Microstimulation of Cortical Area MT Affects Performance on a Visual Working Memory Task

2001 ◽  
Vol 85 (1) ◽  
pp. 187-196 ◽  
Author(s):  
James W. Bisley ◽  
Daniel Zaksas ◽  
Tatiana Pasternak
Keyword(s):  
Working Memory ◽  
Visual Motion ◽  
Memory Task ◽  
Stimulus Motion ◽  
Area Mt ◽  
Directional Information ◽  
Temporal Area ◽  
Mt Neurons ◽  
Directional Motion ◽  
Term Storage

We applied electrical stimulation to physiologically identified sites in macaque middle temporal area (MT) to examine its role in short-term storage of recently encoded information about stimulus motion. We used a behavioral task in which monkeys compared the directions of two moving random-dot stimuli, sample and test, separated by a 1.5-s delay. Four sample directions were used for each site, and the animals had to indicate whether the direction of motion in the sample was the same as or different to the direction of motion in the test. We found that the effect of stimulation of the same directional column in MT depended on the behavioral state of the animal. Although stimulation had strong effects when applied during the encoding and the storage components of the task, these effects were not equivalent. Stimulation applied during the presentation of the sample produced signals interpreted by the monkeys as directional motion. However, the same stimulation introduced during the period of storage no longer produced signals interpreted as unambiguous directional information. We conclude that the directional information used by the monkeys in the working memory task is likely to be provided by neurons in MT, and the use of this information appears to be dependent on the portion of the task during which stimulation was delivered. Finally, the disruptive effects of stimulation during the delay suggest that MT neurons not only participate in the encoding of visual motion information but also in its storage by either maintaining an active connection with the circuitry involved in storage or being an integral component of that circuitry.

Ventral intraparietal area of the macaque: anatomic location and visual response properties

1993 ◽  
Vol 69 (3) ◽  
pp. 902-914 ◽  
Author(s):  
C. L. Colby ◽  
J. R. Duhamel ◽  
M. E. Goldberg
Keyword(s):  
Visual Motion ◽  
Visual Response ◽  
Intraparietal Sulcus ◽  
Stimulus Motion ◽  
Area Mt ◽  
Temporal Area ◽  
Response Properties ◽  
Preferred Direction ◽  
The Face ◽  
Ventral Intraparietal Area

1. The middle temporal area (MT) projects to the intraparietal sulcus in the macaque monkey. We describe here a discrete area in the depths of the intraparietal sulcus containing neurons with response properties similar to those reported for area MT. We call this area the physiologically defined ventral intraparietal area, or VIP. In the present study we recorded from single neurons in VIP of alert monkeys and studied their visual and oculomotor response properties. 2. Area VIP has a high degree of selectivity for the direction of a moving stimulus. In our sample 72/88 (80%) neurons responded at least twice as well to a stimulus moving in the preferred direction compared with a stimulus moving in the null direction. The average response to stimuli moving in the preferred direction was 9.5 times as strong as the response to stimuli moving in the opposite direction, as compared with 10.9 times as strong for neurons in area MT. 3. Many neurons were also selective for speed of stimulus motion. Quantitative data from 25 neurons indicated that the distribution of preferred speeds ranged from 10 to 320 degrees/s. The degree of speed tuning was on average twice as broad as that reported for area MT. 4. Some neurons (22/41) were selective for the distance at which a stimulus was presented, preferring a stimulus of equivalent visual angle and luminance presented near (within 20 cm) or very near (within 5 cm) the face. These neurons maintained their preference for near stimuli when tested monocularly, suggesting that visual cues other than disparity can support this response. These neurons typically could not be driven by small spots presented on the tangent screen (at 57 cm). 5. Some VIP neurons responded best to a stimulus moving toward the animal. The absolute direction of visual motion was not as important for these cells as the trajectory of the stimulus: the best stimulus was one moving toward a particular point on the face from any direction. 6. VIP neurons were not active in relation to saccadic eye movements. Some neurons (10/17) were active during smooth pursuit of a small target. 7. The predominance of direction and speed selectivity in area VIP suggests that it, like other visual areas in the dorsal stream, may be involved in the analysis of visual motion.

scholarly journals The contribution of area MT to visual motion perception depends on training

