The formation of stripe patterns in animal skin has been explained by the reaction-diffusion (RD) system, a hypothetical chemical reaction proposed by A. Turing. Although animal stripes usually have directionality, the RD model alone cannot explain how the direction is specified. To investigate the mechanism regulating the direction of stripes, ...

Human exhibits an anisotropy in direction perception: discrimination is superior when motion is around horizontal or vertical rather than diagonal axes. In contrast to the consistent directional anisotropy in perception, we found only small idiosyncratic anisotropies in smooth pursuit eye movements, a motor action requiring accurate discrimination of visual motion ...

Motion is one of the most efficient cues for shape perception. We conducted behavioral experiments to examine how monkeys perceive shapes defined by motion cues and whether they perceive them as humans do. We trained monkeys to perform a shape discrimination task in which shapes were defined by the motion ...

The Pulfrich effect yields a perceived depth for horizontally moving objects but not for vertically moving ones. In this study the Pulfrich effect was measured by translating oblique lines seen through a circular window, which made motion direction ambiguous. Overlaying random dots that moved horizontally, vertically, or diagonally controlled the ...

Attentional effects on self-motion perception (vection) were examined by using a large display in which vertical stripes containing upward or downward moving dots were interleaved to balance the total motion energy for the two directions. The dots moving in the same direction had the same colour, and subjects were asked ...

This paper follows from studies by Joung, van der Zwan and Latimer (2000) in which symmetrical dot patterns with one axis of symmetry were used to produce tilt aftereffects (TAEs). The present paper investigates TAE functions produced by symmetrical dot patterns with multiple axes of symmetry. In Experiments 1 and ...

Previous research has shown that a field of random dots in which each dot alternates between a slow and a fast speed, can give rise to the percept of two superimposed sheets of moving dots when the alternations are out of phase or asynchronous with each other [Vis. Res. 35 ...

The metatherians (marsupials) have been separated from eutherians (placentals) for approximately 135 million years. It might, therefore, be expected that significant independent evolution of the visual system has occurred. The present paper describes for the first time the orientation, direction and spatiotemporal tuning of neurons in the primary visual cortex ...

A primary task of the visual system is to extract the direction and speed of animate objects from the retinal image. We examined global speed processing by determining how local speeds are integrated and whether integration occurs across all speeds or within fixed speed ranges. The first experiment addressed how ...

Microstimulation of direction columns in the middle temporal visual area (MT, or V5) provides a powerful tool for probing the relationship between cortical physiology and visual motion perception. In the current study we obtained "veridical" reports of perceived motion from rhesus monkeys by permitting a continuous range of possible responses ...

The purpose of this work was to evaluate the effects of central and peripheral stimulation on the perception of optic flow over large spatial extents. Coherence thresholds were measured for RDKs simulating observer translation and radial motion. Experiments 1 and 3a measured sensitivity to a range of speeds for a ...

Direction selectivity (DS) of simple cells in the primary visual cortex was recently suggested to arise from short-term synaptic depression in thalamocortical afferents (Chance F, Nelson S, Abbott L (1998), J. Neuroscience 18(12): 4785-4799). In the model, two groups of afferents with spatially displaced receptive fields project through either depressing ...

Determining the direction of visual motion poses a serious problem for any visual system, given the inherent ambiguities. Geisler (1999) has suggested that motion streaks left in the wake of a moving target provide a rich source of potential information that could aid in resolving direction ambiguities. Here we provide ...

This paper summarizes recent work showing that tactile roughness appreciation increases in a nearly linear fashion as tactile element spacing or spatial period (SP, distance centre-to-centre between raised dots in these experiments) is increased from 1.5 to 8.5 mm. Although a previous study had reported a U-shaped psychophysical function peaking ...

Glass patterns are texture stimuli made by pairing randomly placed dots with partners at specific offsets. The strong percept of global form that arises from the sparse local orientation cues has made these patterns the subject of psychophysical investigations, yet neuronal responses to Glass patterns have not been studied. We ...

We studied the spatial organization of direction of motion in visual area MT of the Cebus apella monkey. We used arrays of 6 (700 micro m apart) parallel electrodes in penetrations tangential to the cortical layers to record multi-unit responses to moving bars, at 200 micro m steps. We determined ...

We investigated global motion detection in binocularly deprived cats (BD cats) and control cats (C cats). The cats were trained in the two-choice free running apparatus for a food reward. The positive stimulus was a moving random-dot pattern with all dots moving in one direction, the negative stimulus was the ...

