Shared attentional resources for global and local motion processing

Background: To study motion perception, a stimulus consisting of a field of small, moving dots is often used. Generally, some of the dots coherently move in the same direction (signal) while the rest move randomly (noise). A percept of global coherent motion (CM) results when many different local motion signals are combined. CM computation is a complex process that requires the integrity of the middle-temporal area (MT/V5) and there is evidence that increasing the number of dots presented in the stimulus makes such computation more efficient. Objective: In this study, we explored whether anodal direct current stimulation (tDCS) over MT/V5 would increase individual performance in a CM task at a low signal-to-noise ratio (SNR, i.e. low percentage of coherent dots) and with a target consisting of a large number of moving dots (high dot numerosity, e.g. >250 dots) with respect to low dot numerosity (<60 dots), indicating that tDCS favour the integration of local motion signal into a single global percept (global motion). Method: Participants were asked to perform a CM detection task (two-interval forced-choice, 2IFC) while they received anodal, cathodal, or sham stimulation on three different days. Results: Our findings showed no effect of cathodal tDCS with respect to the sham condition. Instead, anodal tDCS improves performance, but mostly when dot numerosity is high (>400 dots) to promote efficient global motion processing. Conclusions: The present study suggests that tDCS may be used under appropriate stimulus conditions (low SNR and high dot numerosity) to boost the global motion processing efficiency, and may be useful to empower clinical protocols to treat visual deficits.

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The direction after-effect is a global motion phenomenon

Royal Society Open Science ◽

10.1098/rsos.190114 ◽

2019 ◽

Vol 6 (3) ◽

pp. 190114

Author(s):

William Curran ◽

Lee Beattie ◽

Delfina Bilello ◽

Laura A. Coulter ◽

Jade A. Currie ◽

...

Keyword(s):

Neural Mechanisms ◽

Motion Processing ◽

Global Motion ◽

Local Motion ◽

Motion Direction ◽

Processing Level ◽

True Motion ◽

Pattern Motion ◽

Moving Stimulus ◽

After Effect

Prior experience influences visual perception. For example, extended viewing of a moving stimulus results in the misperception of a subsequent stimulus's motion direction—the direction after-effect (DAE). There has been an ongoing debate regarding the locus of the neural mechanisms underlying the DAE. We know the mechanisms are cortical, but there is uncertainty about where in the visual cortex they are located—at relatively early local motion processing stages, or at later global motion stages. We used a unikinetic plaid as an adapting stimulus, then measured the DAE experienced with a drifting random dot test stimulus. A unikinetic plaid comprises a static grating superimposed on a drifting grating of a different orientation. Observers cannot see the true motion direction of the moving component; instead they see pattern motion running parallel to the static component. The pattern motion of unikinetic plaids is encoded at the global processing level—specifically, in cortical areas MT and MST—and the local motion component is encoded earlier. We measured the direction after-effect as a function of the plaid's local and pattern motion directions. The DAE was induced by the plaid's pattern motion, but not by its component motion. This points to the neural mechanisms underlying the DAE being located at the global motion processing level, and no earlier than area MT.

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The movement of motion-defined contours can bias perceived position

Biology Letters ◽

10.1098/rsbl.2008.0622 ◽

2009 ◽

Vol 5 (2) ◽

pp. 270-273 ◽

Cited By ~ 4

Author(s):

Szonya Durant ◽

Johannes M Zanker

Keyword(s):

Visual Processing ◽

Spatial Location ◽

Motion Processing ◽

Local Motion ◽

Motion Direction ◽

Motion Patterns ◽

Object Properties ◽

Accurate Position ◽

Processing Steps ◽

Over Time

Illusory position shifts induced by motion suggest that motion processing can interfere with perceived position. This may be because accurate position representation is lost during successive visual processing steps. We found that complex motion patterns, which can only be extracted at a global level by pooling and segmenting local motion signals and integrating over time, can influence perceived position. We used motion-defined Gabor patterns containing motion-defined boundaries, which themselves moved over time. This ‘motion-defined motion’ induced position biases of up to 0.5°, much larger than has been found with luminance-defined motion. The size of the shift correlated with how detectable the motion-defined motion direction was, suggesting that the amount of bias increased with the magnitude of this complex directional signal. However, positional shifts did occur even when participants were not aware of the direction of the motion-defined motion. The size of the perceptual position shift was greatly reduced when the position judgement was made relative to the location of a static luminance-defined square, but not eliminated. These results suggest that motion-induced position shifts are a result of general mechanisms matching dynamic object properties with spatial location.