2016 ◽  
Author(s):  
Liu D. Liu ◽  
Christopher C. Pack
Keyword(s):  
Motion Perception ◽  
Visual Motion ◽  
Brain Regions ◽  
Stimulus Motion ◽  
Area Mt ◽  
Temporal Area ◽  
Visual Motion Perception ◽  
Motion Discrimination ◽  
Cortex Area ◽  
Training History

SummaryPerceptual decisions require the transformation of raw sensory inputs into cortical representations suitable for stimulus discrimination. One of the best-known examples of this transformation involves the middle temporal area (MT) of the primate visual cortex. Area MT provides a robust representation of stimulus motion, and previous work has shown that it contributes causally to performance on motion discrimination tasks. Here we report that the strength of this contribution can be highly plastic: Depending on the recent training history, pharmacological inactivation of MT can severely impair motion discrimination, or it can have little detectable influence. Similarly, depending on training, microstimulation can bias motion perception or simply introduce noise. Further analysis of neural and behavioral data suggests that training shifts the readout of motion information between MT and lower-level cortical areas. These results show that the contribution of individual brain regions to conscious perception can shift flexibly depending on sensory experience.

A relationship between behavioral choice and the visual responses of neurons in macaque MT

1996 ◽  
Vol 13 (1) ◽  
pp. 87-100 ◽  
Author(s):  
K. H. Britten ◽  
W. T. Newsome ◽  
M. N. Shadlen ◽  
S. Celebrini ◽  
J. A. Movshon
Keyword(s):  
Visual Motion ◽  
Visual Stimulation ◽  
Visual Responses ◽  
Stimulus Motion ◽  
Area Mt ◽  
Motion Sensitivity ◽  
Behavioral Choice ◽  
Mt Neurons ◽  
Preferred Direction ◽  
The Relationship

AbstractWe have previously documented the exquisite motion sensitivity of neurons in extrastriate area MT by studying the relationship between their responses and the direction and strength of visual motion signals delivered to their receptive fields. These results suggested that MT neurons might provide the signals supporting behavioral choice in visual discrimination tasks. To approach this question from another direction, we have now studied the relationship between the discharge of MT neurons and behavioral choice, independently of the effects of visual stimulation. We found that trial-to-trial variability in neuronal signals was correlated with the choices the monkey made. Therefore, when a directionally selective neuron in area MT fires more vigorously, the monkey is more likely to make a decision in favor of the preferred direction of the cell. The magnitude of the relationship was modest, on average, but was highly significant across a sample of 299 cells from four monkeys. The relationship was present for all stimuli (including those without a net motion signal), and for all but the weakest responses. The relationship was reduced or eliminated when the demands of the task were changed so that the directional signal carried by the cell was less informative. The relationship was evident within 50 ms of response onset, and persisted throughout the stimulus presentation. On average, neurons that were more sensitive to weak motion signals had a stronger relationship to behavior than those that were less sensitive. These observations are consistent with the idea that neuronal signals in MT are used by the monkey to determine the direction of stimulus motion. The modest relationship between behavioral choice and the discharge of any one neuron, and the prevalence of the relationship across the population, make it likely that signals from many neurons are pooled to form the data on which behavioral choices are based.

Distinct Nature of Directional Signals Among Parietal Cortical Areas During Visual Guidance

2002 ◽  
Vol 88 (4) ◽  
pp. 1777-1790 ◽  
Author(s):  
Emad N. Eskandar ◽  
John A. Assad
Keyword(s):  
Visual Motion ◽  
Hand Movement ◽  
Direction Selectivity ◽  
Visually Guided ◽  
Stimulus Motion ◽  
Directional Information ◽  
Temporal Area ◽  
Medial Superior Temporal ◽  
Direction Of Movement ◽  
Mst Neurons

