Effects Of Spatial Attention Research Articles

Commentary: Top-down and bottom-up modulation of pain-induced oscillations.

Commentary: Top-down and bottom-up modulation of pain-induced oscillations.

Persistent perceptual grouping effects in the evaluation of simple arithmetic expressions.

Landy and Goldstone (2007a, 2010) demonstrated that an explicit rule, operator precedence for simple arithmetic expressions, is enforced in part by perceptual processes like unit formation and attention. When perceptual grouping competes with operator precedence, errors increase. We replicated this result (Exp. 1) and investigated whether perceptual grouping effects persist when the visual stimulus is presented briefly and then masked (Exp. 2) and when verbal recoding is encouraged through vocal expression (Exp. 3). We found that perceptual-grouping effects persisted in the masking condition, suggesting that the mental representations of arithmetic expressions retain visuospatial characteristics. Similarly, verbalization of the expressions did not eliminate perceptual-grouping effects, suggesting that participants were not verbally recoding. In sum, the persistent effects of unit formation and spatial attention emphasize the importance of perceptual processing in the development of human expertise in this domain.

ID 96 – Spatial attention effect on SEP components differentiates migraine children with imploding pain from those with exploding pain

Objectives Different pathophysiological mechanisms have been demonstrated in young migraineurs with either imploding (IP) or exploding (EP) pain (Iacovelli et al., 2013). Our aim was to investigate whether the effect of spatial attention on SEPs is different between IP and EP migraineurs. Methods We studied 10 IP migraineurs and 9 EP migraine children. SEPs to median nerve stimulation were recorded from 31 scalp electrodes in neutral condition (NC) and in spatial attention condition (SAC), in which subject had to count tactile stimuli delivered on the stimulated hand. Results In the frontal region the N140 amplitude increase in SAC was higher in EP than IP migraineurs ( F = 6.41, p = 0.01). In both NC ( F = 15, p F = 10.2, p = 0.001), the N140 latency was shorter in IP than in EP patients. In NC, the N120 latency was shorter in IP than in EP migraineurs ( F = 6.5, p = 0.01). In EP patients, but not in IP migraineurs, the P100 latency was shorter in SAC than in NC ( p = 0.04). Conclusions Our results suggest that the psychophysiological mechanisms underlying spatial attention are different in migraine children with imploding or exploding pain. Key message This study confirms that pain directionality represents an important phenotypic aspect of pediatric migraine.

Memory-based attentional capture by colour and shape contents in visual working memory

ABSTRACTCurrent theories assume that there is substantial overlap between visual working memory (VWM) and visual attention functioning, such that active representations in VWM automatically act as an attentional set, resulting in attentional biases towards objects that match the mnemonic content. Most evidence for this comes from visual search tasks in which a distractor similar to the memory interferes with the detection of a simultaneous target. Here we provide additional evidence using one of the most popular paradigms in the literature for demonstrating an active attentional set: The contingent spatial orienting paradigm of Folk and colleagues. This paradigm allows memory-based attentional biases to be more directly attributed to spatial orienting. Experiment 1 demonstrated a memory-contingent spatial attention effect for colour but not for shape contents of VWM. Experiment 2 tested the hypothesis that the placeholders used for spatial cueing interfered with the shape processing, and showed that memory-based attentional capture for shape returned when placeholders were removed. The results of the present study are consistent with earlier findings from distractor interference paradigms, and provide additional evidence that biases in spatial orienting contribute to memory-based influences on attention.

A Source for Feature-Based Attention in the Prefrontal Cortex

In cluttered scenes, we can use feature-based attention to quickly locate a target object. To understand how feature attention is used to find and select objects for action, we focused on the ventral prearcuate (VPA) region of prefrontal cortex. In a visual search task, VPA cells responded selectively to search cues, maintained their feature selectivity throughout the delay and subsequent saccades, and discriminated the search target in their receptive fields with a time course earlier than in FEF or IT cortex. Inactivation of VPA impaired the animals' ability to find targets, and simultaneous recordings in FEF revealed that the effects of feature attention were eliminated while leaving the effects of spatial attention in FEF intact. Altogether, the results suggest that VPA neurons compute the locations of objects with the features sought and send this information to FEF to guide eye movements to those relevant stimuli.

Stimulus competition mediates the joint effects of spatial and feature-based attention.