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Global and local motion descriptions for human action recognition

International Conference on Electrical & Computer Engineering (ICECE 2010) ◽

10.1109/icelce.2010.5700784 ◽

2010 ◽

Author(s):

Irine Parvin ◽

Mohiuddin Ahmad

Keyword(s):

Action Recognition ◽

Human Action Recognition ◽

Human Action ◽

Local Motion ◽

Global And Local

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Detection of Global and Local Motion Changes in Human Crowds

IEEE Transactions on Circuits and Systems for Video Technology ◽

10.1109/tcsvt.2016.2596199 ◽

2017 ◽

Vol 27 (3) ◽

pp. 603-612 ◽

Cited By ~ 13

Author(s):

Igor R. de Almeida ◽

Vinicius J. Cassol ◽

Norman I. Badler ◽

Soraia Raupp Musse ◽

Claudio Rosito Jung

Keyword(s):

Local Motion ◽

Global And Local

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Local and Global Representations of Velocity: Transparency, Opponency, and Global Direction Perception

Perception ◽

10.1068/p260995 ◽

1997 ◽

Vol 26 (8) ◽

pp. 995-1010 ◽

Cited By ~ 33

Author(s):

Oliver Braddick

Keyword(s):

Visual Motion ◽

Multiple Scales ◽

Human Subjects ◽

Motion Processing ◽

Spatial Integration ◽

Local Motion ◽

Directional Information ◽

Object Based ◽

Transparent Display ◽

Winner Take All

Human subjects can perceive global motion or motions in displays containing diverse local motions, implying representation of velocity at multiple scales. The phenomena of flexible global direction judgments, and especially of motion transparency, also raise the issue of whether the representation of velocity at any one scale is single-valued or multi-valued. A new performance-based measure of transparency confirms that the visual system represents directional information for each component of a transparent display. However, results with the locally paired random-dot display introduced by Qian et al, show that representations of multiple velocities do not coexist at the finest spatial scale of motion analysis. Functionally distinct scales of motion processing may be associated with (i) local motion detectors which show a strong winner-take-all interaction; (ii) spatial integration of local signals to disambiguate velocity; (iii) selection of reliable velocity signals as proposed in the model of Nowlan and Sejnowski; (iv) object-based or surface-based representations that are not necessarily organised in a fixed spatial matrix. These possibilities are discussed in relation to the neurobiological organisation of the visual motion pathway.

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Alterations to global but not local motion processing in long-term ecstasy (MDMA) users

Psychopharmacology ◽

10.1007/s00213-014-3431-7 ◽

2014 ◽

Vol 231 (13) ◽

pp. 2611-2622 ◽

Cited By ~ 2

Author(s):

Claire White ◽

John Brown ◽

Mark Edwards

Keyword(s):

Motion Processing ◽

Local Motion

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Population receptive field estimates for motion-defined stimuli

10.1101/435735 ◽

2018 ◽

Cited By ~ 1

Author(s):

Anna E. Hughes ◽

John A. Greenwood ◽

Nonie J. Finlayson ◽

D. Samuel Schwarzkopf

Keyword(s):

Receptive Field ◽

Large Field ◽

Motion Processing ◽

Global Motion ◽

Local Motion ◽

Visual Hierarchy ◽

Retinotopic Maps ◽

Motion Condition ◽

Early Visual Cortex ◽

Kinetic Boundary

AbstractThe processing of motion changes throughout the visual hierarchy, from spatially restricted ‘local motion’ in early visual cortex to more complex large-field ‘global motion’ at later stages. Here we used functional magnetic resonance imaging (fMRI) to examine spatially selective responses in these areas related to the processing of random-dot stimuli defined by differences in motion. We used population receptive field (pRF) analyses to map retinotopic cortex using bar stimuli comprising coherently moving dots. In the first experiment, we used three separate background conditions: no background dots (dot-defined bar-only), dots moving coherently in the opposite direction to the bar (kinetic boundary) and dots moving incoherently in random directions (global motion). Clear retinotopic maps were obtained for the bar-only and kinetic-boundary conditions across visual areas V1-V3 and in higher dorsal areas. For the global-motion condition, retinotopic maps were much weaker in early areas and became clear only in higher areas, consistent with the emergence of global-motion processing throughout the visual hierarchy. However, in a second experiment we demonstrate that this pattern is not specific to motion-defined stimuli, with very similar results for a transparent-motion stimulus and a bar defined by a static low-level property (dot size) that should have driven responses particularly in V1. We further exclude explanations based on stimulus visibility by demonstrating that the observed differences in pRF properties do not follow the ability of observers to localise or attend to these bar elements. Rather, our findings indicate that dorsal extrastriate retinotopic maps may primarily be determined by the visibility of the neural responses to the bar relative to the background response (i.e. neural signal-to-noise ratios) and suggests that claims about stimulus selectivity from pRF experiments must be interpreted with caution.

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