Pattern Motion Processing by MT Neurons

Many models of perceptually based decisions postulate that actions are initiated when accumulated sensory signals reach a threshold level of activity. These models have received considerable neurophysiological support from recordings of individual neurons while animals are engaged in motion discrimination tasks. These experiments have found that the activity of neurons in a particular visual area strongly associated with motion processing (MT), when pooled over hundreds of milliseconds, is sufficient to explain behavioral timing and performance. However, this level of pooling may be problematic for urgent perceptual decisions in which rapid detection dictates temporally precise integration. In this paper, we explore the physiological basis of one such task in which macaques detected brief (~70 ms) transients of coherent motion within ~240 ms. We find that a simple linear summation model based on realistic stimulus responses of as few as 40 correlated neurons can predict the reliability and timing of rapid motion detection. The model naturally reproduces a distinctive physiological relationship observed in rapid detection tasks in which the individual neurons with the most reliable stimulus responses are also the most predictive of impending behavioral choices. Remarkably, we observed this relationship across our simulated neuronal populations even when all neurons within the pool were weighted equally with respect to readout. These results demonstrate that small numbers of reliable sensory neurons can dominate perceptual judgments without any explicit reliability based weighting and are sufficient to explain the accuracy, latency, and temporal precision of rapid detection. NEW & NOTEWORTHY Computational and psychophysical models suggest that performance in many perceptual tasks may be based on the preferential sampling of reliable neurons. Recent studies of MT neurons during rapid motion detection, in which only those neurons with the most reliable sensory responses were strongly predictive of the animals’ decisions, seemingly support this notion. Here we show that a simple threshold model without explicit reliability biases can explain both the behavioral accuracy and precision of these detections and the distribution of sensory- and choice-related signals across neurons.

Download Full-text

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.

Download Full-text

Responses of MST neurons to plaid stimuli

Journal of Neurophysiology ◽

10.1152/jn.00338.2012 ◽

2013 ◽

Vol 110 (1) ◽

pp. 63-74 ◽

Cited By ~ 13

Author(s):

Farhan A. Khawaja ◽

Liu D. Liu ◽

Christopher C. Pack

Keyword(s):

Motion Processing ◽

Two Stage ◽

Mt Neurons ◽

V1 Neurons ◽

Motion Integration ◽

Medial Superior Temporal ◽

Retinal Input ◽

Third Stage ◽

Mst Neurons ◽

Velocity Selectivity

The estimation of motion information from retinal input is a fundamental function of the primate dorsal visual pathway. Previous work has shown that this function involves multiple cortical areas, with each area integrating information from its predecessors. Compared with neurons in the primary visual cortex (V1), neurons in the middle temporal (MT) area more faithfully represent the velocity of plaid stimuli, and the observation of this pattern selectivity has led to two-stage models in which MT neurons integrate the outputs of component-selective V1 neurons. Motion integration in these models is generally complemented by motion opponency, which refines velocity selectivity. Area MT projects to a third stage of motion processing, the medial superior temporal (MST) area, but surprisingly little is known about MST responses to plaid stimuli. Here we show that increased pattern selectivity in MST is associated with greater prevalence of the mechanisms implemented by two-stage MT models: Compared with MT neurons, MST neurons integrate motion components to a greater degree and exhibit evidence of stronger motion opponency. Moreover, when tested with more challenging unikinetic plaid stimuli, an appreciable percentage of MST neurons are pattern selective, while such selectivity is rare in MT. Surprisingly, increased motion integration is found in MST even for transparent plaid stimuli, which are not typically integrated perceptually. Thus the relationship between MST and MT is qualitatively similar to that between MT and V1, as repeated application of basic motion mechanisms leads to novel selectivities at each stage along the pathway.

Download Full-text

A role for terminators in motion processing by macaque MT neurons?

Journal of Vision ◽

10.1167/2.7.415 ◽

2010 ◽

Vol 2 (7) ◽

pp. 415-415 ◽

Cited By ~ 6

Author(s):

N. Majaj ◽

M. A. Smith ◽

A. Kohn ◽

W. Bair ◽

J. A. Movshon

Keyword(s):

Motion Processing ◽

Mt Neurons

Download Full-text

Pattern and component responses of primate MT neurons recorded with multi-contact electrodes, stimulated with 1D and 2D noise patterns.