Twelve pigeons ( Columba livia) were trained on a go/no-go schedule to discriminate between two kinds of movement patterns of dots, which to human observers appear to be "intentional" and "non-intentional" movements. In experiment 1, the intentional motion stimulus contained one dot (a "wolf") that moved systematically towards another dot ...

If a dot is flashed in perfect alignment with a pair of dots rotating around the visual fixation point, most observers perceive the rotating dots as being ahead of the flashing dot (flash-lag effect). This perceptual effect has been interpreted to result from the perceptual extrapolation of the moving dots, ...

We recorded from ON-OFF direction-selective ganglion cells (DS cells) in the rabbit retina to investigate in detail the inhibition that contributes to direction selectivity in these cells. Using paired stimuli moving sequentially across the cells' receptive fields in the preferred direction, we directly confirmed the prediction of that a wave ...

Using the scleral search coil technique to monitor eye movements, we recorded short-latency ocular following responses to displacement steps of large random-dot patterns. On half of the trials, the luminance of the dots and background were reversed during the step, a procedure that is known to reverse the direction of ...

As an electrical analog of the optical Hanbury Brown-Twiss effect, we study current cross correlations in a chaotic quantum dot-superconductor junction. One superconducting and two normal reservoirs are connected via point contacts to a chaotic quantum dot. For a wide range of contact widths and transparencies, we find large positive ...

Previous studies of spatial transformations between sensory input and motor output in escape responses have suggested two alternative patterns of spatial integration. The continuous pattern corresponds to withdrawal movements directed 180 degrees away from the location of the stimulus, whereas the categorical pattern corresponds to movements that are biased toward ...

When observers are asked to judge the first position of a moving object, displacements of the judged onset in the direction of and in the direction opposite to the motion have been reported. These errors have been referred to as the Fröhlich illusion and the onset repulsion effect, respectively. To ...

Participants estimated the perceptual center of mass between two horizontally oriented black dots varying in size and distance. Experiment 1 showed that estimates, measured as distance from the larger dot's center, decreased with an increase in size ratio between the dots and a decrease in the distance between them, as ...

Experiments examined differential coding of acoustic particle motion axis in the auditory midbrain of goldfish. Animals were exposed to vibratory stimuli varying in axis orientation as action potentials were recorded from single units in the central neuropil of nucleus centralis in the torus semicircularis. Response magnitudes as a function of ...

Previously, Y. Jiang, P. Greenwood, and R. Parasuraman (1999) reported that priming of rotating three-dimensional visual objects is age sensitive. The current study investigated whether there is also an age-related difference in priming with simple two-dimensional (2-D) moving stimuli (i.e., whether a prime stimulus moving in a particular direction causes ...

We measured the effects of coherent motion of one set of dots on the perceived location of Gaussian envelopes formed by luminance modulation of a second set of dots. Perceived shifts in envelope location in the direction of coherent motion were obtained even when the dots forming the envelopes did ...

The effect of stimulus motion on retrospective time judgments was investigated in four experiments. Subjects reproduced the duration of a 32-s interval which was filled by either a stationary or moving visual element presented on a computer monitor. In Experiments 1 and 4, the element moved horizontally back and forth, ...

If a pair of dots, diametrically opposed to each other, is flashed in perfect alignment with another pair of dots rotating about the visual fixation point, most observers perceive the rotating dots as being ahead of the flashing dots (flash-lag effect). This psychophysical effect was first interpreted as the result ...

Five subjects observed a random dot pattern that moved horizontally within a rectangular, 40 deg x 4 deg invisible aperture. The long side of this aperture was either parallel or perpendicular to the direction of motion. A two-interval forced-choice procedure was employed for measuring the thresholds for detection of 100-ms ...

We present an experimental study of the directional-solidification patterns of a nematic-smectic-B front. The chosen system is C4H9-(C6H10)2CN (in short, CCH4) in 12 microm-thick samples, and in the planar configuration (director parallel to the plane of the sample). The nematic-smectic-B interface presents a facet in one direction-the direction parallel to ...

To reduce the information gap between human neuroimaging and macaque physiology and anatomy, we mapped fMRI signals produced by moving and stationary stimuli (random dots or lines) in fixating monkeys. Functional sensitivity was increased by a factor of approximately 5 relative to the BOLD technique by injecting a contrast agent ...

