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At least 595 records · Page 33Linked to original sources
PubMed1996

Method for quantitative estimation of position perception using a joystick during linear movement.

We designed a method for quantitatively estimating self-motion perceptions during passive body movement on a sled. The subjects were instructed to tilt a joystick in proportion to perceived displacement from a giving starting position during linear movement with varying displacements of 4 m, 10 m and 16 m induced by constant acceleration of 0.02 g, 0.05 g and 0.08 g along the antero-posterior axis. With this method, we could monitor not only subjective position perceptions but also response latencies for the beginning (RLbgn) and end (RLend) of the linear movement. Perceived body position fitted Stevens' power law, where R=kSn (R is output of the joystick, k is a constant, S is the displacement from the linear movement and n is an exponent). RLbgn decreased as linear acceleration increased. We conclude that this method is useful in analyzing the features and sensitivities of self-motion perceptions during movement.

Acceleration↗
PubMed1994

Broad tuning for spatial frequency of neural mechanisms underlying visual perception of coherent motion.

Neural events underlying perception of coherent motion are generally believed to be hierarchical: information about local motion is registered by spatio-temporal coincidence detectors whose outputs are cooperatively integrated at a subsequent stage. There is disagreement, however, concerning the spatial scale of the neural filters underlying these operations. According to one class of models, motion registration is initially accomplished in parallel at multiple spatial scales, with filters tuned to lower spatial frequencies responsive to larger motion displacements than filters tuned to higher frequencies. According to another scheme, motion analysis involves a single, broadly tuned spatial filter, with optimal displacement dependent on spacing of local elements. Here we use a masking procedure to measure the extent to which dynamic noise depicted at one spatial scale interferes with detection of coherent motion conveyed by image features at another spatial scale. Our results indicate that a single filter, broadly tuned for spatial frequency, is mediating detection of coherent motion. This finding dovetails with known physiological properties of neurons at an intermediate stage of motion processing.

Fourier Analysis↗
PubMed1995

Otolithic thresholds influence the perception of passive linear displacement.

The vestibular sensors are the necessary source of information for estimating self-displacement during passive linear transport. Displacement has to be computed from the otolith signal by means of an integration process (path integration), which provides a measure of linear acceleration. However, the onset of self-motion perception is delayed due to perceptual thresholds. We investigated the effect of these thresholds on the estimation of passive displacement. Subjects seated on a linear acceleration device (ESA-SLED) were displaced to their left or right. Two tasks were performed: (1) subjects pressed a button when they perceived self-motion; (2) subjects pressed a button when they thought they had reached a previously seen visual target located above the sled rail. Displacement estimation (task 2) was found to depend upon the acceleration magnitude and on the individual motion perception threshold measured in task 1. The results can be explained by assuming that self-displacement computation starts at the onset of self-motion perception and is initialised by a value that is independent of the amplitude of acceleration, thereby compensating for the displacement information lost due to the thresholds.

Acceleration↗
PubMed2004

Response time as an index for selective auditory cognitive deficits.

The full or partial recovery of cognitive functions following brain lesions is believed to rely on the recruitment of alternative neural networks. This has been shown anatomically for selective auditory cognitive functions (Adriani et al. 2003b). We investigate here behavioral correlates that may accompany the use of alternative processing networks and in particular the resulting increase in response times. The performance of 5 patients with right or left unilateral hemispheric infarction and 6 normal control subjects in sound identification, asemantic sound recognition, sound localization, and sound motion perception was evaluated by the number of correct replies and response times for correct and wrong replies. Performance and response times were compared across patients and normal control subjects. Two patients with left lesions were deficient in sound identification and sound motion perception and normal in sound localization and asemantic sound recognition; one patient with right lesion was deficient in sound localization and sound motion perception and normal in sound identification and asemantic sound recognition; deficient performance was associated with increased response times. The remaining 2 patients (1 with left, 1 with right lesion) had normal performance in all 4 tasks but had significantly longer response times in some (but not all) tasks. Patients with normal or deficient performance tended more often than normal subjects to give faster correct than wrong replies. We propose that increased response time is an indication of processing within an alternative network.

Auditory Pathways↗
PubMed2001

Postcoincidence trajectory duration affects motion event perception.