We examined neuronal signals in the monkey medial superior temporal area (MST), the medial intraparietal area (MIP), and the lateral intraparietal area (LIP) during visually guided hand movements. Two animals were trained to use a joystick to guide a spot to a target. Many neurons responded in a direction-selective manner in this guidance task. We tested whether the direction selectivity depended on the direction of the stimulus spot or the direction of the hand movement. First, in some trials, the moving spot disappeared transiently. Second, the mapping between the hand direction and the spot direction was reversed on alternate blocks of trials. Third, we recorded the spot's movement while the animals moved the joystick and then played back that movement while the animals fixated without moving the joystick. Neurons in the three parietal areas conveyed distinct directional information. MST neurons were active and directional only on visible trials in both joystick-movement mode and playback mode and were not affected by the direction of hand movement. MIP neurons were mainly directional with respect to the hand movement, although some MIP neurons were also selective for stimulus direction. MIP neurons were much less active in playback mode. LIP neurons were active and directional in both joystick-movement mode and playback mode. Directional signals in LIP were unrelated to planning saccades. The selectivity of LIP neurons also became evident hundreds of milliseconds before the start of movement. Since the direction of movement was consistent throughout a block of trials, these signals could provide a prediction of the upcoming direction of motion. We tested this by alternating blocks of trials in which the direction was consistent or randomized. The direction selectivity developed earlier on trials in which the upcoming direction could be predicted. These results suggest that LIP neurons combine “bottom-up” visual motion signals with extraretinal, predictive signals about stimulus motion.

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

2011 ◽  
Vol 105 (1) ◽  
pp. 200-208 ◽  
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.

Motion Information Is Spatially Localized in a Visual Working-Memory Task

2001 ◽  
Vol 86 (2) ◽  
pp. 912-921 ◽  
Author(s):  
Daniel Zaksas ◽  
James W. Bisley ◽  
Tatiana Pasternak
Keyword(s):  
Working Memory ◽  
Receptive Field ◽  
Visual Working Memory ◽  
Memory Task ◽  
Spatial Separation ◽  
Field Size ◽  
Retinal Eccentricity ◽  
Stimulus Motion ◽  
Area Mt ◽  
Receptive Field Size

We asked if the information about stimulus motion used in a visual working-memory task is localized in space. Monkeys compared the directions of two moving random-dot stimuli, sample and test, separated by a temporal delay and reported whether the stimuli moved in the same or in different directions. By presenting the two comparison stimuli in separate locations in the visual field, we determined whether information about stimulus direction was spatially localized during the storage and retrieval/comparison components of the task. Two psychophysical measures of direction discrimination provided nearly identical estimates of the critical spatial separation between sample and test stimuli that lead to a loss in threshold. Direction range thresholds measured with dot stimuli consisting of a range of local directional vectors were affected by spatial separation when a random-motion mask was introduced during the delay into the location of the upcoming test. The selective masking at the test location suggests that the information about the remembered direction was localized and available at that location. Direction difference thresholds, measured with coherently moving random dots, were also affected by separation between the two comparison stimuli. The separation at which performance was affected in both tasks increased with retinal eccentricity in parallel with the increase in receptive-field size in neurons in cortical area MT. The loss with transfer of visual information between different spatial locations suggests a contribution of cortical areas with localized receptive fields to the performance of the memory task. The similarity in the spatial scale of the storage mechanism derived psychophysically and the receptive field size of neurons in area MT suggest that MT neurons are central to this task.

Area MT Neurons Respond to Visual Motion Distant From Their Receptive Fields

2005 ◽  
Vol 94 (6) ◽  
pp. 4156-4167 ◽  
Author(s):  
Daniel Zaksas ◽  
Tatiana Pasternak
Keyword(s):  
Time Course ◽  
Visual Motion ◽  
Cognitive Task ◽  
Receptive Fields ◽  
Direction Selectivity ◽  
Task Demands ◽  
Visual Signals ◽  
Area Mt ◽  
Mt Neurons ◽  
Stimulus Offset

Neurons in cortical area MT have localized receptive fields (RF) representing the contralateral hemifield and play an important role in processing visual motion. We recorded the activity of these neurons during a behavioral task in which two monkeys were required to discriminate and remember visual motion presented in the ipsilateral hemifield. During the task, the monkeys viewed two stimuli, sample and test, separated by a brief delay and reported whether they contained motion in the same or in opposite directions. Fifty to 70% of MT neurons were activated by the motion stimuli presented in the ipsilateral hemifield at locations far removed from their classical receptive fields. These responses were in the form of excitation or suppression and were delayed relative to conventional MT responses. Both excitatory and suppressive responses were direction selective, but the nature and the time course of their directionality differed from the conventional excitatory responses recorded with stimuli in the RF. Direction selectivity of the excitatory remote response was transient and early, whereas the suppressive response developed later and persisted after stimulus offset. The presence or absence of these unusual responses on error trials, as well as their magnitude, was affected by the behavioral significance of stimuli used in the task. We hypothesize that these responses represent top-down signals from brain region(s) accessing information about stimuli in the entire visual field and about the behavioral state of the animal. The recruitment of neurons in the opposite hemisphere during processing of behaviorally relevant visual signals reveals a mechanism by which sensory processing can be affected by cognitive task demands.

