Effects Of Spatial Attention Research Articles

Attraction of Position Preference by Spatial Attention throughout Human Visual Cortex

Voluntary spatial attention concentrates neural resources at the attended location. Here, we examined the effects of spatial attention on spatial position selectivity in humans. We measured population receptive fields (pRFs) using high-field functional MRI (fMRI) (7T) while subjects performed an attention-demanding task at different locations. We show that spatial attention attracts pRF preferred positions across the entire visual field, not just at the attended location. This global change in pRF preferred positions systematically increases up the visual hierarchy. We model these pRF preferred position changes as an interaction between two components: an attention field and a pRF without the influence of attention. This computational model suggests that increasing effects of attention up the hierarchy result primarily from differences in pRF size and that the attention field is similar across the visual hierarchy. A similar attention field suggests that spatial attention transforms different neural response selectivities throughout the visual hierarchy in a similar manner.

Pupil size reflects the focus of feature-based attention.

We measured pupil size in adult human subjects while they selectively attended to one of two surfaces, bright and dark, defined by coherently moving dots. The two surfaces were presented at the same location; therefore, subjects could select the cued surface only on the basis of its features. With no luminance change in the stimulus, we find that pupil size was smaller when the bright surface was attended and larger when the dark surface was attended: an effect of feature-based (or surface-based) attention. With the same surfaces at nonoverlapping locations, we find a similar effect of spatial attention. The pupil size modulation cannot be accounted for by differences in eye position and by other variables known to affect pupil size such as task difficulty, accommodation, or the mere anticipation (imagery) of bright/dark stimuli. We conclude that pupil size reflects not just luminance or cognitive state, but the interaction between the two: it reflects which luminance level in the visual scene is relevant for the task at hand.

Correction: Spatial Attention Effects of Disgusted and Fearful Faces

Correction: Spatial Attention Effects of Disgusted and Fearful Faces

Stimulus competition modulates the joint effects of spatial and feature-based attention on visual sensitivity

Stimulus competition modulates the joint effects of spatial and feature-based attention on visual sensitivity

On the Role of Suppression in Spatial Attention: Evidence from Negative BOLD in Human Subcortical and Cortical Structures

There is clear evidence that spatial attention increases neural responses to attended stimuli in extrastriate visual areas and, to a lesser degree, in earlier visual areas. Other evidence shows that neurons representing unattended locations can also be suppressed. However, the extent to which enhancement and suppression is observed, their stimulus dependence, and the stages of the visual system at which they are expressed remains poorly understood. Using fMRI we set out to characterize both the task and stimulus dependence of neural responses in the lateral geniculate nucleus (LGN), primary visual cortex (V1), and visual motion area (V5) in humans to determine where suppressive and facilitatory effects of spatial attention are expressed. Subjects viewed a lateralized drifting grating stimulus, presented at multiple stimulus contrasts, and performed one of three tasks designed to alter the spatial location of their attention. In retinotopic representations of the stimulus location, we observed increasing attention-dependent facilitation and decreasing dependence on stimulus contrast moving up the visual hierarchy from the LGN to V5. However, in the representations of unattended locations of the LGN and V1, we observed suppression, which was not significantly dependent on the attended stimulus contrast. These suppressive effects were also found in the pulvinar, which has been frequently associated with attention. We provide evidence, therefore, for a spatially selective suppressive mechanism that acts at a subcortical level.

Feature-based attentional modulation of orientation perception in somatosensation.

In a reaction time study of human tactile orientation detection the effects of spatial attention and feature-based attention were investigated. Subjects had to give speeded responses to target orientations (parallel and orthogonal to the finger axis) in a random stream of oblique tactile distractor orientations presented to their index and ring fingers. Before each block of trials, subjects received a tactile cue at one finger. By manipulating the validity of this cue with respect to its location and orientation (feature), we provided an incentive to subjects to attend spatially to the cued location and only there to the cued orientation. Subjects showed quicker responses to parallel compared to orthogonal targets, pointing to an orientation anisotropy in sensory processing. Also, faster reaction times (RTs) were observed in location-matched trials, i.e., when targets appeared on the cued finger, representing a perceptual benefit of spatial attention. Most importantly, RTs were shorter to orientations matching the cue, both at the cued and at the uncued location, documenting a global enhancement of tactile sensation by feature-based attention. This is the first report of a perceptual benefit of feature-based attention outside the spatial focus of attention in somatosensory perception. The similarity to effects of feature-based attention in visual perception supports the notion of matching attentional mechanisms across sensory domains.

Spatial attention effects of disgusted and fearful faces.