In a two-dimensional display, identical visual targets moving toward and across each other with equal, constant speed can be perceived either to reverse their motion directions at the coincidence point (bouncing percept) or to stream through one another (streaming percept). Although there is a strong tendency to perceive the streaming percept, various factors have been reported to induce the bouncing percept, such as a sound or a visual flash at the moment of the visual target coincidence. By changing duration of the postcoincidence trajectory (PCT), we investigated how long it would take for such bounce-inducing factors to be maximally effective after the visual coincidence. With bounce-inducing factors, the percentage of the bouncing percept did not reach its maximal level immediately after the coincidence but increased as a function of PCT duration up to 150-200 msec. The results clearly reject the possibility of the cognitive-bias hypothesis about the bounce-inducing effect and suggest rather that the bounce-inducing factors have to interact with the PCT for some period after the coincidence to be maximally effective.

Adult↗
PubMed1994

Quantitative judgements and matching of subjective speed of apparent laser speckle flow induced by refractive defocus.

The speed of laser speckles induced by refractive defocus was determined by means of the direct method of free magnitude estimation in combination with sensory verbal descriptors. Physical measures of angular velocities were obtained by matching a similar pattern under the viewer's control to the laser speckles for equal subjective velocity. Theoretical speckle speed was calculated from geometrical formulae proposed by Charman [7]. The velocity percept of apparent speckle motion was a monotonic function of the refractive power of the positive lenses added to the observer's eye, although it exhibited a tendency of levelling off at the greatest strength. The magnitude estimates of this motion percept were highly correlated with corresponding subjective judgements of the angular velocity of the real motion of the matched pattern. Theoretical velocity plotted against empirically obtained values of velocity through matching yielded a product moment correlation coefficient of 0.98 and a regression coefficient of 0.94 indicating a high internal and external validity of these measurements as well as the usefulness of speckle speed as a cue for voluntary changes of the crystalline lens of the eye.

Acceleration↗
PubMed1992

Planar motion permits perception of metric structure in stereopsis.

A fundamental problem in the study of spatial perception concerns whether and how vision might acquire information about the metric structure of surfaces in three-dimensional space from motion and from stereopsis. Theoretical analyses have indicated that stereoscopic perceptions of metric relations in depth require additional information about egocentric viewing distance; and recent experiments by James Todd and his colleagues have indicated that vision acquires only affine but not metric structure from motion--that is, spatial relations ambiguous with regard to scale in depth. The purpose of the present study was to determine whether the metric shape of planar stereoscopic forms might be perceived from congruence under planar rotation. In Experiment 1, observers discriminated between similar planar shapes (ellipses) rotating in a plane with varying slant from the frontal-parallel plane. Experimental conditions varied the presence versus absence of binocular disparities, magnification of the disparity scale, and moving versus stationary patterns. Shape discriminations were accurate in all conditions with moving patterns and were near chance in conditions with stationary patterns; neither the presence nor the magnification of binocular disparities had any reliable effect. In Experiment 2, accuracy decreased as the range of rotation decreased from 80 degrees to 10 degrees. In Experiment 3, small deviations from planarity of the motion produced large decrements in accuracy. In contrast with the critical role of motion in shape discrimination, motion hindered discriminations of the binocular disparity scale in Experiment 4. In general, planar motion provides an intrinsic metric scale that is independent of slant in depth and of the scale of binocular disparities. Vision is sensitive to this intrinsic optical metric.

Adult↗
PubMed1991

Comments on Cavanagh and Mather (1989): coming up short (and long)

Cavanagh and Mather (1989) reviewed literature concerning the possible distinction between short- and long-range processes in motion perception and concluded that the distinction cannot be supported. Instead, they proposed that motion perception be considered on the basis of detectors for first-order (luminance, color) and second-order (first-order motion, texture, stereo) stimulus attributes. They supported their position with studies of motion based on second-order stimuli. The present paper contends that when experiments permitting the investigation of both processes in the same display are included and when criteria are examined in their totality rather than one-by-one, the original short-range/long-range distinction can be retained. Furthermore, it is argued that the first-order/second-order distinction does not represent a theoretical advancement and that studies of second-order motion can be interpreted in terms of the older distinction. It is concluded that the short-range/long-range distinction is useful and should not be abandoned.

Adaptation, Ocular↗
PubMed1999

Motion opponency in visual cortex.