scholarly journals Feature attention for binocular disparity in primate area MT depends on tuning strength

2015 ◽  
Vol 113 (5) ◽  
pp. 1545-1555 ◽  
Author(s):  
Douglas A. Ruff ◽  
Richard T. Born
Keyword(s):  
Binocular Disparity ◽  
Receptive Fields ◽  
Sensory Information ◽  
Neuronal Population ◽  
Area Mt ◽  
Temporal Area ◽  
Mt Neurons ◽  
Feature Attention ◽  
The Difference ◽  
The Relationship

Attending to a stimulus modulates the responses of sensory neurons that represent features of that stimulus, a phenomenon named “feature attention.” For example, attending to a stimulus containing upward motion enhances the responses of upward-preferring direction-selective neurons in the middle temporal area (MT) and suppresses the responses of downward-preferring neurons, even when the attended stimulus is outside of the spatial receptive fields of the recorded neurons (Treue S, Martinez-Trujillo JC. Nature 399: 575–579, 1999). This modulation renders the representation of sensory information across a neuronal population more selective for the features present in the attended stimulus (Martinez-Trujillo JC, Treue S. Curr Biol 14: 744–751, 2004). We hypothesized that if feature attention modulates neurons according to their tuning preferences, it should also be sensitive to their tuning strength, which is the magnitude of the difference in responses to preferred and null stimuli. We measured how the effects of feature attention on MT neurons in rhesus monkeys ( Macaca mulatta) depended on the relationship between features—in our case, direction of motion and binocular disparity—of the attended stimulus and a neuron's tuning for those features. We found that, as for direction, attention to stimuli containing binocular disparity cues modulated the responses of MT neurons and that the magnitude of the modulation depended on both a neuron's tuning preferences and its tuning strength. Our results suggest that modulation by feature attention may depend not just on which features a neuron represents but also on how well the neuron represents those features.

Motion Mechanisms in Macaque MT

2005 ◽  
Vol 93 (5) ◽  
pp. 2908-2921 ◽  
Author(s):  
Bart Krekelberg ◽  
Thomas D. Albright
Keyword(s):  
Visual Motion ◽  
Dynamic Range ◽  
Gain Control ◽  
Competitive Interaction ◽  
Energy Model ◽  
Temporal Area ◽  
Motion Patterns ◽  
Mt Neurons ◽  
Motion Energy ◽  
Energy Components

The macaque middle temporal area (MT) is exquisitely sensitive to visual motion and there is a large amount of evidence that neural activity in MT is tightly correlated with the perception of motion. The mechanisms by which MT neurons achieve their directional selectivity, however, have received considerably less attention. We investigated the motion–energy model as a description of motion mechanisms in macaque MT. We first confirmed one of the predictions of the motion–energy model; macaques—just like humans—perceive a reversed direction of motion when a stimulus reverses contrast with every displacement (reverse-phi). This reversal of perceived direction had a clear correlate in the neural responses of MT cells, which were predictive of the monkey's behavioral decisions. Second, we investigated how multiple motion–energy components are combined. Psychophysical data have been used to argue that motion–energy components representing opposite directions are subtracted from each other. Our data show, however, that the interactions among motion–energy components are more complex. In particular, we found that the influence of a given component on the response to a stimulus consisting of multiple components depends on factors other than the response to that component alone. This suggests that there are subthreshold nonlinear interactions among multiple motion–energy components; these could take place within MT or in earlier stages of the motion network such as V1. We propose a model that captures the complexity of these component interactions by means of a competitive interaction among the components. This provides a better description of the MT responses than the subtractive motion opponency envisaged in the motion–energy model, even when the latter is combined with a gain-control mechanism. The competitive interaction extends the dynamic range of the cells and allows them to provide information on more subtle changes in motion patterns, including changes that are not purely directional.

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