scholarly journals Effect of feature-selective attention on neuronal responses in macaque area MT

2012 ◽  
Vol 107 (5) ◽  
pp. 1530-1543 ◽  
Author(s):  
X. Chen ◽  
K.-P. Hoffmann ◽  
T. D. Albright ◽  
A. Thiele
Keyword(s):  
Selective Attention ◽  
Firing Rate ◽  
Visual Processing ◽  
Sine Wave ◽  
Stimulus Dimension ◽  
Extrastriate Cortex ◽  
Motion Direction ◽  
Area Mt ◽  
Mt Neurons ◽  
Feature Based

Attention influences visual processing in striate and extrastriate cortex, which has been extensively studied for spatial-, object-, and feature-based attention. Most studies exploring neural signatures of feature-based attention have trained animals to attend to an object identified by a certain feature and ignore objects/displays identified by a different feature. Little is known about the effects of feature-selective attention, where subjects attend to one stimulus feature domain (e.g., color) of an object while features from different domains (e.g., direction of motion) of the same object are ignored. To study this type of feature-selective attention in area MT in the middle temporal sulcus, we trained macaque monkeys to either attend to and report the direction of motion of a moving sine wave grating (a feature for which MT neurons display strong selectivity) or attend to and report its color (a feature for which MT neurons have very limited selectivity). We hypothesized that neurons would upregulate their firing rate during attend-direction conditions compared with attend-color conditions. We found that feature-selective attention significantly affected 22% of MT neurons. Contrary to our hypothesis, these neurons did not necessarily increase firing rate when animals attended to direction of motion but fell into one of two classes. In one class, attention to color increased the gain of stimulus-induced responses compared with attend-direction conditions. The other class displayed the opposite effects. Feature-selective activity modulations occurred earlier in neurons modulated by attention to color compared with neurons modulated by attention to motion direction. Thus feature-selective attention influences neuronal processing in macaque area MT but often exhibited a mismatch between the preferred stimulus dimension (direction of motion) and the preferred attention dimension (attention to color).

scholarly journals Spatial precision of population activity in primate area MT

2015 ◽  
Vol 114 (2) ◽  
pp. 869-878 ◽  
Author(s):  
Spencer C. Chen ◽  
John W. Morley ◽  
Samuel G. Solomon
Keyword(s):  
Neural Activity ◽  
Visual Processing ◽  
Receptive Fields ◽  
Object Motion ◽  
Spatial Position ◽  
Multielectrode Arrays ◽  
Visual World ◽  
Population Activity ◽  
Area Mt ◽  
Mt Neurons

The middle temporal (MT) area is a cortical area integral to the “where” pathway of primate visual processing, signaling the movement and position of objects in the visual world. The receptive field of a single MT neuron is sensitive to the direction of object motion but is too large to signal precise spatial position. Here, we asked if the activity of MT neurons could be combined to support the high spatial precision required in the where pathway. With the use of multielectrode arrays, we recorded simultaneously neural activity at 24–65 sites in area MT of anesthetized marmoset monkeys. We found that although individual receptive fields span more than 5° of the visual field, the combined population response can support fine spatial discriminations (<0.2°). This is because receptive fields at neighboring sites overlapped substantially, and changes in spatial position are therefore projected onto neural activity in a large ensemble of neurons. This fine spatial discrimination is supported primarily by neurons with receptive fields flanking the target locations. Population performance is degraded (by 13–22%) when correlations in neural activity are ignored, further reflecting the contribution of population neural interactions. Our results show that population signals can provide high spatial precision despite large receptive fields, allowing area MT to represent both the motion and the position of objects in the visual world.

scholarly journals Task-specific, dimension-based attentional shaping of motion processing in monkey area MT

2017 ◽  
Vol 118 (3) ◽  
pp. 1542-1555 ◽  
Author(s):  
Bastian Schledde ◽  
F. Orlando Galashan ◽  
Magdalena Przybyla ◽  
Andreas K. Kreiter ◽  
Detlef Wegener
Keyword(s):  
Visual Processing ◽  
Visual Information ◽  
Color Change ◽  
Visual Stimulation ◽  
Motion Processing ◽  
Motion Direction ◽  
Area Mt ◽  
Baseline Activity ◽  
Specific Dimension ◽  
Feature Dimension

