scholarly journals Apparent Motion and the Pulfrich Effect

Perception ◽  
1975 ◽  
Vol 4 (1) ◽  
pp. 3-18 ◽  
Author(s):  
Michael J Morgan ◽  
Peter Thompson
Keyword(s):  
Apparent Motion ◽  
Target Position ◽  
Moving Object ◽  
Continuous Motion ◽  
Depth Effect ◽  
Pairing Effect ◽  
Moving Stimuli ◽  
Pulfrich Effect

The Pulfrich pendulum effect, obtained by viewing a moving object with a filter over one eye, was examined with target stimuli in apparent, rather than continuous, motion. The filter-induced depth effect persisted until a certain degree of intermittency in the presentations of the target was reached, and then it broke down. The degree of intermittency that could be tolerated before the depth effect broke down increased with the density of the filter. It could be argued that the filter determined a shift in the pairing of successive inputs to the eyes, such that the target position in the unfiltered eye was fused with the preceding target position in the filtered eye. However, it appears that the shifted-pairing effect cannot account for the depth impression seen when the target intermittency is less than about 30 ms. Below this value of intermittency a filter can produce a depth effect even when the delay it introduces is small in comparison to the intermittency of the input. The depth effect seen with intermittencies less than 30 ms appears to be of the same magnitude as that obtained with stimuli in continuous motion. It is concluded that a filter can cause two different kinds of depth shift with apparently moving stimuli.

Response to Motion in Extrastriate Area MSTl: Disparity Sensitivity

1999 ◽  
Vol 82 (5) ◽  
pp. 2462-2475 ◽  
Author(s):  
Satoshi Eifuku ◽  
Robert H. Wurtz
Keyword(s):  
Receptive Field ◽  
Tuning Curve ◽  
Receptive Fields ◽  
Relative Difference ◽  
Moving Object ◽  
Absolute Difference ◽  
Stimulus Motion ◽  
Temporal Area ◽  
Moving Stimuli ◽  
Medial Superior Temporal

Many neurons in the lateral-ventral region of the medial superior temporal area (MSTl) have a clear center surround separation in their receptive fields. Either moving or stationary stimuli in the surround modulates the response to moving stimuli in the center, and this modulation could facilitate the perceptual segmentation of a moving object from its background. Another mechanism that could facilitate such segmentation would be sensitivity to binocular disparity in the center and surround regions of the receptive fields of these neurons. We therefore investigated the sensitivity of these MSTl neurons to disparity ranging from three degrees crossed disparity (near) to three degrees uncrossed disparity (far) applied to both the center and the surround regions. Many neurons showed clear disparity sensitivity to stimulus motion in the center of the receptive field. About [Formula: see text] of 104 neurons had a clear peak in their response, whereas another [Formula: see text] had broader tuning. Monocular stimulation abolished the tuning. The prevalence of cells broadly tuned to near and far disparity and the reversal of preferred directions at different disparities observed in MSTd were not found in MSTl. A stationary surround at zero disparity simply modulated up or down the response to moving stimuli at different disparities in the receptive field (RF) center but did not alter the disparity tuning curve. When the RF center motion was held at zero disparity and the disparity of the stationary surround was varied, some surround disparities produced greater modulation of MSTl neuron response than did others. Some neurons with different disparity preferences in center and surround responded best to the relative disparity differences between center and surround, whereas others were related to the absolute difference between center and surround. The combination of modulatory surrounds and the sensitivity to relative difference between center and surround disparity make these MSTl neurons particularly well suited for the segmentation of a moving object from the background.

scholarly journals Faster processing of moving compared to flashed bars in awake macaque V1 provides a neural correlate of the flash lag illusion

2015 ◽  
Author(s):  
Manivannan Subramaniyan ◽  
Alexander S. Ecker ◽  
Saumil S. Patel ◽  
R. James Cotton ◽  
Matthias Bethge ◽  
...  
Keyword(s):  
Moving Object ◽  
Motion Processing ◽  
Neural Correlate ◽  
Compensatory Mechanisms ◽  
Motion Direction ◽  
Object A ◽  
Moving Stimuli ◽  
Natural Motion ◽  
Statistical Regularities ◽  
The Brain