10.1101/2021.12.23.474004 ◽

2021 ◽

Author(s):

Christian Quaia ◽

Incheol Kang ◽

Bruce G Cumming

Keyword(s):

Type I ◽

Motion Direction ◽

Middle Temporal ◽

Mt Neurons ◽

Aperture Problem ◽

The Past ◽

Cortex Area ◽

Pattern Motion ◽

Alternative Measures ◽

Contact Electrodes

Direction selective neurons in primary visual cortex (area V1) are affected by the aperture problem, i.e., they are only sensitive to motion orthogonal to their preferred orientation. A solution to this problem first emerges in the middle temporal (MT) area, where a subset of neurons (called pattern cells) combine motion information across multiple orientations and directions, becoming sensitive to pattern motion direction. These cells are expected to play a prominent role in subsequent neural processing, but they are intermixed with cells that behave like V1 cells (component cells), and others that do not clearly fall in either group. The picture is further complicated by the finding that cells that behave like pattern cells with one type of pattern, might behave like component cells for another. We recorded from macaque MT neurons using multi-contact electrodes while presenting both type I and unikinetic plaids, in which the components were 1D noise patterns. We found that the indices that have been used in the past to classify neurons as pattern or component cells work poorly when the properties of the stimulus are not optimized for the cell being recorded, as is always the case with multi-contact arrays. We thus propose alternative measures, which considerably ameliorate the problem, and allow us to gain insights in the signals carried by individual MT neurons. We conclude that arranging cells along a component-to-pattern continuum is an oversimplification, and that the signals carried by individual cells only make sense when embodied in larger populations.

Download Full-text

Implied Motion Activation in Cortical Area MT Can Be Explained by Visual Low-level Features

Journal of Cognitive Neuroscience ◽

10.1162/jocn.2010.21533 ◽

2011 ◽

Vol 23 (6) ◽

pp. 1533-1548 ◽

Cited By ~ 8

Author(s):

Jeannette A. M. Lorteije ◽

Nick E. Barraclough ◽

Tjeerd Jellema ◽

Mathijs Raemaekers ◽

Jacob Duijnhouwer ◽

...

Keyword(s):

Receptive Field ◽

Cortical Neurons ◽

Motion Processing ◽

Area Mt ◽

Noise Pattern ◽

Low Level ◽

Mt Neurons ◽

Implied Motion ◽

Preferred Direction ◽

Random Dot Patterns

To investigate form-related activity in motion-sensitive cortical areas, we recorded cell responses to animate implied motion in macaque middle temporal (MT) and medial superior temporal (MST) cortex and investigated these areas using fMRI in humans. In the single-cell studies, we compared responses with static images of human or monkey figures walking or running left or right with responses to the same human and monkey figures standing or sitting still. We also investigated whether the view of the animate figure (facing left or right) that elicited the highest response was correlated with the preferred direction for moving random dot patterns. First, figures were presented inside the cell's receptive field. Subsequently, figures were presented at the fovea while a dynamic noise pattern was presented at the cell's receptive field location. The results show that MT neurons did not discriminate between figures on the basis of the implied motion content. Instead, response preferences for implied motion correlated with preferences for low-level visual features such as orientation and size. No correlation was found between the preferred view of figures implying motion and the preferred direction for moving random dot patterns. Similar findings were obtained in a smaller population of MST cortical neurons. Testing human MT+ responses with fMRI further corroborated the notion that low-level stimulus features might explain implied motion activation in human MT+. Together, these results suggest that prior human imaging studies demonstrating animate implied motion processing in area MT+ can be best explained by sensitivity for low-level features rather than sensitivity for the motion implied by animate figures.

Download Full-text

Spatial and temporal limits of pattern motion analysis by mt neurons

Journal of Vision ◽

10.1167/8.6.229 ◽

2010 ◽

Vol 8 (6) ◽

pp. 229-229

Author(s):

R. D. Kumbhani ◽

Y. El-Shamayleh ◽

J. A. Movshon

Keyword(s):

Motion Analysis ◽

Mt Neurons ◽

Pattern Motion

Download Full-text

Visual motion processing in the anterior ectosylvian sulcus of the cat

Journal of Neurophysiology ◽

10.1152/jn.1996.76.2.895 ◽

1996 ◽

Vol 76 (2) ◽

pp. 895-907 ◽

Cited By ~ 59

Author(s):

J. W. Scannell ◽

F. Sengpiel ◽

M. J. Tovee ◽

P. J. Benson ◽

C. Blakemore ◽

...