Nonspatially selective attention is based on the notion that specific features or objects in the visual environment are effectively prioritized in cortical visual processing. Feature-based attention (FBA), in particular, is a well-studied process that dynamically and selectively addresses neurons preferentially processing the attended feature attribute (e.g., leftward motion). In everyday life, however, behavior may require high sensitivity for an entire feature dimension (e.g., motion), but experimental evidence for a feature dimension-specific attentional modulation on a cellular level is lacking. Therefore, we investigated neuronal activity in macaque motion-selective mediotemporal area (MT) in an experimental setting requiring the monkeys to detect either a motion change or a color change. We hypothesized that neural activity in MT is enhanced when the task requires perceptual sensitivity to motion. In line with this, we found that mean firing rates were higher in the motion task and that response variability and latency were lower compared with values in the color task, despite identical visual stimulation. This task-specific, dimension-based modulation of motion processing emerged already in the absence of visual input, was independent of the relation between the attended and stimulating motion direction, and was accompanied by a spatially global reduction of neuronal variability. The results provide single-cell support for the hypothesis of a feature dimension-specific top-down signal emphasizing the processing of an entire feature class. NEW & NOTEWORTHY Cortical processing serving visual perception prioritizes information according to current task requirements. We provide evidence in favor of a dimension-based attentional mechanism addressing all neurons that process visual information in the task-relevant feature domain. Behavioral tasks required monkeys to attend either color or motion, causing modulations of response strength, variability, latency, and baseline activity of motion-selective monkey area MT neurons irrespective of the attended motion direction but specific to the attended feature dimension.

scholarly journals Constraints on the Source of Short-Term Motion Adaptation in Macaque Area MT. I. The Role of Input and Intrinsic Mechanisms

2002 ◽  
Vol 88 (1) ◽  
pp. 354-369 ◽  
Author(s):  
Nicholas J. Priebe ◽  
Mark M. Churchland ◽  
Stephen G. Lisberger
Keyword(s):  
Firing Rate ◽  
Time Course ◽  
Receptive Fields ◽  
Visual Space ◽  
Extrastriate Cortex ◽  
Target Velocity ◽  
Short Term ◽  
Cellular Mechanisms ◽  
Area Mt ◽  
Short Term Adaptation

Neurons in area MT, a motion-sensitive area of extrastriate cortex, respond to a step of target velocity with a transient-sustained firing pattern. The transition from a high initial firing rate to a lower sustained rate occurs over a time course of 20–80 ms and is considered a form of short-term adaptation. The present paper asks whether adaptation is due to input-specific mechanisms such as short-term synaptic depression or if it results from intrinsic cellular mechanisms such as spike-rate adaptation. We assessed the contribution of input-specific mechanisms by using a condition/test paradigm to measure the spatial scale of adaptation. Conditioning and test stimuli were placed within MT receptive fields but were spatially segregated so that the two stimuli would activate different populations of inputs from the primary visual cortex (V1). Conditioning motion at one visual location caused a reduction of the transient firing to subsequent test motion at a second location. The adaptation field, estimated as the region of visual space where conditioning motion caused adaptation, was always larger than the MT receptive field. Use of the same stimulus configuration while recording from direction-selective neurons in V1 failed to demonstrate either adaptation or the transient-sustained response pattern that is the signature of short-term adaptation in MT. We conclude that the shift from transient to sustained firing in MT cells does not result from an input-specific mechanism applied to inputs from V1 because it operates over a wider range of the visual field than is covered by receptive fields of V1 neurons. We used a direct analysis of MT neuron spike trains for many repetitions of the same motion stimulus to assess the contribution to adaptation of intrinsic cellular mechanisms related to spiking. On a trial-by-trial basis, there was no correlation between number of spikes in the transient interval and the interval immediately after the transient period. This is opposite the prediction that there should be a correlation if spikes cause adaptation directly. Further, the transient was suppressed or extinguished, not delayed, in trials in which the neuron emitted zero spikes during the interval that showed a transient in average firing rate. We conclude that the transition from transient to sustained firing in neurons in area MT is caused by mechanisms that are neither input-specific nor controlled by the spiking of the adapting neuron. We propose that the short-term adaptation observed in area MT emerges from the intracortical circuit within MT.

Effect of Spatial Attention on the Responses of Area MT Neurons

1999 ◽  
Vol 81 (4) ◽  
pp. 1783-1794 ◽  
Author(s):  
Eyal Seidemann ◽  
William T. Newsome
Keyword(s):  
Spatial Attention ◽  
Spatial Location ◽  
Stimulus Onset ◽  
The Other ◽  
Extrastriate Cortex ◽  
Stimulus Motion ◽  
Area Mt ◽  
Mt Neurons ◽  
Preferred Direction ◽  
Stimulus Offset