AbstractWhen the brain has determined the position of a moving object, due to anatomical and processing delays, the object will have already moved to a new location. Given the statistical regularities present in natural motion, the brain may have acquired compensatory mechanisms to minimize the mismatch between the perceived and the real position of a moving object. A well-known visual illusion — the flash lag effect — points towards such a possibility. Although many psychophysical models have been suggested to explain this illusion, their predictions have not been tested at the neural level, particularly in a species of animal known to perceive the illusion. Towards this, we recorded neural responses to flashed and moving bars from primary visual cortex (V1) of awake, fixating macaque monkeys. We found that the response latency to moving bars of varying speed, motion direction and luminance was shorter than that to flashes, in a manner that is consistent with psychophysical results. At the level of V1, our results support the differential latency model positing that flashed and moving bars have different latencies. As we found a neural correlate of the illusion in passively fixating monkeys, our results also suggest that judging the instantaneous position of the moving bar at the time of flash — as required by the postdiction/motion-biasing model — may not be necessary for observing a neural correlate of the illusion. Our results also suggest that the brain may have evolved mechanisms to process moving stimuli faster and closer to real time compared with briefly appearing stationary stimuli.New and NoteworthyWe report several observations in awake macaque V1 that provide support for the differential latency model of the flash lag illusion. We find that the equal latency of flash and moving stimuli as assumed by motion integration/postdiction models does not hold in V1. We show that in macaque V1, motion processing latency depends on stimulus luminance, speed and motion direction in a manner consistent with several psychophysical properties of the flash lag illusion.

Interocular Delay Produces Depth in Subjectively Moving Noise Patterns

1980 ◽  
Vol 32 (3) ◽  
pp. 387-395 ◽  
Author(s):  
M. J. Morgan ◽  
Roger Ward
Keyword(s):  
Apparent Motion ◽  
Visual Noise ◽  
Moving Target ◽  
Dynamic Visual Noise ◽  
Spatial Disparity ◽  
Depth Effect ◽  
Retinal Disparity ◽  
As If

Brief apparent motion sequences were introduced into a dynamic visual dot display by spatially shifting selected dots between successive frames. This causes the display to look as if it is drifting continuously in one direction. When such a display is observed with an interocular delay the drifting dots appear to be displaced in depth, even though there is no conventional retinal disparity in the display. We found that the magnitude of this depth shift increased with the duration of the apparent motion sequences. With sequences of five or more frames duration the depth effect was very similar to that which would have been predicted with a continuously moving target. With briefer sequences the size of the depth effect decreased rapidly. We suggest that apparent motion cascades form the basis of Tyler's dynamic visual noise stereophenomenon, and we question his “random spatial disparity” hypothesis.

Pulfrich Effect and the Filling in of Apparent Motion

Perception ◽  
1976 ◽  
Vol 5 (2) ◽  
pp. 187-195 ◽  
Author(s):  
Michael J Morgan
Keyword(s):  
Eye Movements ◽  
Apparent Motion ◽  
Visual Direction ◽  
Moving Target ◽  
Alignment Technique ◽  
Pulfrich Effect ◽  
Series Of Experiments ◽  
Tracking Eye Movements ◽  
As If

In the stroboscopic version of the Pulfrich effect a filter is able to induce depth shifts in a target as if the latter were moving continuously, rather than merely occupying a series of discrete positions. This was examined in a further series of experiments, in which a visual alignment technique was used to measure the perceived visual direction of an apparently moving target in intervals between its presentations. Results showed that the target has approximately the visual direction that it would have if it were moving continuously. This ‘filling in’ of apparent motion was shown to occur before the level of stereopsis. The possible influence of tracking eye movements is discussed.

