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PubMedDate not supplied

On-chip visual perception of motion: a bio-inspired connectionist model on FPGA.

Visual motion provides useful information to understand the dynamics of a scene to allow intelligent systems interact with their environment. Motion computation is usually restricted by real time requirements that need the design and implementation of specific hardware architectures. In this paper, the design of hardware architecture for a bio-inspired neural model for motion estimation is presented. The motion estimation is based on a strongly localized bio-inspired connectionist model with a particular adaptation of spatio-temporal Gabor-like filtering. The architecture is constituted by three main modules that perform spatial, temporal, and excitatory-inhibitory connectionist processing. The biomimetic architecture is modeled, simulated and validated in VHDL. The synthesis results on a Field Programmable Gate Array (FPGA) device show the potential achievement of real-time performance at an affordable silicon area.

Models, Neurological↗
PubMed1999

Vestibular and vestibulo-proprioceptive perception of motion in the horizontal plane in blindfolded man--III. Route inference.

The inference of direction and length of a subsequent route during performance of a triangle completion task was studied in blindfolded human subjects. Subjects were transported and walked with guidance along two sides of left- and right-oriented isosceles triangles. Subjects had to walk without assistance along the inferential bases of triangles back to a starting point. The influence of two variables in the triangular trajectory--the side length (2, 3 and 4 m) and the angle between sides (30-150 degrees--on route inference accuracy was investigated. Changes in the length of the movement trajectory with retained configuration lead to an alteration in the linear but not the angular estimation of the inferred route. Changes in the configuration of equidistant movement trajectories result in an alteration in both the linear and angular estimations of the inferred route. Estimations of direction and length of inferred routes following passive transportation and those following walking along triangular sides showed similar degrees of accuracy. When the inference of a route was regarded as a geometrical sum of subjective angular and linear estimations of displacements, trajectories of backward paths could be predicted. The results obtained show that the vestibular cue can only provide a gross orientation when moving along a complex trajectory in the horizontal plane; the proprioceptive cue does not improve accuracy adequately.

Adult↗
PubMed1994

Segregation of computations underlying perception of motion discontinuity and coherence.

Motion is one of the most important cues for detecting discontinuities in images. The major dichotomy among theories of motion-defined discontinuity concerns whether the computations related to the extraction of discontinuity and large scale integration of motion signals are organized hierarchically or occur simultaneously in the brain. In this study we investigated the hierarchical nature of these computations using data from two patients with unilateral brain lesions on two psychophysical tasks: one requiring motion for spatial integration of direction in a stochastic motion field, and the other requiring motion to extract discontinuities in the same type of stimuli. The results showed a surprising double dissociation of deficits on these motion tasks which suggests that models for discontinuity detection requiring a single neural substrate for computing coherence and discontinuity are unlikely to be applicable to the human visual system. We discuss the computational implications of these results. Using morphometric three-dimensional reconstructions of the lesions from the magnetic resonance imaging data we suggest possible anatomical sites mediating these computations.

Adult↗
PubMed1985

Spatiotemporal energy models for the perception of motion.

A motion sequence may be represented as a single pattern in x-y-t space; a velocity of motion corresponds to a three-dimensional orientation in this space. Motion sinformation can be extracted by a system that responds to the oriented spatiotemporal energy. We discuss a class of models for human motion mechanisms in which the first stage consists of linear filters that are oriented in space-time and tuned in spatial frequency. The outputs of quadrature pairs of such filters are squared and summed to give a measure of motion energy. These responses are then fed into an opponent stage. Energy models can be built from elements that are consistent with known physiology and psychophysics, and they permit a qualitative understanding of a variety of motion phenomena.

Humans↗
PubMed2002

The far-anchor effect: errors in the perception of motion and implications for aviation safety.

The far-anchor effect is responsible for a motion-in-depth illusion that has only recently been recognized. When viewing conditions are limited, motions in depth of a farther target in a two-object display may readily be perceived as opposite motions in depth of the nearer target. The present studies determined whether this error could be avoided through controlled fixation or training with feedback. Under conditions of reduced visibility, participants (college students) viewed 64 two-target presentations varying in the position of the moving target and its direction of motion. Neither fixation instructions nor informational feedback about motion errors affected the occurrence of the basic illusion, nor did a vertical separation of the targets eliminate the main effect, indicating the robustness of the motion illusion under some relatively realistic variations. Such errors in judging motion in depth have significance for both midair collisions between aircraft and ground-incursion accidents under conditions of reduced visibility. Potential applications include the elaboration of examples used in pilot training programs or in training programs for ground personnel.

Accidents, Aviation↗
PubMed2003

Reversed-phi perception with motion-defined motion stimuli.

Perception of reversed-phi with motion-defined motion (MDM) stimuli was examined while varying various parameters including eccentricity. For peripheral viewing, reversed-phi was observed at all displacements between 30 degrees and 135 degrees. The perception most prominent at 90 degrees, but was disrupted by dichoptic presentation. These results suggest operations of an energy-based motion system similar to the first-order motion system for luminance motion, which most likely resides at a relatively early level (cf. [Vision Res. 33 (1993) 533]). For central viewing, reversed motion was observed only for larger displacements. The perceived motion at smaller displacements was predominantly in the forward direction. Transition between the two modes occurred around 90 degrees displacement. In addition, this motion perception was not disrupted by dichoptic presentation. This indicated the operation of a polarity independent matching-based motion system residing at a higher-level. Thus, the results indicate the involvement of at least two separate mechanisms for MDM detection, and that there is a dominance shift between the two systems according to the eccentricity.