Effect of spatial attention on the responses of area MT neurons. This study examines the influence of spatial attention on the responses of neurons in the middle temporal visual area (MT or V5) of extrastriate cortex. Two monkeys were trained to perform a direction-discrimination task. On each trial, two apertures of random-dot stimuli appeared simultaneously at two spatially separated locations; the monkeys were required to discriminate the direction of stimulus motion at one location while ignoring the stimulus at the other location. After extensive training, we recorded the responses of MT neurons in two configurations: 1) Both apertures placed “within” the neuron’s receptive field (RF) and 2) one aperture covering the RF while the other was presented at a “remote” location. For each unit we compared the responses to identical stimulus displays when the monkey was instructed to attend to one or the other aperture. The responses of MT neurons were 8.7% stronger, on average, when the monkey attended to the spatial location that contained motion in the “preferred” direction. Attentional effects were equal, on average, in the within RF and remote configurations. The attentional modulations began ∼300 ms after stimulus onset, gradually increased throughout the trial, and peaked near stimulus offset. An analysis of the neuronal responses on error trials suggests that the monkeys failed to attend to the appropriate spatial location on these trials. The relatively weak attentional effects that we observed contrast strikingly with recent results of Treue and Maunsell, who demonstrated very strong attentional modulations (median effect >80%) in MT in a task that shares many features with ours. Our results suggest that spatial attention alone is not sufficient to induce strong attentional effects in MT even when two competing motion stimuli appear within the RF of the recorded neuron. The difference between our results and those of Treue and Maunsell suggests that the magnitude of the attentional effects in MT may depend critically on how attention is directed to a particular stimulus and on the precise demands of the task.

scholarly journals Responses of neurons in macaque MT to unikinetic plaids

2019 ◽  
Vol 122 (5) ◽  
pp. 1937-1945 ◽  
Author(s):  
Pascal Wallisch ◽  
J. Anthony Movshon
Keyword(s):  
Sine Wave ◽  
Direction Selectivity ◽  
Visual Signals ◽  
Area Mt ◽  
Mt Neurons ◽  
Component Cell ◽  
Intersection Of Constraints ◽  
The Individual ◽  
Sine Wave Gratings ◽  
Constraints Model

Response properties of MT neurons are often studied with “bikinetic” plaid stimuli, which consist of two superimposed sine wave gratings moving in different directions. Oculomotor studies using “unikinetic plaids” in which only one of the two superimposed gratings moves suggest that the eyes first move reflexively in the direction of the moving grating and only later converge on the perceived direction of the moving pattern. MT has been implicated as the source of visual signals that drives these responses. We wanted to know whether stationary gratings, which have little effect on MT cells when presented alone, would influence MT responses when paired with a moving grating. We recorded extracellularly from neurons in area MT and measured responses to stationary and moving gratings, and to their sums: bikinetic and unikinetic plaids. As expected, stationary gratings presented alone had a very modest influence on the activity of MT neurons. Responses to moving gratings and bikinetic plaids were similar to those previously reported and revealed cells selective for the motion of plaid patterns and of their components (pattern and component cells). When these neurons were probed with unikinetic plaids, pattern cells shifted their direction preferences in a way that revealed the influence of the static grating. Component cell preferences shifted little or not at all. These results support the notion that pattern-selective neurons in area MT integrate component motions that differ widely in speed, and that they do so in a way that is consistent with an intersection-of-constraints model. NEW & NOTEWORTHY Human perceptual and eye movement responses to moving gratings are influenced by adding a second, static grating to create a “unikinetic” plaid. Cells in MT do not respond to static gratings, but those gratings still influence the direction selectivity of some MT cells. The cells influenced by static gratings are those tuned for the motion of global patterns, but not those tuned only for the individual components of moving targets.

scholarly journals Constraints on the Source of Short-Term Motion Adaptation in Macaque Area MT. II. Tuning of Neural Circuit Mechanisms

2002 ◽  
Vol 88 (1) ◽  
pp. 370-382 ◽  
Author(s):  
Nicholas J. Priebe ◽  
Stephen G. Lisberger
Keyword(s):  
Time Course ◽  
Neural Circuit ◽  
Extrastriate Cortex ◽  
Target Velocity ◽  
Short Term ◽  
Motion Adaptation ◽  
Area Mt ◽  
Mt Neurons ◽  
Preferred Direction ◽  
Direction Tuning

Neurons in area MT, a motion-sensitive area of extrastriate cortex, respond to a step of target velocity with a transient-sustained firing pattern. The transition from a high initial firing rate to a lower sustained rate occurs over a time course of 20–80 ms and is considered a form of short-term adaptation. In the present paper, we compared the tuning of the adaptation to the neuron's tuning to direction and speed. The tuning of adaptation was measured with a condition/test paradigm in which a testing motion of the preferred direction and speed of the neuron under study was preceded by a conditioning motion: the direction and speed of the conditioning motion were varied systematically. The response to the test motion depended strongly on the direction of the conditioning motion. It was suppressed in almost all neurons by conditioning motion in the same direction and could be either suppressed or enhanced by conditioning motion in the opposite direction. Even in neurons that showed suppression for target motion in the nonpreferred direction, the adaptation and response direction tuning were the same. The speed tuning of adaptation was linked much less tightly to the speed tuning of the response of the neuron under study. For just more than 50% of neurons, the preferred speed of adaptation was more than 1 log unit different from the preferred response speed. Many neurons responded best when slow motions were followed by faster motions (acceleration) or vice versa (deceleration), suggesting that MT neurons may encode information about the change of target velocity over time. Finally, adaptation by conditioning motions of different directions, but not different speeds, altered the latency of the response to the test motion. The adaptation of latency recovered with shorter intervals between the conditioning and test motions than did the adaptation of response size, suggesting that latency and amplitude adaptation are mediated by separate mechanisms. Taken together with the companion paper, our data suggest that short-term motion adaptation in MT is a consequence of the neural circuit in MT and is not mediated by either input-specific mechanisms or intrinsic mechanisms related to the spiking of individual neurons. The circuit responsible for adaptation is tuned for both speed and direction and has the same direction tuning as the circuit responsible for the initial response of MT neurons.

