channels responding to temporal change of luminance provide inputs to motion mechanisms, and also play a part in judgments of static brightness. These channels can be adapted to give after effects of apparent dimming or brightening. Nonlinearity in these channels causes a sawtooth grating to look dark (or light) while it is moving to the left (or right). The perceptual outcome in a competitive motion situation is governed by the larger temporal change in luminance: when a white bar and a black bar suddenly change places, on a dark (light) surround it is the white (black) bar that appears to move. The motion system responds to linear, not log luminance. If a black and white picture dissolves (fades) to its own photographic negative which if shifted a few min arc to the right "reversed apparent motion" is seen toward the left. These results constrain possible models of motion perception.
Adaptation, Ocular↗
Simultaneous binocular integration of the visual tilt effect in normal and stereoblind observers.
Apparent displacement of an edge from the subjective visual vertical is typically induced by the simultaneous inspection of a large rotating textured background. In the present series of experiments we have tested the binocular integration of such an effect in normal and stereoblind observers in whom inspection of the rotating background and vision of the vertical edge are presented to different eyes. In normal subjects there was no difference between the binocular and the dichoptic viewing condition while in stereoblind subjects there was a clearcut decrease in the strength of the tilt effect under dichoptic conditions. A residual tilt effect, however, was still present in the latter group under dichoptic conditions and this shows that binocular interactions related to visual tilt can be dissociated from those required for stereopsis.
Adolescent↗
Motion mechanisms have only limited access to form information.
We investigate the roles of spatial frequency content, flicker and higher-order elements of form ("features") in the generation of motion percepts. These cues are separated through the use of dynamic visual stimuli based on stochastic textures. Flicker alone and spatial frequency content alone suffice to generate a strong motion percept, but higher-order elements of form alone generate a much weaker motion percept. Thus, even for achromatic stimuli, all pattern information is not equally available for motion processing. Furthermore, higher-order form information, which by itself does not provide a strong cue to motion, is shown to interact with other visual information to facilitate determination of direction of motion.
Adult↗
Selective nonconjugate binocular adaptation of vertical saccades and pursuits.
Hering's law describes the equal and symmetrical rotation of the two eyes. It is possible to calibrate the binocular yoking of the two eyes in response to disparate size and/or motion of the two ocular images. It is unclear if the ratio of movements by the two eyes is modified by selective adaptation of each versional system (i.e. saccades and pursuits) or if there is an apparent adaptation of Hering's law that results from a single underlying process. The latter could be accomplished by vergence (prism) adaptation, which could interact with all versional systems. In this investigation, binocularly stimulated saccades and pursuits were adapted separately for 2 hr to unequal vertical target displacements. Three adaptation paradigms were used; each included a 10% binocular gradient disparity. The adapting stimulus for the pursuit system was 0.25 Hz vertical triangular motion of 20 deg, peak to peak. Two saccade adaptation paradigms included one which emphasized correcting vertical disparity during the pulse component of the saccade, the other minimized the influence of disparity prior to, during and immediately after saccades (vergence paradigm). Yoking ratios (YRs) for vertical pursuits and saccades were compared before and after adaptation. The pursuit paradigm produced marked adaptation of the pursuit YRs while it had negligible effect on saccade YRs. The pulse saccade paradigm adapted the saccade YRs twice as much as the pursuit YRs whereas the vergence paradigm resulted in little adaptation of YRs for either saccades or pursuits. Pursuits adapted to the first paradigm in 15-30 min whereas saccades adapted to the second paradigm in 1.5-2 hr. These results indicate that there is not a single common nonconjugate adaptation mechanism for vertical pursuits and saccades. Results of the vergence paradigm demonstrate that feedback during or immediately after eye movements is necessary in order to stimulate the binocular versional adaptation mechanism. Versional adaptation may be considered as a calibration of Hering's law.
Adaptation, Ocular↗
Motion of complex patterns is computed from the perceived motions of their components.