The Detection of Interocular Phase Differences

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 272-272
Author(s):  
M J Morgan
Keyword(s):  
Temporal Frequency ◽  
Random Noise ◽  
Broad Band ◽  
Vertical Axis ◽  
Phase Lag ◽  
Depth Effect ◽  
Television Receiver ◽  
Frequency Components ◽  
Pulfrich Effect ◽  
Motion Detectors

When dynamic visual noise such as the ‘snow’ on a detuned television receiver is viewed with a temporal delay between the two eyes, the noise appears to rotate in depth around a vertical axis [Ross, 1974 Nature (London)248 363 – 364; Morgan and Tyler, 1995 Proceedings of the Royal Society of London, Series B262 371 – 376]. Random noise evidently contains a wide spread of spatiotemporal Fourier components, including those for horizontal motion, which may cause a Pulfrich effect when there is an interocular delay. To investigate the temporal-frequency components necessary for the effect, a display was designed containing only a single temporal frequency. Spatially broad-band grey-level noise was flickered, such that each pixel of the noise was sinusoidally modulated over time. An interocular delay was introduced as a phase lag of the flicker in one eye. This produced a rotating depth effect. The threshold for detecting the phase shift was about 5° of phase angle, irrespective of temporal frequency, except for frequencies greater than ∼20 Hz, when the depth effect was no longer seen. Tests of several models of the phase-lag detection are described, including the possibility that there are dichoptic motion detectors also tuned to stereodisparity.

Three-Dimensional Structure from Long-Range Apparent Motion

Perception ◽  
1986 ◽  
Vol 15 (5) ◽  
pp. 619-625 ◽  
Author(s):  
Kvetoslav Prazdny
Keyword(s):  
Long Range ◽  
Apparent Motion ◽  
Three Dimensional ◽  
Temporal Correlation ◽  
Dimensional Structure ◽  
Depth Effect ◽  
Three Dimensional Structure ◽  
Two Dimensional Image ◽  
Kinetic Depth ◽  
Motion Discontinuities

Experiments are reported which show that three-dimensional structure can be perceived from two-dimensional image motions carried by objects defined solely by the differences in binocular and/or temporal correlation (ie disparity or motion discontinuities). This demonstrates that the kinetic depth effect is independent of motion detection in the luminance domain and that its relevant input comes from detectors based on some form of identity preservation of objects or features over time, ie the long-range processes of apparent motion.

Analogue models of motion perception

1980 ◽  
Vol 290 (1038) ◽  
pp. 117-135 ◽  
Keyword(s):  
Visual System ◽  
Frequency Domain ◽  
Motion Perception ◽  
Apparent Motion ◽  
Spatial Interpolation ◽  
Spatial Location ◽  
Moving Object ◽  
Low Frequencies ◽  
Analogue Models ◽  
Spatial Locations

An object moving in discrete spatial jumps is difficult to distinguish from a continuously moving object, provided the time between jumps is not too great. The extent of this perceived continuity may be measured by probing the perceived spatial location at times between the target jumps, by either a vernier alignment or a stereoscopic technique. As the time between jumps increases the accuracy of spatial interpolation falls, until finally the object is seen only at its actual spatial locations. These results can be analysed in the frequency domain by treating the signal for apparent motion as the analogue of a periodic waveform containing relatively low frequencies (the continuous motion) and higher frequencies giving rise to the discreteness of the motion. If such an input has the higher frequencies progressively removed by physical filtering, it is perceived as increasingly continuous. The fact that such filtering is not necessary for perceived continuity when the discrete jumps occur at rates greater than about 30 Hz suggests that frequencies greater than that limit are removed by the visual system itself.

scholarly journals On The Possibility of Identification of the Moving Celestial Objects Observed with the Space Astrometric Telescope

1998 ◽  
Vol 11 (1) ◽  
pp. 585-585
Author(s):  
O.P. Bykov
Keyword(s):  
Angular Velocity ◽  
Apparent Motion ◽  
Statistical Treatment ◽  
Moving Object ◽  
Heavenly Body ◽  
Angular Velocities ◽  
Celestial Bodies ◽  
Motion Parameters ◽  
Special Algorithm

