[Some effects produced by radial accelerations of different significance at the visual-motor level].
Explore the source record for details and available documents.
Acceleration↗
SEARCH · Search PubMed
Results for “Motion Perception”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
THRESHOLDS FOR THE PRECEPTION OF LINEARLY INCREASING ANGULAR ACCELERATIONS.
Explore the source record for details and available documents.
Acceleration↗
[PERCEIVED RATE AND THE V EQUALS E/T RATIO].
Explore the source record for details and available documents.
Biophysical Phenomena↗
Role of motion integration in contour perception.
Contours are believed to play a key role in the visual analysis of scenes by the primate brain. In dynamic scenes, the presence of contours is often signaled by discontinuities in motion fields. However, it is unclear whether the motion fields over which the visual system extracts discontinuities, correspond to the local optic-flow or the pattern motion fields obtained by integrating local estimates. A resolution of this issue would provide important clues about the organization of visual motion and form analysis processes. In this paper, we present experimental evidence which suggests that the perception of motion defined contours is strongly dependent on motion integration - an operation that is believed to take place relatively late in the visual stream.
Form Perception↗
Multi-directional shifts of optokinetic responses to binocular-rivalrous motion stimuli.
Previous dichoptic experiments showed that dissimilar stationary pattern stimuli resulted in the perception of binocular rivalry, whereas oppositely-directly moving grating stimuli resulted in alternating optokinetic nystagmus (OKN) and the perception of binocular motion rivalry. The present study extended these dichoptic motion experiments by introducing obliquely-oriented targets with the aim of probing further the cortical mechanisms underlying binocular processing of motion. Two-dimensional eye movements were recorded along with their subjective perceptual responses. The stimuli consisted of two tilted gratings, one moving diagonally upwards and to the right (UR, 45 degrees ) and the other diagonally upwards and to the left (UL, 135 degrees ), which were presented dichoptically to subjects under two stimulus modes. For the non-exchange mode, the OKN slow phases exhibited three types of directional shifts. Two of these directional shifts tracked the stimuli (i.e. UR or UL), whereas the third moved purely upwards (UP). Since physically there was no upward-moving target, the OKN and perceptual responses appeared to be associated with a perceptual interocular grouping of the two dichoptic stimuli in their reassembled vector-sum direction. The OKN shifts were also found to be highly correlated with the psychophysical responses of motion perception. For the rapid-exchange mode, in which the stimuli were rapidly exchanged between the two eyes, the OKN slow phases exhibited primarily two types of directional shifts, UR and UL, but no UP responses for most subjects. It also appeared that these two coherent motion percepts, UL and UR, were interocularly regrouped from the exchanged stimuli. Moreover, the lack of perceptual grouping to create an UP response in the rapid-exchange mode indicated that temporal integration of at least 200 ms was necessary for the development of a reassembled vector-sum-direction motion percept. The findings under both stimulus modes support the stimulus-feature rivalry hypothesis, in which higher cortical centers mediate interocular perceptual grouping and the associated motor response.
Cerebral Cortex↗
Do component motions recombine into a moving plaid percept?
Two superimposed gratings, which differ in orientation and move independently, combine into a coherently moving plaid if the component gratings are similar. The effect on the plaid motion percept of the addition of texture to each grating was investigated. The texture disambiguates the motion of each component grating. Under the assumption of recombination of first-stage motion detectors into a second stage, which becomes available to perception, one would expect the perceived motion direction of the plaid to change as a result of texture addition. Subjects perceived the oblique motion direction of textured bars of a single orientation correctly. This occurred for texture details with dimensions down to the resolution limit in the fovea (1 min of arc). Two bar patterns with fine texture (1 min of arc details) which differ in orientation were perceived to cohere into a plaid. The plaid's motion direction, however, was independent of the parallel motion components of the bars. For coarser textures (2 and 4 min of arc details) the bar patterns were perceived to slide past one another. In addition, we found that the plaid motion percept occurred less frequently for longer motion sequences, wider bars and for a combination of the component textures at the intersections which is compatible with partial transparency of the bars. These results do not support the two-stage model of Adelson and Movshon (1982), where only the motion component perpendicular to each grating orientation is encoded and where the perception of the plaid motion results from "recombination" of these perpendicular motion components. The data are more in line with a model where first-stage motion detectors are orientation selective but without the restriction that their preferred direction of motion is perpendicular to their preferred orientation. In the second stage it is proposed that combination occurs across the orientation dimension only. This preserves the direction of motion "labels" at the output of the second stage and allows for representation of transparent as well as coherent plaid motion at this stage of processing.