Distinct attentional mechanisms enhance the sensory processing of visual stimuli that appear at task-relevant locations and have task-relevant features. We used a combination of psychophysics and computational modeling to investigate how these two types of attention--spatial and feature based--interact to modulate sensitivity when combined in one task. Observers monitored overlapping groups of dots for a target change in color saturation, which they had to localize as being in the upper or lower visual hemifield. Pre-cues indicated the target's most likely location (left/right), color (red/green), or both location and color. We measured sensitivity (d') for every combination of the location cue and the color cue, each of which could be valid, neutral, or invalid. When three competing saturation changes occurred simultaneously with the target change, there was a clear interaction: The spatial cueing effect was strongest for the cued color, and the color cueing effect was strongest at the cued location. In a second experiment, only the target dot group changed saturation, such that stimulus competition was low. The resulting cueing effects were statistically independent and additive: The color cueing effect was equally strong at attended and unattended locations. We account for these data with a computational model in which spatial and feature-based attention independently modulate the gain of sensory responses, consistent with measurements of cortical activity. Multiple responses then compete via divisive normalization. Sufficient competition creates interactions between the two cueing effects, although the attentional systems are themselves independent. This model helps reconcile seemingly disparate behavioral and physiological findings.

Object-based spatial attention when objects have sufficient depth cues.

Attention directed to a part of an object tends to obligatorily spread over all of the spatial regions that belong to the object, which may be critical for rapid object-recognition in cluttered visual scenes. Previous studies have generally used simple rectangles as objects and have shown that attention spreading is reflected by amplitude modulation in the posterior N1 component (150-200 ms poststimulus) of event-related potentials, while other interpretations (i.e., rectangular holes) may arise implicitly in early visual processing stages. By using modified Kanizsa-type stimuli that provided less ambiguity of depth ordering, the present study examined early event-related potential spatial-attention effects for connected and separated objects, both of which were perceived in front of (Experiment 1) and in back of (Experiment 2) the surroundings. Typical P1 (100-140 ms) and N1 (150-220 ms) attention effects of ERP in response to unilateral probes were observed in both experiments. Importantly, the P1 attention effect was decreased for connected objects compared to separated objects only in Experiment 1, and the typical object-based modulations of N1 were not observed in either experiment. These results suggest that spatial attention spreads over a figural object at earlier stages of processing than previously indicated, in three-dimensional visual scenes with multiple depth cues.

Directional asymmetry in contrast sensitivity during smooth pursuit eye movement depends on spatial frequency

Abstract It is known that smooth pursuit eye movement (SPEM) modulates visual contrast sensitivity in an asymmetric manner. For instance, Schutz et al. (2007) reported that contrast sensitivity to a 1 c/deg grating is higher when it drifts in the same direction with the SPEM than in the opposite direction. They interpret this asymmetry in terms of the effect of spatial attention that moves together with, or even leads, the eye. The present study shows that this asymmetry is reversed at high spatial frequency bands. We measured contrast sensitivity for a spatially localized grating (Gabor patch) of 11 c/deg. The spatial window of the grating (s.d. of H0.8 x V0.4 deg) moved in the same velocity with SPEM (1.5 deg/sec), and thereby it was static on the retinal coordinate. The grating within spatial window drifted on the retina either in the same direction or in the opposite direction of SPEM. We found that for a range of retinal temporal frequencies tested (1.4-22.5 Hz), the observer's contrast sensitivity was substantially higher (0.1-0.25 log unit) when the grating drifted in the opposite direction of SPEM than in the same direction. This asymmetry was also observed for the cut-off temporal frequencies for a grating with a contrast of 0.5. For gratings of a low spatial frequency (0.5 c/deg), the cut off frequency was little, or not, higher for gratings in the same same direction than in the opposite direction of SPEM, consistent with the previous study. These results indicate that during smooth pursuit, the visual system becomes more sensitive to high-spatial frequency signals that moves slower than the eye than those that moves faster than the eye. The results cannot be well accounted for neither by spatial attention nor by sensitivity modulations of parvocellular and magnocellular channels. Meeting abstract presented at VSS 2015.

Modulation of intracranial field potential responses in the human large-scale attention network during a spatial attention task

Spatial attention is mediated through a large-scale network that includes occipital, temporal, parietal and frontal cortical regions. While the network architecture has been well characterized using neuroimaging methods, less is known about the temporal dynamics in local regions and across the network. Here, we explored the modulatory effects of spatial attention throughout this cortical network by analyzing intracranial field potentials recorded from 538 ECoG electrodes implanted in 6 epilepsy patients. We examined the effects of attention using a variant of the Eriksen flanker task, where subjects were cued by an exogenous stimulus to the spatial location of an upcoming target stimulus which, after a variable delay period, was presented embedded in a circular array of shapes. Subjects had to differentiate between barrel or bowtie target stimuli flanked either by congruent or incongruent shapes. Using our probabilistic atlas of the human visual system, we localized the recorded ECoG signals to topographically organized brain areas and linked them to functional brain imaging data from normal subjects. We found spatially constrained visual response fields in 175 electrodes, as indicated by differential cue-related activity, obtained from both induced broadband power and evoked potentials. We examined response modulation from those electrodes during the delay period of the task when subjects either attended to or away from the response field. Further, we related these results to changes in the BOLD signal measured in normal subjects performing the same task. We found that covert spatial attention affected evoked event-related potentials and induced low frequency (4-20Hz) and broadband high gamma (50-200Hz) power differentially along the dorsal pathway through nodes of the fronto-parietal attention network, from V1 through intraparietal sulcus areas IPS0-IPS5 and the frontal eye fields. Meeting abstract presented at VSS 2015

Frequency tagging of steady-state evoked potentials to explore the crossmodal links in spatial attention between vision and touch.