A plaid pattern made by adding two gratings of the same spatial frequency, one moving 45 deg above the horizontal, and the other moving 45 deg below the horizontal, appears to move horizontally when the speeds of the two components are equal. If the apparent speed of the upward-moving component is reduced by a motion after-effect (MAE), the plaid appears to move obliquely downwards, unless the actual speed of the downward-moving component is reduced to match the (reduced) apparent speed of the upward moving component. This is consistent with the hypothesis that the visual system computes the motion of a plaid pattern in two stages, first estimating the motions of the components, and then combining them according to the intersection of constraints. An alternative explanation: that the vertical component of the plaid's motion is caused by an MAE in a horizontally oriented distortion product generated by non-linear transduction or transmission of the plaid, is ruled out by the finding that the adapting stimulus causes only a very weak vertical MAE.
Adaptation, Ocular↗
First-order and second-order visual processes in the perception of motion and tilt.
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Adaptation, Ocular↗
Influence of gravitoinertial force level on vestibular and visual velocity storage in yaw and pitch.
Velocity storage is an important aspect of sensory-motor control of body orientation. The effective decay rate and three-dimensional organization of velocity storage are dependent upon body orientation relative to gravity and also are influenced by gravitoinertial force (G) level. Several of the inputs to velocity storage including otolithic, somatosensory, proprioceptive, and possibly motor are highly dependent on G level. To see whether the G dependency of velocity storage is related to changes in the effective coupling of individual sensory inputs to the velocity storage mechanism or to alterations in the time constant of velocity storage per se, we have studied horizontal vestibular nystagmus, horizontal optokinetic after nystagmus (OKAN) and vertical vestibular nystagmus as a function of force level. Horizontal OKAN and vestibular nystagmus both showed no effect of G level on their initial or peak slow phase velocities but their decay rates were quicker in 0G and 1.8G than in 1G. Vertical vestibular nystagmus also showed no effect of G level on peak velocity but decayed quicker in 0G relative to 1G. These-findings indicate that the intrinsic decay rate of a common velocity storage mechanism is affected by the magnitude of G. A negligible amount of slow phase eye velocity was observed in planes outside the planes of stimulation, thus short-term changes in G across multiple body axes can change velocity storage, but the change is restricted to the axis common to the rotary stimulus and the G vector.
Aerospace Medicine↗
Eye movements during motion after-effect.
Using the magnetic search coil technique, we measured torsional eye movements in four male subjects during and after rotation of a visual display around the line of sight. During rotation of the display, subjects developed a torsional nystagmus with slow-phases in the direction of target rotation that had a typical gain of less than 0.01. Upon cessation of display motion, subjects experienced a motion after-effect (MAE) in the direction opposite prior target rotation, which persisted for greater than 15 sec. During this MAE, slow-phase eye movements of low velocity were in the same direction as the MAE, but did not persist as long as perceptual effects. In separate experiments, horizontal eye movements were recorded during horizontal stimulus motion; during MAE, no eye movements occurred due to stronger fixation mechanisms. We conclude that MAE is not caused by retinal slip of images, but MAE and the accompanying eye movements might be produced by shared or similar mechanisms.
Adult↗
Simultaneity in the Ternus configuration: psychophysical data and a computer model.
The Ternus configuration is an apparent motion display which is typically described as being bistable; subjects usually describe seeing either element motion or group motion, depending upon temporal properties of the display. The results of an experiment are reported in which subjects are also permitted to report seeing four stationary display elements (simultaneity). It was found that simultaneity was produced when both frame durations and interstimulus intervals (ISIs) were brief. A weaker than expected effect of stimulus onset asynchrony (SOA) was revealed because this third type of judgment was obtained. Furthermore, statistical analyses indicated that SOA was not by itself the best predictor of judgment type. The interaction between duration and ISI was also an important predictor. This suggested that a complete account of the Ternus configuration requires two mechanisms: a visible persistence mechanism, governed by an SOA law, and a motion correspondence mechanism, governed by an ISI law. These two mechanisms were added to Dawson's (1991) [Psychological Review, 98, 569-603] autoassociative network for motion correspondence processing. The resulting model could generate each of the three interpretations of the Ternus configuration at appropriate combinations of frame duration and ISI.