Humans↗
[Model of the perception of perturbed angular motion of the cockpit as part of pilot's information model].
This paper presents the method, algorithm and results of structural identification as a model of pilot's perception of perturbed angular motion of the cockpit and its transmission to the joystick as well as spectral density of the remnant corresponding to the transmission process. Assessments of scalar quasilinear and (more effective) multichannel models of pilot's functions are given. The assessments have been obtained for a single operator. They illustrate the potentials of this procedure.
Algorithms↗
Aging and the perception of biological motion.
Two experiments examined how observers' ability to perceive biological motion changes with increasing age. The observers discriminated among kinetic figures, depicting walking, jogging, and skipping. The direction, duration, and temporal correspondence of the motions were manipulated. Quantitative differences occurred between the recognition performances of younger and older observers, but these differences were often modest. The older and younger observers' performances were comparable for most conditions at stimulus durations of 400 ms. The older observers also performed well above chance at shorter durations of 240 and 120 ms. Unlike their performance on other 2- or 3-dimensional motion tasks, older observers' ability to perceive biological motion is relatively well preserved.
Aged↗
Disruption of eye movements by ethanol intoxication affects perception of depth from motion parallax.
Motion parallax, the ability to recover depth from retinal motion generated by observer translation, is important for visual depth perception. Recent work indicates that the perception of depth from motion parallax relies on the slow eye movement system. It is well known that ethanol intoxication reduces the gain of this system, and this produces the horizontal gaze nystagmus that law enforcement's field sobriety test is intended to reveal. The current study demonstrates that because of its influence on the slow eye movement system, ethanol intoxication impairs the perception of depth from motion parallax. Thresholds in a motion parallax task were significantly increased by acute ethanol intoxication, whereas thresholds for an identical test relying on binocular disparity were unaffected. Perhaps a failure of motion parallax plays a role in alcohol-related driving accidents; because of the effects of alcohol on eye movements, intoxicated drivers may have inaccurate or inadequate information for judging the relative depth of obstacles from motion parallax.
Adult↗
Action categories and the perception of biological motion.
Johansson filmed walkers and runners in a dark room with lights attached to their main joints and demonstrated that such moving light spots were perceived as human movements. To extend this finding the detection and recognition of Johansson displays of different kinds of movements under three light-spot conditions were studied to determine how human actions are perceived on the basis of biological-motion information. Locomotory, instrumental, and social actions were presented in each condition, namely in normal Johansson (light attached to joints), inter-joint (light attached between joints), and upside-down Johansson. Subjects' verbal responses and recognition times were measured. Locomotory actions were recognised better and faster than social and instrumental actions. Furthermore, biological motions were recognised much better and faster when the light-spot displays were presented in the normal orientation rather than upside down. Recognition rate was only slightly impaired under the inter-joint condition. It is argued that the perceptual analysis of actions and movements starts primarily on an intermediate level of action coding and comprises more than just the similarity of movement patterns or simple structures. Additionally, coding of dynamic phase relations and semantic coding take place at very early stages of the processing of biological motion. Implications of these results for computer vision, perceptual models, and mental representations are discussed.
Female↗
Studies on visual perception of locomotion.
The problem about visual discrimination between seeing objects in motion and perception of motion of the perceiver (locomotion) was taken up. A flow of vertical motion was presented to limited areas of the far periphery (45 degrees-90 degrees) of the retina simultaneously with optical information about a stationary room over the rest of the retina. The result was that most subjects perceived themselves as sitting in an elevator continuously moving upward or downward. Thus, peripheral motion stimulation over a few percent of the retinal area determines locomotion perception in apparent competition with information about a static state over the rest of the retina. The same type of stimulus presented to the central part of the retina always brought about perception of object motion and a static perceiver. Effects of size and localization of the area stimulated with the motion flow was studied. Theoretical consequences and problems for further experimental analyses are discussed.
Discrimination, Psychological↗
The perception and discrimination of speed in complex motion.