Effective processing of threat-related stimuli is of significant evolutionary advantage. Given the intricate relationship between attention and the neural processing of threat-related emotions, this study manipulated attention allocation and emotional categories of threat-related stimuli as independent factors and investigated the time course of spatial-attention-modulated processing of disgusting and fearful stimuli. The participants were instructed to direct their attention either to the two vertical or to the two horizontal locations, where two faces and two houses would be presented. The task was to respond regarding the physical identity of the two stimuli at cued locations. Event-related potentials (ERP) evidences were found to support a two-stage model of attention-modulated processing of threat-related emotions. In the early processing stage, disgusted faces evoked larger P1 component at right occipital region despite the attention allocation while larger N170 component was elicited by fearful faces at right occipito-temporal region only when participants attended to houses. In the late processing stage, the amplitudes of the parietal P3 component enhanced for both disgusted and fearful facial expressions only when the attention was focused on faces. According to the results, we propose that the temporal dynamics of the emotion-by-attention interaction consist of two stages. The early stage is characterized by quick and specialized neural encoding of disgusting and fearful stimuli irrespective of voluntary attention allocation, indicating an automatic detection and perception of threat-related emotions. The late stage is represented by attention-gated separation between threat-related stimuli and neutral stimuli; the similar ERP pattern evoked by disgusted and fearful faces suggests a more generalized processing of threat-related emotions via top-down attentional modulation, based on which the defensive behavior in response to threat events is largely facilitated.

Generating a taxonomy of spatially cued attention for visual discrimination: effects of judgment precision and set size on attention.

Attention precues improve the performance of perceptual tasks in many but not all circumstances. These spatial attention effects may depend upon display set size or workload, and have been variously attributed to external noise filtering, stimulus enhancement, contrast gain, or response gain, or to uncertainty or other decision effects. In this study, we document systematically different effects of spatial attention in low- and high-precision judgments, with and without external noise, and in different set sizes in order to contribute to the development of a taxonomy of spatial attention. An elaborated perceptual template model (ePTM) provides an integrated account of a complex set of effects of spatial attention with just two attention factors: a set-size dependent exclusion or filtering of external noise and a narrowing of the perceptual template to focus on the signal stimulus. These results are related to the previous literature by classifying the judgment precision and presence of external noise masks in those experiments, suggesting a taxonomy of spatially cued attention in discrimination accuracy.

Response interference in touch, vision, and crossmodally: beyond the spatial dimension.

To date, tactile distractor processing has primarily been investigated by focusing on the spatial characteristics of distractors and the impact of their presentation on the orienting of attention. In two experiments, we examined the influence of tactile distractors when the location of stimulus presentation was kept constant, thus controlling for the effects of spatial attention. A response priming paradigm was used in which two stimuli were sequentially presented from the same (fixated) direction. Typically, target responses are facilitated when the previously presented distractor (i.e., the prime) happens to map on to the same response as compared to the distractor maps on to the opposite response. Similar response priming effects were observed for tactile and visual distractors within a unimodal experimental setting (Experiments 1a and 1b). Interestingly, however, when the targets and distractors were presented in different sensory modalities, only the visual distractors exerted a crossmodal effect on the subsequent processing of vibrotactile targets (Experiment 2). These results therefore indicate that visual stimuli automatically trigger their corresponding response even when the task at hand is not visual, whereas tactile stimuli are only processed up to the level of response generation when the participants' task is tactile.

Dissociating effects of movement preparation and spatial attention on visual processing: evidence from event-related potentials.

The present study investigated whether effects of movement preparation and visual spatial attention on visual processing can be dissociated. Movement preparation and visual spatial attention were manipulated orthogonally in a dual-task design. Ten participants covertly prepared unimanual lateral arm movements to one hemifield, while attending to visual stimuli presented either in the same or in the hemifield opposite to the movement goal. Event-related potentials to task-irrelevant visual stimuli were analysed. Both joint and distinct modulations of visual ERPs by visual spatial attention and movement preparation were observed: The latencies of all analysed peaks (P1, N1, P2) were shorter for matching (in terms of direction of attention and movement) versus non-matching sensory-motor conditions. The P1 amplitude, as well, depended on the sensory-motor matching: The P1 was larger for non-matching compared to matching conditions. By contrast, the N1 amplitude showed additive effects of sensory attention and movement preparation: with attention and movement preparation directed towards the visual stimulus the N1 was largest, with both directed opposite to the stimulus the N1 was smallest. P2 amplitudes, instead, were only modulated by sensory attention. The present data show that movement preparation and sensory spatial attention are tightly linked and interrelated, showing joint modulations throughout stimulus processing. At the same time, however, our data argue against the idea of identity of the two systems. Instead, sensory spatial attention and movement preparation seem to be processed at least partially independently, though still exerting a combined influence on visual stimulus processing.