In connection with the creation of the scientific grounds of the Russian Project named “Struve” Space Astrometric System, the main principles of classification and identification of any celestial moving object observed with this System were formulated and basic algorithms were elaborated. These algorithms are invariable for a short or long observational arc, for a known or unknown heavenly body and for an artificial or natural celestial object. For classification of observed celestial bodies the angular velocities of motion are used. These values are calculated from the statistical treatment of the 5 nearest spherical celestial body positions with a time intervalbetween them near 7 seconds. For an identification of well known sky objects ordinary procedure may be used by means of traditional ephemeris calculations. For an identification of unknown natural celestial bodies a special algorithm was developed. Ituses a calculated angular velocity of moving object from one scan to another close scan of observations. Then, having several accurate positions of fixed object during 5-10 hours per day, we can determine an initial elliptical object’s orbit by the Apparent Motion Parameters Method created at Pulkovo Observatory. It deals with a position of object, its angular velocity and acceleration, position’s angle and a curvature of trajectory on a short observational arc. These last four quantities are named the Apparent Motion Parameters. In spite of a preliminary character of the AMP-method orbits we can identify an observed object through a large interval of time, for example over 2-4 months after orbit determination. In this problem the observed and calculated angular velocities of the object’s motion are very useful. They are new and important ephemeris parameters at the epoch of Space Telescope astrometric positional observations. Examples of simulations of orbit determinations will be presented.

Spatial Induction of Illusory Motion

Perception ◽  
1982 ◽  
Vol 11 (2) ◽  
pp. 187-199 ◽  
Author(s):  
Walter C Gogel ◽  
Bernard W Griffin
Keyword(s):  
Apparent Motion ◽  
Alternative Interpretation ◽  
Test Point ◽  
Illusory Motion ◽  
Frontoparallel Plane ◽  
Continuous Motion ◽  
Motion In Depth ◽  
Physical Motion ◽  
Induced Motion

Induced motion is not limited to continuous motions presented on a frontoparallel plane. Experiments were conducted to investigate several varieties of induced motion to which theories of induced motion must apply. The observer indicated the perceived path of motion of a vertically moving test point to which induced motion at right angles to the physical motion was added by the motion of two inducing points. In experiment 1 all motions (both apparently and physically) were in a frontoparallel plane. It was found that discrete displacement as well as continuous motion of the test and inducing points produced substantial amounts of induction. In experiment 2 the inducing points were continuously moved in stereoscopic distance rather than remaining in an apparent frontoparallel plane. A large amount of apparent motion in depth was found in the vertically moving test point and was interpreted as an induced motion in depth. In experiment 3 an alternative interpretation of the phenomenon of experiment 2, in terms of an apparent vergence for the two images of the test point, was investigated and found to be unlikely. In experiment 4, with all the points moving continuously in a frontoparallel plane, eye motions as well as induced motions were measured, with the observer fixating either the test point or an inducing point. Substantial amounts of induction were obtained under both conditions of fixation. The consequences of these findings for theories of induced motion are discussed.

Spatiotemporal Filtering and the Interpolation Effect in Apparent Motion

Perception ◽  
1980 ◽  
Vol 9 (2) ◽  
pp. 161-174 ◽  
Author(s):  
Michael J Morgan
Keyword(s):  
Apparent Motion ◽  
Spatial Position ◽  
Moving Target ◽  
Periodic Modulation ◽  
Continuous Motion ◽  
Spatiotemporal Filtering ◽  
Alignment Technique ◽  
As If

A target moving in discrete spatial steps with an appropriate interstep interval (ISI) can appear visually as if it is in continuous motion. The momentary spatial position of such a target is interpolated by the observer between its real physical positions. The extent of this interpolation was measured by a vernier alignment technique, and was found to decrease as the ISI was lengthened. A discretely moving target may be described as a continuously moving target on which is superimposed a periodic modulation of spatial position. It is shown that the traditional ‘staircase’ stimulus for apparent motion can be generalized to include other kinds of periodic modulation. With the use of various analog-filtered and digitally filtered versions of staircase stimuli with different ISIs, it was shown that the phenomenal interpolation of a periodically modulated moving target was affected only when the frequencies of modulation were less than about 25 Hz. The spatial amplitude of the modulation also has some effect.

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