Association↗
Recovery from motion adaptation is delayed by successively presented orthogonal motion.
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 the test pattern is not immediately or not continuously presented after adaptation. This phenomenon is called storage. So far research indicates that storage only 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-directional motion of a random-pixel array M1 for 60 sec. This stimulus was immediately followed by another moving pattern M2. Its motion direction was orthogonal to that of M1. 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 uni-directional MAE was measured. For short presentation times of M2 there is an integrated uni-directional MAE, which shows an interaction of the output of units stimulated by both moving patterns. However, it appeared that the effect of M1 on the direction of this combined uni-directional MAE is much longer present than would be expected from the MAE duration of M1, when tested in isolation.
Adaptation, Ocular↗
Evoked potential augmenting and reducing: the methodological and theoretical significance of new electrophysiological observations.
Buchsbaum's (1976) evoked potential (EP) procedure reveals differences in the slope of P100-N140 amplitude changes with variation of stimulus luminance. Subjects are classed 'augmenters' or 'reducers', respectively, if their slopes are positive or negative. Psychological correlates of this slope index have been reported and it has distinguished psychiatric patient populations from healthy subjects. Data are presented which indicate that the augmenting-reducing slope differences are due to an early slow-wave. For augmenters, the major slow-wave deflection is of positive polarity. At the highest luminance, with a correspondingly shorter latency, the slow-wave increases the positive-going P100 deflection. At the lowest luminance, with a longer latency, it reduces the negative-going N140 deflection. This results in positive slopes. For reducers, the major slow-wave deflection is of negative polarity. This influences the measured P100 and N140 amplitudes in a manner opposite to that described for augmenters and results in negative slopes. Since these findings provide new insights concerning the nature of the Buchsbaum augmenting-reducing phenomenon, they have methodological and theoretical implications. It is concluded that the Buchsbaum procedure is an effective measure of slow-wave differences but that the reducing effect is difficult to explain in terms of Pavlov's concept of protective inhibition. An alternative 'opponent-process' explanation is offered.
Brain↗
The visual perception of motion.
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Eye Movements↗
Eye movements: building a stable world from glance to glance.
Frequent exploratory eye-movements called saccades pose for the visual system the problem of combining information from successive fixations into an apparently seam less conscious experience. A new study shows that information from successive fixations is combined, not by fusing fixation 'snapshots', but by integrating more complex visual attributes at a mid-high level of analysis.
Consciousness↗
Widespread functional connectivity and fMRI fluctuations in human visual cortex in the absence of visual stimulation.
To what extent does the visual system's activity fluctuate when no sensory stimulation is present? Here, we studied this issue by examining spontaneous fluctuations in BOLD signal in the human visual system, while subjects were placed in complete darkness. Our results reveal widespread slow fluctuations during such rest periods. In contrast to stimulus-driven activity, during darkness, functionally distinct object areas were fluctuating in unison. These fMRI fluctuations became rapidly spatially de-correlated (39% drop in correlation level, P < 0.008) during visual stimulation. Functional connectivity analysis revealed that the slow spontaneous fluctuations during rest had consistent and specific neuro-anatomical distribution which argued against purely hemodynamic noise sources. Control experiments ruled out eye closure, low luminance and mental imagery as the underlying sources of the spontaneous fluctuations. These results demonstrate that, when no stimulus is present, sensory systems manifest a robust level of slow organized fluctuation patterns.
Adult↗
Object-based cross-feature attentional modulation from color to motion.
Object-based theories of visual attention predict that attempting to direct attention to a particular attribute of a visual object will result in an automatic selection of the whole object, including all of its features. It has been assumed, but not critically tested, that the spreading of attention from one feature to another in this manner, i.e. cross-feature attentional (CFA) effects, takes place at object-level stages of processing as opposed to early, local stages. In the present study we disambiguated these options for color-to-motion CFA by contrasting attention's effect on bivectorial transparent versus bivectorial locally paired motion displays. We found that association between features at the global, but not at the local, stage of motion processing leads to cross-feature attentional effects. These findings provide strong psychophysical evidence that such effects are indeed object-based.
Adaptation, Physiological↗