Effects of attention on visible and invisible adapters.

It has been shown that attention can modulate the processing of a stimulus, even when it is invisible (Bahrami, Carmel, Walsh, Rees, & Lavie, 2008, Perception, 37, 1520-1528). Previous studies, however, investigated the effect of spatial attention on the processing of only invisible items. Thus, it remains unclear how the effect of spatial attention is distributed over visible and invisible items when these items are simultaneously attended at the same location. In the present study we addressed this question using two types of adapters, one visible and one invisible, and compared how attention affected the processing of each adapter. Moving gratings and tilted gratings were presented to each eye; the moving ones were dominant over the tilted ones. Both types of stimuli were located on the left and right sides of a fixation cross, and the participants performed a task that modulated their attention to one side or the other. In experiment 1 they were asked to detect the contrast decrement of one of the moving gratings, and in experiment 2 they detected a dot that was presented to both eyes. We found that attention increased the amount of motion aftereffects induced by the visible adapters. However, we did not find effects of attention on tilt aftereffects from the invisible adapters. Finally, in experiment 3 we found that attention successfully increased the amount of tilt aftereffects when the adapters were not suppressed. These findings suggest that spatial attention is more likely to influence visible items than invisible items in the same location. We also found that invisible items do not interfere with the attentional modulation of the processing of visible items.

How Attention Affects Spatial Resolution.

We summarize and discuss a series of psychophysical studies on the effects of spatial covert attention on spatial resolution, our ability to discriminate fine patterns. Heightened resolution is beneficial in most, but not all, visual tasks. We show how endogenous attention (voluntary, goal driven) and exogenous attention (involuntary, stimulus driven) affect performance on a variety of tasks mediated by spatial resolution, such as visual search, crowding, acuity, and texture segmentation. Exogenous attention is an automatic mechanism that increases resolution regardless of whether it helps or hinders performance. In contrast, endogenous attention flexibly adjusts resolution to optimize performance according to task demands. We illustrate how psychophysical studies can reveal the underlying mechanisms of these effects and allow us to draw linking hypotheses with known neurophysiological effects of attention.

A new perceptual paradigm to investigate the visual remapping of others’ tactile sensations onto one’s own body shows “mirror touch” for the hands

The last two decades have seen a multitude of publications showing the activation of an observer’s somatosensory cortical system during the observation of touch on another person. Behavioral demonstrations of “mirror touch,” however, have been slow in coming forward, and have so far primarily been shown as “visual remapping of touch” on the face. The present study uses a new paradigm to investigate the mirroring of others’ tactile sensations: a 2-AFC task of intensity judgment for touch on the observer’s left and right index finger pads. Observers viewed a left and right hand in an egocentric position, which were either touched passively (pencil moving to touch index finger pad) or actively sought touch (index finger moving to touch pencil). Touch and no-touch events for the two viewed hands were designed to eliminate confounding effects of spatial attention. Felt touches were either concurrent with viewed touch or no-touch events, or were delayed in time to assess potential response bias. The findings demonstrate visual remapping of touch for touch on the hands. If touch was shown on one of the hands only (e.g., left), observers were more likely to perceive touch on the same hand (i.e., their own left hand) as more intense than touch on the other hand even if tactile intensities did not differ, compared to touch shown on both or neither hand. These remapping effects occurred only when viewed and felt touches were concurrent, they were strongly modulated by the way in which viewed touch was incurred, and they were more reliable for touch on the left hand. A second, control experiment, in which touch observation was replaced by bright dots shown on or next to the finger pads, confirmed that these effects were largely due to genuine tactile mirroring rather than to somatotopic cueing. This 2-AFC tactile intensity judgment task may be a useful paradigm to investigate the remapping of others’ tactile sensations onto an observer’s own body.

Exogenous spatial attention: evidence for intact functioning in adults with autism spectrum disorder.