Keyword(s):

Visual Area ◽

Motion Processing ◽

Published Data ◽

Anterior Ectosylvian Sulcus ◽

Temporal Area ◽

Middle Temporal ◽

Visual Motion Processing ◽

Pattern Motion ◽

Middle Temporal Area ◽

Component Motion

1. Neurons that are selectively sensitive to the direction of motion of elongated contours have been found in several cortical areas in many species. However, in the striate cortex of the cat and monkey, and the extrastriate posteromedial lateral suprasylvian visual area of the cat, such cells are generally component motion selective, signaling only the direction of movement orthogonal to the preferred orientation; a direction that is not necessarily the same as the motion of the entire pattern or texture of which the cell's preferred contour is part. The primate extrastriate middle temporal area is the only cortical region currently known to contain a substantial population of pattern-motion-selective cells that respond to the shared vector of motion of mixtures of contours. 2. From analyzing published data on the connectivity of the cat's cortex, we predicted that the anterior ectosylvian visual area (AEV), situated within the anterior ectosylvian sulcus, might be a higher-order motion processing area and thus likely to contain pattern-motion-selective neurons. This paper presents the results of a study on neuronal responses in AEV. 3. Ninety percent of AEV cells that responded strongly to drifting grating and/or plaid stimuli were directionally selective (directionality index > 0.5). For this group, the mean directionality index was 0.75. Moreover, 55% of these cells were unequivocally classified as pattern motion selective and only one neuron was classified as definitely component motion selective. Thus high-level pattern motion coding occurs in the cat extrastriate cortex and is not limited to the primate middle temporal area. 4. AEV contains a heterogeneous population of directionally selective cells. There was no clear relation between the degree of directional selectivity for plaids or gratings and the degree of selectivity for pattern motion or component motion. Nevertheless, 28% of the highly responsive cells were both more strongly modulated by plaids than gratings and more pattern motion selective than component motion selective. Such cells could correspond to a population of "selection units" signaling the salience of local motion information. 5. AEV lacks global retinotopic order but the preferred direction of motion of neurons (rather than axis of motion, as in the middle temporal area and the posteromedial lateral suprasylvian visual area) is mapped systematically across the cortex. Our data are compatible with AEV being a nonretinotopic, feature-mapped area in which cells representing similar parts of "motion space" are brought together on the cortical sheet.

Download Full-text

Population Anisotropy in Area MT Explains a Perceptual Difference Between Near and Far Disparity Motion Segmentation

Journal of Neurophysiology ◽

10.1152/jn.00725.2009 ◽

2011 ◽

Vol 105 (1) ◽

pp. 200-208 ◽

Cited By ~ 2

Author(s):

Finnegan J. Calabro ◽

Lucia M. Vaina

Keyword(s):

Visual Cues ◽

Visual Motion ◽

Population Distribution ◽

Normal Population ◽

Motion Processing ◽

Area Mt ◽

Temporal Area ◽

Motion Discrimination ◽

Mt Neurons ◽

Simulated Performance

Segmentation of the visual scene into relevant object components is a fundamental process for successfully interacting with our surroundings. Many visual cues, including motion and binocular disparity, support segmentation, yet the mechanisms using these cues are unclear. We used a psychophysical motion discrimination task in which noise dots were displaced in depth to investigate the role of segmentation through disparity cues in visual motion stimuli ( experiment 1). We found a subtle, but significant, bias indicating that near disparity noise disrupted the segmentation of motion more than equidistant far disparity noise. A control experiment showed that the near-far difference could not be attributed to attention ( experiment 2). To account for the near-far bias, we constructed a biologically constrained model using recordings from neurons in the middle temporal area (MT) to simulate human observers' performance on experiment 1. Performance of the model of MT neurons showed a near-disparity skew similar to that shown by human observers. To isolate the cause of the skew, we simulated performance of a model containing units derived from properties of MT neurons, using phase-modulated Gabor disparity tuning. Using a skewed-normal population distribution of preferred disparities, the model reproduced the elevated motion discrimination thresholds for near-disparity noise, whereas a skewed-normal population of phases (creating individually asymmetric units) did not lead to any performance skew. Results from the model suggest that the properties of neurons in area MT are computationally sufficient to perform disparity segmentation during motion processing and produce similar disparity biases as those produced by human observers.

Download Full-text

Binocular integration of pattern motion signals by MT neurons and by human observers

Journal of Vision ◽

10.1167/7.9.95 ◽

2010 ◽

Vol 7 (9) ◽

pp. 95-95 ◽

Cited By ~ 1

Author(s):

C. Tailby ◽

N. Majaj ◽

T. Movshon

Keyword(s):

Mt Neurons ◽

Pattern Motion

Download Full-text