Random dot kinematograms were used to simulate radial, rotational and spiral optic flow. The stimuli were designed so that, while dot speed increased linearly with distance from the centre of the display, the density of dots remained uniform throughout their presentation. In two experiments, subjects were required to perform a temporal 2AFC speed discrimination task. Experiment 1 measured the perceived speed of a range of optic flow patterns against a rotational comparison stimulus. Radial motions were found to appear faster than rotations by approximately 10%, with a smaller but significant effect for spirals. Experiment 2 measured discrimination thresholds for pairs of similar optic flow stimuli identical in all respects except mean speed. No consistent differences were observed between the speed discrimination thresholds of radial, rotational and spiral motions and a control stimulus with the same speed profile in which motion followed fixed random trajectories. The perceived speed results are interpreted in terms of a model satisfying constraints on motion-in-depth and object rigidity, while speed discrimination appears to be based upon the pooled responses of elementary motion detectors.
Differential Threshold↗
Sources of optical information useful for perception of speed of rectilinear self-motion.
Magnitude judgments of the speed of self-motion were examined. The principal independent variables were edge rate, global optical flow rate, and the type of texture (grid or dot). Results indicated that edge rate and global optical flow rate had additive effects on magnitude judgments, with edge rate accounting for a larger portion of the variance. Effects were independent of texture type. Secondary variables examined were viewing condition and task load. Attempts were made to control the availability of flatness cues. Evidence indicates that the effectiveness of global optical flow rate varied with the control of flatness cues. A secondary running auditory Sternberg task was used to prevent edge counting; the presence of this task did not reduce the effect of edge rate. These results replicate and extend previous work by D. H. Owen and colleagues.
Acceleration↗
Relation between a pilot's sensory perception of linear accelerations and the aircraft motion.
Explore the source record for details and available documents.
Acceleration↗
Patterns of fMRI activity dissociate overlapping functional brain areas that respond to biological motion.
Accurate perception of the actions and intentions of other people is essential for successful interactions in a social environment. Several cortical areas that support this process respond selectively in fMRI to static and dynamic displays of human bodies and faces. Here we apply pattern-analysis techniques to arrive at a new understanding of the neural response to biological motion. Functionally defined body-, face-, and motion-selective visual areas all responded significantly to "point-light" human motion. Strikingly, however, only body selectivity was correlated, on a voxel-by-voxel basis, with biological motion selectivity. We conclude that (1) biological motion, through the process of structure-from-motion, engages areas involved in the analysis of the static human form; (2) body-selective regions in posterior fusiform gyrus and posterior inferior temporal sulcus overlap with, but are distinct from, face- and motion-selective regions; (3) the interpretation of region-of-interest findings may be substantially altered when multiple patterns of selectivity are considered.
Adult↗
An unusual perception accompanying optokinetic nystagmus.
Explore the source record for details and available documents.
Humans↗
The contribution of otoliths and semicircular canals to the perception of two-dimensional passive whole-body motion in humans.
1. Perception of two-dimensional (2-D) whole-body passive motion in the horizontal plane was studied in twelve blindfolded healthy volunteers: pure rotation in place (180 deg), linear motion (4.5 m) and a semicircular trajectory (radius, 1.5 m; angular acceleration, 0.2 rad s-2) were applied in random sequence by means of a remote-controlled robot equipped with a racing-car seat. The seat orientation in the horizontal plane was controlled by the experimenter, independent of the robot trajectory. Thus different degrees of otolith-canal interaction were obtained. The maximal linear acceleration during the semicircular trajectory was 0.1 g; however, the linear acceleration vector was complex as it rotated relative to the subject's head. 2. In the first of two sessions, subjects were instructed to maintain an angular pointer oriented towards a remote (15 m) previously seen target during the passive movements. In the second session they had to make a drawing of the path of the perceived trajectory, after the movement was finished. 3. The results showed that, on average, the movement of the pointer matched the dynamics of the rotatory component of the 2-D motion well. This suggests that, in the range of linear accelerations used in this study, no appreciable influence of otolith input on canal-mediated perception of angular motion occurred. 4. The curvature of the drawn paths was mostly explained by the input to the semicircular canals. Subjects' reconstruction of motion did not account for the directional dynamics of the input to the otoliths occurring during passive motion. 5. This finding proves that reconstructing trajectory in space does not imply a mathematically perfect transformation of the linear and angular motion-related inputs into a Cartesian or polar 2-D representation. Physiological constraints on the interaction between motion direction and change of heading play an important role in motion perception.
Acceleration↗