Spatial Gating Effects on Judged Motion of Gratings in Apertures

Power, R. P.; Moulden, Bernard

doi:10.1068/p210449

Cited by 21 publications

(17 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Occlusion cues reduce the effect of terminators, as found previously for other depth cues (Shimojo et al, 1989;Stoner et al, 1990;Duncan et al, 2000), and the effect of terminators seems to be quite local in visual space (Power and Moulden, 1992;Kooi, 1993). However, the magnitude of the effects seen for perception is substantially larger than that seen in our population of MT cells.…”

Section: Integration Of Motion Cues In Perception and Behaviorcontrasting

confidence: 51%

See 1 more Smart Citation

Integration of Contour and Terminator Signals in Visual Area MT of Alert Macaque

Pack

Gartland²,

Born³

2004

J. Neurosci.

View full text Add to dashboard Cite

The integration of visual information is a critical task that is performed by neurons in the extrastriate cortex of the primate brain. For motion signals, integration is complicated by the geometry of the visual world, which renders some velocity measurements ambiguous and others incorrect. The ambiguity arises because neurons in the early stages of visual processing have small receptive fields, which can only recover the component of motion perpendicular to the orientation of a contour (the aperture problem). Unambiguous motion signals are located at end points and corners, which are referred to as terminators. However, when an object moves behind an occluding surface, motion measurements made at the terminators formed by the intersection of the object and the occluder are generally not consistent with the direction of object motion. To study how cortical neurons integrate these different motion cues, we used variations on the classic "barber pole" stimulus and measured the responses of neurons in the middle temporal area (MT or V5) of extrastriate cortex of alert macaque monkeys. Our results show that MT neurons are more strongly influenced by the unambiguous motion signals generated by terminators than to the ambiguous signals generated by contours. Furthermore, these neurons respond better to terminators that are intrinsic to a moving object than to those that are accidents of occlusion. V1 neurons show similar response patterns to local cues (contours and terminators), but for large stimuli, they do not reflect the global motion direction computed by MT neurons. These observations are consistent with psychophysical findings that show that our perception of moving objects often depends on the motion of terminators.

show abstract

Section: Integration Of Motion Cues In Perception and Behaviorcontrasting

confidence: 51%

“…8a). In this case, the barber pole illusion is abolished, and observers perceive the grating to be moving perpendicular to its orientation (Power and Moulden, 1992;Kooi, 1993).…”

Section: Effect Of Aperture Shapementioning

confidence: 98%

Integration of Contour and Terminator Signals in Visual Area MT of Alert Macaque

Pack

Gartland²,

Born³

2004

J. Neurosci.

View full text Add to dashboard Cite

show abstract

“…Lorenceau & Shiffrar, 1992;Shiffrar et al, 1995). Psychophysical studies of the "barber pole" illusion indeed suggest that local 1D and 2D motion signals compete to drive the motion direction perception (Power & Moulden, 1992;Kooi, 1993;Castet et al, 1999). In that sense, the "barber pole" illusion is a powerful tool to investigate surface motion processing.…”

Section: Early and Late Components Of Tracking Initiationmentioning

confidence: 99%

“…Shimojo et al, 1989;Shiffrar et al, 1995;Castet et al, 1999). In understanding how grating and terminator motion signals are integrated, one important step is to tease apart the respective roles of low-level mechanisms, such as spatial interactions between different local motion signals (Power & Moulden, 1992) and higher-level mechanisms, such as occlusion rules or depth perception (Nakayama & Silverman, 1988;Shimojo et al, 1989;Anderson & Sinhia, 1997;Castet et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Temporal dynamics of motion integration for the initiation of tracking eye movements at ultra-short latencies

et al. 2000

View full text Add to dashboard Cite

The perceived direction of a grating moving behind an elongated aperture is biased towards the aperture's long axis. This "barber pole" illusion is a consequence of integrating one-dimensional (1D) or grating and two-dimensional (2D) or terminator motion signals. In humans, we recorded the ocular following responses to this stimulus. Tracking was always initiated at ultra-short latencies (Ϸ 85 ms) in the direction of grating motion. With elongated apertures, a later component was initiated 15-20 ms later in the direction of the terminator motion signals along the aperture's long axis. Amplitude of the later component was dependent upon the aperture's aspect ratio. Mean tracking direction at the end of the trial (135-175 ms after stimulus onset) was between the directions of the vector sum computed by integrating either terminator motion signals only or both grating and terminator motion signals. Introducing an elongated mask at the center of the "barber pole" did not affect the latency difference between early and later components, indicating that this latency shift was not due to foveal versus peripheral locations of 1D and 2D motion signals. Increasing the size of the foveal mask up to 90% of the stimulus area selectively reduced the strength of the grating motion signals and, consequently, the amplitude of the early component. Conversely, reducing the contrast of, or indenting the aperture's edges, selectively reduced the strength of terminator motion signals and, consequently, the amplitude of the later component. Latencies were never affected by these manipulations. These results tease apart an early component of tracking responses, driven by the grating motion signals and a later component, driven by the line-endings moving at the intersection between grating and aperture's borders. These results support the hypothesis of a parallel processing of 1D and 2D motion signals with different temporal dynamics.

show abstract

“…The exact combinations of grating frequency and speed will produce differences in apparent movement. However, Power and Moulden (1992) have reported that during a 1 min observation period the motion was judged to be along an aperture when the aperture was 1 deg or less in width and 8 deg in length. At 4 deg in width the motion became more ambiguous, with motion along the aperture being reported about 60% of the time.…”

Section: Introductionmentioning

confidence: 97%

Tests of the Dipole Model of Perceived Movement in Apertures

Power

1993

Perception

Self Cite

View full text Add to dashboard Cite

Power and Moulden (1992) have proposed a dipole model to account for the apparent movement of gratings in apertures. This includes movement orthogonal to the orientation of the grating, and the barber pole illusion: the illusion that a grating drifting diagonally across a narrow aperture appears to be moving along it. The essence of the model is that movement is signalled by a large number of dipoles, of many orientations and lengths. These dipoles respond if, and only if, one end is stimulated, and then the other. Three experiments intended to test predictions from the model are reported here. In each case a horizontal grating drifted across an aperture and subjects fixated outside the aperture. In experiment 1 subjects fixated just above or below the aperture, and reported the motion aftereffect (MAE) shown by a set of test spots. As predicted by the model, the spots further from the fixation point showed a strong MAE. Experiment 2 combined both viewing conditions of experiment 1, so that test spots above and below the fixation point were viewed simultaneously. The predictions were confirmed, since test spots further from the fixation point exhibited a stronger MAE than test spots closer to the fixation point. In experiment 3 the fixation point in all conditions was below the aperture, and, as predicted, the MAE of a spot near the bottom of the aperture was diagonally upward, although stimulation was horizontal. Again, as predicted, the MAE of a spot in the middle of the aperture appeared to move horizontally. Finally, it was predicted that a test spot at the top of the aperture would appear to move diagonally downwards, but subjects were unable to report unequivocally the direction of motion, since the MAE was occurring too far from the fovea for clear vision. Overall, then, the predictions from the model were confirmed, although there are associated phenomena the model cannot as yet account for.

show abstract

Spatial Gating Effects on Judged Motion of Gratings in Apertures

Cited by 21 publications

References 14 publications

Integration of Contour and Terminator Signals in Visual Area MT of Alert Macaque

Integration of Contour and Terminator Signals in Visual Area MT of Alert Macaque

Temporal dynamics of motion integration for the initiation of tracking eye movements at ultra-short latencies

Tests of the Dipole Model of Perceived Movement in Apertures

Contact Info

Product

Resources

About