Contrast Sensitivity↗
PubMed1975

Perception of linear horizontal self-motion induced by peripheral vision (linearvection) basic characteristics and visual-vestibular interactions.

The basic characteristics of the sensation of linear horizontal motion have been studied. Objective linear motion was induced by means of a moving cart. Visually induced linear motion perception (linearvection) was obtained by projection of moving images at the periphery of the visual field. Image velocity and luminance thresholds for the appearance of linearvection have been measured and are in the range of those for image motion detection (without sensation of self motion) by the visual system. Latencies of onset are around 1 sec and short term adaptation has been shown. The dynamic range of the visual analyser as judged by frequency analysis is lower than for the vestibular analyser. Conflicting situations in which visual cues contradict vestibular and other proprioceptive cues show, in the case of linearvection a dominance of vision which supports the idea of an essential although not independent role of vision in self motion perception.

Adaptation, Psychological↗
PubMed1998

Opponent motion interactions in the perception of transparent motion.

Interactions in the perception of motion transparency were investigated using a signal-detection paradigm. The stimuli were the linear sum of two independent, moving, random-check "signal" textures and a third texture consisting of dynamic random "noise." Performance was measured as the ratio of squared signal and noise contrasts was varied (S2/N2). Motion detectability was poorest when the two signal textures moved in opposite directions (180 degrees), intermediate when they moved in the same direction (0 degrees), and best when the textures moved in directions separated by 90 degrees in the stimulus plane. This pattern of results held across substantial variations in velocity, field size, duration, and texture-element size. Motion identification was also impaired, relative to 0 degrees, in the 180 degrees but not in the 90 degrees condition. These results are consistent with the idea that performance in the opponent-motion condition is limited by inhibitory (or suppressive) interactions. These interactions, however, appear to be direction specific: little, if any, inhibition was observed for perpendicular motion.

Humans↗
PubMed2002

Deficits of motion transparency perception in adult developmental dyslexics with normal unidirectional motion sensitivity.

We assessed motion integration ability in seven adult developmental dyslexics using unidirectional and bidirectional (transparent) random dot kinematograms (RDKs) that varied in the number of frames. All adult dyslexics performed as well as normally reading age-matched controls with unidirectional RDKs, regardless of frame number. However, using orthogonal motion transparent stimuli, deficits were obvious in six dyslexics and depended on frame number. Whereas controls needed on average only 4.4 frames (144 ms) to identify both directions correctly on 75% of presentations, dyslexics needed on average 14.6 frames (483 ms) to achieve this level of performance. Even though a unidirectional motion task failed to reveal processing abnormalities in adult dyslexics, the motion transparency task was effective at revealing significant perceptual dysfunction, suggesting that performance on this task is a better psychophysical indicator of visual motion deficits in dyslexia. This finding provides little support for the magnocellular deficit hypothesis and, rather, points to abnormality within dorsal extrastriate cortical areas that subserve the integration and segmentation of complex motion signals.

Adult↗
PubMed1993

Optical tearing in spatiotemporal boundary formation: when do local element motions produce boundaries, form, and global motion?

Perception of continuous boundaries, shape, and global motion can be produced by transformations in local elements separated in both space and time, a process here called spatiotemporal boundary formation (SBF). Prior research has shown that a broad class of element transformations gives rise to SBF. The present work used the transformation of local element displacement to explore the initiating conditions for SBF. Three experiments assessed SBF using a 10-alternative, forced-choice, shape identification task. Experiment 1a showed that large element displacements, but not small ones, produced high accuracy in shape identification. Experiment 1b tested the detectability of the small and large element displacements in an unrelated task, indicating that the results of Experiment 1a were not due to poor detectability for small displacements. Experiment 2 found no variation in SBF performance with changes in viewing distance. Experiment 3 provided evidence that initiating SBF depends on a ratio of element displacement to element separation. These results support an interpretation of SBF as a process geared to detection of object boundaries from spatiotemporal change. Initiating SBF requires transformations in local elements that are classified as spatiotemporal discontinuities (STDs). Small element displacements in a display of a given density do not register as STDs because they are classified as local deformations in an intact, implicit surface connecting visible elements. Complementarity is suggested between element changes which preserve continuity with their neighbors (optic flow) and those comprising spatiotemporal discontinuities (optic tearing). Classification of element transformations as optic flow or tearing may determine whether they provide information about surface form (e.g., through structure-from-motion) or about object boundaries, through SBF.

Form Perception↗
PubMed1998

A computational and perceptual account of motion lines.

To indicate motion in a static drawing, artists often include lines trailing a moving object. The use of these motion lines is notable because they do not seem to be related to anything in the optic array. The dynamic behavior of a neural-network model for contour detection is analyzed and it is shown that it generates trails of oriented responses behind moving stimuli. The properties of the oriented response trails are shown to correspond to motion lines. The model generates trails of different orientations depending on the speed and length of the movement, and thereby predicts different uses of two types of motion lines. The model further predicts that motion lines should bias real motion in some situations. An experiment relating motion lines to ambiguous motion percepts demonstrates that motion lines contribute to motion percepts.

Humans↗