Perceptual studies suggest that visual motion perception is mediated by opponent mechanisms that correspond to mutually suppressive populations of neurons sensitive to motions in opposite directions. We tested for a neuronal correlate of motion opponency using functional magnetic resonance imaging (fMRI) to measure brain activity in human visual cortex. There was strong motion opponency in a secondary visual cortical area known as the human MT complex (MT+), but there was little evidence of motion opponency in primary visual cortex. To determine whether the level of opponency in human and monkey are comparable, a variant of these experiments was performed using multiunit electrophysiological recording in areas MT and MST of the macaque monkey brain. Although there was substantial variability in the degree of opponency between recording sites, the monkey and human data were qualitatively similar on average. These results provide further evidence that: (1) direction-selective signals underly human MT+ responses, (2) neuronal signals in human MT+ support visual motion perception, (3) human MT+ is homologous to macaque monkey MT and adjacent motion sensitive brain areas, and (4) that fMRI measurements are correlated with average spiking activity.

Animals↗
PubMed2003

Pursuit of the ineffable: perceptual and motor reversals during the tracking of apparent motion.

Pursuit can be guided by perceived rather than physical motion, but the temporal relationship between motion perception and pursuit is unknown. We used an apparent motion stimulus consisting of a horizontal row of evenly spaced Kanizsa illusory squares (1.44 deg2): the illusory contours appeared at the midpoints of the illusory squares presented in the previous frame, producing bi-directional apparent motion of the illusory contours (21.5 deg/s) that could be reversed at will. We measured eye movements in five subjects asked to (1) track the motion of the illusory squares, and (2) reverse the perceived direction while continuing to track the squares. We measured the timing of the voluntary perceptual reversals and compared this to the time course of the reversal in tracking direction. We found that subjects could smoothly track the apparent motion of illusory squares and also produce saccade-free reversals in pursuit velocity. The time course of these motor reversals closely followed the measurements of the perceptual reversal and, on average, the perceptual reversals preceded the pursuit reversals by 53 ms, a delay shorter than when the perceptual reversal was visually guided. Smooth pursuit and the perception of motion direction were in temporal register and highly correlated, suggesting that pursuit can provide a real-time readout for the state of motion perception.

Adult↗
PubMed2001

Electroencephalographic activity during perception of motion in childhood.

The purpose of the present study was to relate observations of biological motion to cortical activity by evaluation of the association of quantified electroencephalogram (qEEG) parameters with a video film projection. Thirty right-handed healthy children (2-8-year-olds) viewed a video film showing still shots and moving shots with human movement or object movement. The EEG was recorded while children watched the video movie and was then subjected to spectral analysis; the spectral powers for theta, alpha and beta bands were matched with corresponding sequences of video film. The power values of each frequency band were analysed in a four-way repeated-measures ANOVA (Age x Hemisphere x Electrode x Sequence). Three main results were obtained: (i) younger children (2-4-year-olds) had higher power spectral values than older children (5-8-year-olds); (ii) greater EEG desynchronization of the left hemisphere was observed; (iii) observation of biological movement was related to a significant decrease in theta 1 and theta 2 power values of EEG in fronto-temporal and central regions of the left hemisphere compared with visual perception of still shots or nonhuman movement. These results indicated some support for the theory that the sensori-motor cortex and Broca's area are activated during visual observation of human motion.

Age Factors↗
PubMed2006

Adaptation aftereffects in the perception of gender from biological motion.

Human visual perception is highly adaptive. While this has been known and studied for a long time in domains such as color vision, motion perception, or the processing of spatial frequency, a number of more recent studies have shown that adaptation and adaptation aftereffects also occur in high-level visual domains like shape perception and face recognition. Here, we present data that demonstrate a pronounced aftereffect in response to adaptation to the perceived gender of biological motion point-light walkers. A walker that is perceived to be ambiguous in gender under neutral adaptation appears to be male after adaptation with an exaggerated female walker and female after adaptation with an exaggerated male walker. We discuss this adaptation aftereffect as a tool to characterize and probe the mechanisms underlying biological motion perception.

Adaptation, Physiological↗
PubMed2005

A common mechanism for the perception of first-order and second-order apparent motion.