Temporal Dynamics of Direction Tuning in Motion-Sensitive Macaque Area MT

2005 ◽  
Vol 93 (4) ◽  
pp. 2104-2116 ◽  
Author(s):  
János A. Perge ◽  
Bart G. Borghuis ◽  
Roger J. E. Bours ◽  
Martin J. M. Lankheet ◽  
Richard J. A. van Wezel
Keyword(s):  
Temporal Dynamics ◽  
Random Sequence ◽  
Nonlinear Effects ◽  
Direction Selectivity ◽  
Second Phase ◽  
Motion Direction ◽  
Area Mt ◽  
Mt Neurons ◽  
Static Nonlinearity ◽  
Preferred Direction

We studied the temporal dynamics of motion direction sensitivity in macaque area MT using a motion reverse correlation paradigm. Stimuli consisted of a random sequence of motion steps in eight different directions. Cross-correlating the stimulus with the resulting neural activity reveals the temporal dynamics of direction selectivity. The temporal dynamics of direction selectivity at the preferred speed showed two phases along the time axis: one phase corresponding to an increase in probability for the preferred direction at short latencies and a second phase corresponding to a decrease in probability for the preferred direction at longer latencies. The strength of this biphasic behavior varied between neurons from weak to very strong and was uniformly distributed. Strong biphasic behavior suggests optimal responses for motion steps in the antipreferred direction followed by a motion step in the preferred direction. Correlating spikes to combinations of motion directions corroborates this distinction. The optimal combination for weakly biphasic cells consists of successive steps in the preferred direction, whereas for strongly biphasic cells, it is a reversal of directions. Comparing reverse correlograms to combinations of stimuli to predictions based on correlograms for individual directions revealed several nonlinear effects. Correlations for successive presentations of preferred directions were smaller than predicted, which could be explained by a static nonlinearity (saturation). Correlations to pairs of (nearly) opposite directions were larger than predicted. These results show that MT neurons are generally more responsive when sudden changes in motion directions occur, irrespective of the preferred direction of the neurons. The latter nonlinearities cannot be explained by a simple static nonlinearity at the output of the neuron, but most likely reflect network interactions.

Spatial Summation, End Inhibition and Side Inhibition in the Middle Temporal Visual Area (MT)

2007 ◽  
Vol 97 (2) ◽  
pp. 1135-1148 ◽  
Author(s):  
Leo L. Lui ◽  
James A. Bourne ◽  
Marcello G. P. Rosa
Keyword(s):  
Spatial Summation ◽  
Distinct Group ◽  
Sine Wave ◽  
Wide Field ◽  
Area Mt ◽  
Temporal Area ◽  
Middle Temporal ◽  
Mt Neurons ◽  
Layer 4 ◽  
Stimulus Length

We investigated the responses of single neurons in the middle temporal area (MT) of anesthetized marmoset monkeys to sine-wave gratings of various lengths and widths. For the vast majority of MT cells maximal responses were obtained on presentation of gratings of specific dimensions, which were typically asymmetrical along the length and width axes. The strength of end inhibition was dependent on the width of the stimulus, with many cells showing clear end inhibition only when wide gratings were used. Conversely, the strength of side inhibition was dependent on stimulus length. Furthermore, for over one third of MT cells length summation properties could not be defined without consideration of stimulus width and vice versa. These neurons, which we refer to as “length–width inseparable” (LWI) cells, were rare in layer 4. The majority of LWI neurons was strongly inhibited by wide-field stimuli and responded preferentially to gratings that were elongated, along either the length or width dimensions. However, rather than forming a homogeneous and entirely distinct group, LWI cells represented the upper end of a continuum of complexity in spatial summation response properties, which characterized the population of MT cells. Only a minority of MT neurons (22.3%) showed no evidence of inhibition by wide-field stimuli, with this type of response being common among layer 5 cells. These results demonstrate distinct patterns of spatial selectivity in MT, supporting the notion that neurons in this area can perform various roles in terms of grouping and segmentation of motion signals.

Sign in / Sign up

Export Citation Format

Share Document