Whereas it is a well known fact that objects appear to move faster in smaller stimulus fields, the reason for such a misjudgement of speed is still a matter of debate. We present four experiments to characterise the stimulus parameters that are important for the apparent speed increase of dots ...

The effect of sensory input on hormones is essential to any explanation of mammalian behavior, including aspects of physical attraction. The chemical signals we send have direct and developmental effects on hormone levels in other people. Since we don t know either if, or how, visual cues might have direct ...

This study was conducted to determine whether humans' judgments about the speed and direction of moving stimuli was differentially affected by transcranial magnetic stimulation (TMS). Subjects viewed two successively presented moving stimuli that differed from each other both in speed and direction of motion. Single-pulse TMS was applied either medially ...

PURPOSE: To measure psychophysically the thresholds for motion detection in the nasal and temporal directions under monocular viewing conditions in monkeys reared under conditions of daily alternating monocular occlusion (AMO). The hypothesis was that motion perception would be asymmetric with more sensitivity for motion in the nasal direction. METHODS: Three ...

For the accurate perception of multiple, potentially overlapping, surfaces or objects, the visual system must distinguish different local motion vectors and selectively integrate similar motion vectors over space to segment the retinal image properly. We recently showed that large differences in speed are required to yield a percept of motion ...

An apparent motion stimulus is used to probe the interactions between signals representing brightness increments (ON stimuli) and decrements (OFF stimuli) in the directional motion detectors forming the input to the nucleus of the optic tract (NOT) of the wallaby, Macropus eugenii. Direction-selective NOT neurons increase their firing rates during ...

Motion onset evoked visual potentials are dominated by a negativity (N2) at occipital electrodes and a positivity (P2) at the vertex. The degree of true motion processing reflected by N2 and P2 was estimated from the direction specificity of motion adaptation. Adapting stimuli moved to the right and test stimuli ...

Several types of electrical events occur in the small intestine but their spatial and temporal contributions to overall motility are not clear. In order to quantify local motility in greater detail, a new technique of recording and analysing movements at multiple sites was developed. Use was made of isolated segments ...

Local motion detectors can only provide the velocity component perpendicular to a moving line that crosses their receptive field, leading to an ambiguity known as the "aperture problem". This problem is solved exactly for rigid objects translating in the screen plane via the intersection of constraints (IOC). In natural scenes, ...

Direction-specific losses in sensitivity were found for a test grating which was superimposed on a stationary contrast pedestal and which moved either in the same or opposite direction as a prior biasing stimulus. Three types of biasing stimuli were employed: a grating swept through 270 degrees in 45 degrees steps, ...

Two populations of limbic neurons are likely neurophysiological substrates for cognitive operations required for spatial orientation and navigation: hippocampal pyramidal cells discharge selectively when the animal is in a certain place (the "firing field") in the environment, whereas head direction cells discharge when the animal orients its head in a ...

Growing evidence from psychophysics and single-unit recordings suggests specialised mechanisms in the primate visual system for the detection of complex motion patterns such as expansion and rotation. Here we used a subthreshold summation technique to determine the direction tuning functions of the detecting mechanisms. We measured thresholds for discriminating noise ...

PURPOSE: Psychophysical studies indicate that many dyslexics have a motion-processing deficit. The purpose of this study was to determine whether elevated motion coherence thresholds correlate with the specific dyslexic subtypes as defined by the Boder classification scheme. METHODS: Twenty-one dyslexics (seven dyseidetics, six dysphonetics, and eight dysphoneidetics) and 19 age- ...

Knowing the direction and speed of moving objects is often critical for survival. However, it is poorly understood how cortical neurons process the speed of image movement. Here we tested MT neurons using moving sine-wave gratings of different spatial and temporal frequencies, and mapped out the neurons' spatiotemporal frequency response ...

PURPOSE: The purpose of this experiment was to study visuomotor localization in the presence of either a horizontal array of equally spaced dots or a thin horizontal line. METHODS: Pointing behavior was used to assess directional localization. In experiment 1, subjects were made myopic using a contact lens and then ...

Affine geometry is a generalization of Euclidean geometry in which distance can be scaled along parallel directions, though relative distances in different directions may be incommensurable. This article presents a new procedure for testing the intrinsic affine structure of a psychological space by having subjects perform bisection judgments over multiple ...

Farmed silver foxes (Vulpes vulpes) were allowed to balance their known preference for an elevated floor against their presumed preference for a sand floor. In Experiment 1, foxes had to choose between two identical cages, connected with an opening. One cage had a wire floor and the other had a ...