Deficits or atypicalities in attention have been reported in individuals with autism spectrum disorder (ASD), yet no consensus on the nature of these deficits has emerged. We conducted three experiments that paired a peripheral precue with a covert discrimination task, using protocols for which the effects of covert exogenous spatial attention on early vision have been well established in typically developing populations. Experiment 1 assessed changes in contrast sensitivity, using orientation discrimination of a contrast-defined grating; Experiment 2 evaluated the reduction of crowding in the visual periphery, using discrimination of a letter-like figure with flanking stimuli at variable distances; and Experiment 3 assessed improvements in visual search, using discrimination of the same letter-like figure with a variable number of distractor elements. In all three experiments, we found that exogenous attention modulated visual discriminability in a group of high-functioning adults with ASD and that it did so in the same way and to the same extent as in a matched control group. We found no evidence to support the hypothesis that deficits in exogenous spatial attention underlie the emergence of core ASD symptomatology.

36. Spatial attention mechanisms in migraine children with imploding or exploding pain: A topographical SEP study

Different pathophysiological mechanisms are supposed to work in migraineurs with either imploding or exploding pain. Previous studies demonstrated that spatial attention modulates somatosensory evoked potential (SEP) amplitudes as from 40 ms of latency. Our aim was to investigate the effect of spatial attention on the SEP amplitude and topography in migraine children with imploding or exploding pain. We studied 10 migraineurs with imploding pain and 9 migraine children with exploding pain. SEPs to median nerve stimulation were recorded from 31 scalp electrodes in a neutral condition (NC) and in a spatial attention condition (SAC), in which the subjects had to count tactile stimuli delivered on the stimulated hand. The P40 amplitude increase during SAC, as compared to NC, was higher in patients with exploding than with imploding pain. While in imploding migraineurs the N140 amplitude increase during SAC was prevalent in the centro-parietal region, it mainly involved the frontal region in exploding patients. Our results suggest that in pediatric migraine psychophysiological mechanisms subtending spatial attention depend on pain direction.

Effects of spatial attention on motion aftereffects.

Effects of spatial attention on motion aftereffects.

The effect of spatial attention on adaptation induced by visible and invisible stimuli

The effect of spatial attention on adaptation induced by visible and invisible stimuli

Novel Color Stimuli for Studying Spatial Attention

The effects of covert spatial attention on color processing are not well known. Although feature-based attention to color is known to improve discrimination performance, no studies (we know of) have examined the effects of spatial cueing on color processing. Here, we report results using a novel color stimulus that incorporates many of the desirable features found in visual motion stimuli commonly used in spatial attention tasks. The stimuli were circular patches (3.23° radius) comprised of ~660 squares, each with a color randomly drawn from a Gaussian distribution along one axis of DKL space, plus a randomly chosen luminance increment or decrement. Similar to dot-motion stimuli, each square was reborn after a fixed "lifetime" with a new color and luminance. By varying the mean and standard deviation of the Gaussian distribution, we defined stimuli that differed from one another in discriminability. We used these stimuli in a spatial attention task. In the main experiment, human subjects were shown 4 patches (1 in each quadrant at 8° eccentricity) while maintaining central fixation, and the mean color in one of the patches changed during the trial. The task was to report the "direction" of the color change (2AFC). In 50% of trials (cued block), a pre-stimulus cue indicated (100% valid) the location of the impending change; otherwise, the change could occur at any of the 4 patches (uncued block). In a control experiment, subjects performed the same 2AFC task with a single patch. Results from 3 subjects show that thresholds in the cued block were significantly lower than those in the uncued block, and nearly identical to those in the single-patch control. These results demonstrate that spatial cues can selectively enhance the processing of color stimuli, and illustrate the usefulness of these novel stimuli for studying spatial attention to color. Meeting abstract presented at VSS 2013

3D spatial attention effects are independent of projected 2D size and location for older and younger observers

3D spatial attention effects are independent of projected 2D size and location for older and younger observers

3D spatial attention effects are independent of projected 2D size and location for older and younger observers

Previous research has found the reaction time (RT) to light change targets when performing a car following task, is partially dependent on the distance in depth of the target from the driver. Researchers have concluded from this evidence that the spatial extent of attention is three dimensional (3D) during dual-task driving. However, in prior experiments the effect of two-dimensional (2D) projected size and position was not experimentally controlled. If spatial attention is 3D, then there should be an effect of target distance when 2D projected size and position are constant. The purpose of the current work was to assess this hypothesis. We manipulated the size and position of light-change targets at different depths to hold the projected size and position of targets constant between blocks. Although projected size and position were identical in this experiment, the results demonstrated that for younger and older drivers, targets further from the driver were responded to more slowly than targets closer to the driver. These results demonstrate that 3D attention effects are not dependent on projected size or position, and that the mechanism of 3D attention is present in younger and older drivers. These results, considered with the findings of other studies, suggest that tests to assess crash risk, such as the UFOV, are limited in scope because such tests fail to incorporate variation in attention as a function of distance.