A common mechanism for perceiving first-order, luminance-defined, and second-order, texture-contrast defined apparent motion between two element locations is indicated by: (1) transitivity--whether or not motion is perceived is inter-changeably affected by activationally equivalent luminance and contrast changes at each location, (2) local integration--whether or not motion is perceived depends on the net activation change resulting from simultaneous background-relative luminance and background-relative contrast changes at the same element location, and (3) inseparability--apparent motion is not perceived through independent first- or second-order mechanisms when luminance and contrast co-vary at the same location. These results, which are predicted by the response characteristics of directionally selective cells in areas V1, MT, and MST, are not instead attributable to changes in the location of the most salient element (third-order motion), attentive feature tracking, or artifactual first-order motion. Their inconsistency with Lu and Sperling's [Lu, Z., Sperling, G. (1995a). Attention-generated apparent motion. Nature 377, 237, Lu, Z., Sperling, G. (2001). Three-systems theory of human visual motion perception: review and update. Journal of the Optical Society of America A 18, 2331] model, which specifies independent first- and second-order mechanisms, may be due to computational requirements particular to the motion of discrete objects with distinct boundaries defined by spatial differences in luminance, texture contrast, or both.

Contrast Sensitivity↗
PubMed1997

Forward-facing motion biases for rigid and nonrigid biologically likely transformations.

When observers are presented directionally ambiguous motion, they exhibit a bias for experiencing movement in the direction in which shapes appear to face. We examined the influence of rigidity of a shape on the forward-facing bias with stimuli whose directionality is biologically specified. In general, the lack of shape correspondence during a nonrigid transformation should weaken the motion percept and decrease forward-facing bias. In contrast, representational momentum cues associated with a biologically likely nonrigid transformation should enhance the motion percept and increase forward-facing bias. Analysis for both rigid and nonrigid conditions indicated statistically significant forward-facing biases, but strength of bias did not differ significantly. The lack of difference between the two conditions suggests that the transformation was not one which allowed the influence of either consistency of correspondence or representational momentum to dominate and confirms that a comparably sized forward-facing bias can occur with both rigidly and nonrigidly transformed shapes.

Cues↗
PubMed1998

Transient change in standing posture after linear treadmill locomotion.

Postural sway was measured in 24 healthy subjects after running or walking with eyes open on a standard treadmill exerciser. The speeds of running and walking were set at 10 and 7 km/h, respectively, and locomotion was maintained for 7 min. The postural sway response was characterized by systematic forward displacement followed by gradual decay to baseline and was accompanied by self-motion perception. Mean fore-back postural after sway was significantly greater after treadmill running than after normal running. The aftereffects of treadmill walking were significantly less than those of treadmill running. The 6 subjects showing distinct forward postural sway after treadmill walking were instructed to walk on the treadmill with their eyes closed. After this, none of the 6 subjects felt self-motion perception and had no evidence of postural aftersway. These results clearly demonstrate that vision during treadmill locomotion plays an important role in evoking postural sway after treadmill locomotion. It can be inferred that somatosensory/motor signals may be stored during visual-somatosensory/motor conflict and that this stored information may evoke postural change and self-motion perception.

Adult↗
PubMed2005

Paucity of chromatic linear motion detectors in macaque V1.

The motion of a color-defined edge is often more difficult to perceive than the motion of a luminance-defined edge. Neurons subserving motion vision may therefore be particularly sensitive to luminance contrast. One class of neurons thought to play a critical role in motion perception is V1 neurons whose spatiotemporal receptive fields are oriented in space-time. We used the reverse correlation technique to study the relationship between color tuning and space-time receptive field orientation in V1 neurons of awake, fixating monkeys. Neurons with space-time oriented receptive fields were tuned almost exclusively for luminance, whereas neurons with nonoriented space-time receptive fields were tuned for luminance or for color. These results suggest that the special role of luminance contrast in motion perception is due in part to the establishment of space-time oriented receptive fields among luminance-tuned, but not color-tuned, V1 neurons.

Animals↗
PubMed2006

Bayesian processing of vestibular information.

Complex self-motion stimulations in the dark can be powerfully disorienting and can create illusory motion percepts. In the absence of visual cues, the brain has to use angular and linear acceleration information provided by the vestibular canals and the otoliths, respectively. However, these sensors are inaccurate and ambiguous. We propose that the brain processes these signals in a statistically optimal fashion, reproducing the rules of Bayesian inference. We also suggest that this processing is related to the statistics of natural head movements. This would create a perceptual bias in favour of low velocity and acceleration. We have constructed a Bayesian model of self-motion perception based on these assumptions. Using this model, we have simulated perceptual responses to centrifugation and off-vertical axis rotation and obtained close agreement with experimental findings. This demonstrates how Bayesian inference allows to make a quantitative link between sensor noise and ambiguities, statistics of head movement, and the perception of self-motion.

Acceleration↗