The sustained periodic modulation of a stimulus induces an entrainment of cortical neurons responding to the stimulus, appearing as a steady-state evoked potential (SS-EP) in the EEG frequency spectrum. Here, we used frequency tagging of SS-EPs to study the crossmodal links in spatial attention between touch and vision. We hypothesized that a visual stimulus approaching the left or right hand orients spatial attention toward the approached hand, and thereby enhances the processing of vibrotactile input originating from that hand. Twenty-five subjects took part in the experiment: 16-s trains of vibrotactile stimuli (4.2 and 7.2 Hz) were applied simultaneously to the left and right hand, concomitantly with a punctate visual stimulus blinking at 9.8 Hz. The visual stimulus was approached toward the left or right hand. The hands were either uncrossed (left and right hands to the left and right of the participant) or crossed (left and right hands to the right and left of the participant). The vibrotactile stimuli elicited two distinct SS-EPs with scalp topographies compatible with activity in the contralateral primary somatosensory cortex. The visual stimulus elicited a third SS-EP with a topography compatible with activity in visual areas. When the visual stimulus was over one of the hands, the amplitude of the vibrotactile SS-EP elicited by stimulation of that hand was enhanced, regardless of whether the hands were uncrossed or crossed. This demonstrates a crossmodal effect of spatial attention between vision and touch, integrating proprioceptive and/or visual information to map the position of the limbs in external space.

Independent effects of eye gaze and spatial attention on the processing of tactile events: Evidence from event-related potentials

Directing one’s gaze at a body part reduces detection speed and enhances the processing of tactile stimuli presented at the gazed location. Given the close links between spatial attention and the oculomotor system it is possible that these gaze- dependent modulations of touch are mediated by attentional mechanisms. To investigate this possibility, gaze direction and sustained tactile attention were orthogonally manipulated in the present study. Participants covertly attended to one hand to perform a tactile target-nontarget discrimination while they gazed at the same or opposite hand. Spatial attention resulted in enhancements of the somatosensory P100 and Nd components. In contrast, gaze resulted in modulations of the N140 component with more positive ERPs for gazed than non gazed stimuli. This dissociation in the pattern and timing of the effects of gaze and attention on somatosensory processing reveals that gaze and attention have independent effects on touch.

Effects of spatial cues on color-change detection in humans.

Studies of covert spatial attention have largely used motion, orientation, and contrast stimuli as these features are fundamental components of vision. The feature dimension of color is also fundamental to visual perception, particularly for catarrhine primates, and yet very little is known about the effects of spatial attention on color perception. Here we present results using novel dynamic color stimuli in both discrimination and color-change detection tasks. We find that our stimuli yield comparable discrimination thresholds to those obtained with static stimuli. Further, we find that an informative spatial cue improves performance and speeds response time in a color-change detection task compared with an uncued condition, similar to what has been demonstrated for motion, orientation, and contrast stimuli. Our results demonstrate the use of dynamic color stimuli for an established psychophysical task and show that color stimuli are well suited to the study of spatial attention.

Exposing the cuing task: the case of gaze and arrow cues.

The prevailing theoretical accounts of social cognitive processes propose that attention is preferentially engaged by social information. However, empirical investigations report virtually indistinguishable attention effects for social (e.g., gaze) and nonsocial (e.g., arrow) stimuli when a cuing task is used. Here, we show that this discrepancy between theory and data reflects a difference in how the extraneous processes induced by the cuing task's parameters (i.e., tonic alertness and voluntary temporal preparation) modulate cue-specific attentional effects. Overall, we found that tonic alertness and voluntary temporal preparation interacted within the cuing task, resulting in underadditive magnitudes of spatial orienting and superadditive magnitudes of the foreperiod effect. However, those interactions differentially affected social and nonsocial attention. While typical rapid social orienting was resilient to changing task parameters, sustained social orienting was eliminated only when the contribution of both extraneous processes was reduced. In contrast, orienting elicited by nonsocial arrows grew in magnitude with the reduction of voluntary temporal preparation and was delayed by the joint reduction of tonic alertness and voluntary temporal preparation. Together, these data indicate that cue-specific attention effects are masked by task dynamics of the cuing paradigm and highlight a pivotal role of the cuing task parameters in both the measurement and the theoretical attribution of spatial attention effects.

Attention and normalization circuits in macaque V1.

Attention affects neuronal processing and improves behavioural performance. In extrastriate visual cortex these effects have been explained by normalization models, which assume that attention influences the circuit that mediates surround suppression. While normalization models have been able to explain attentional effects, their validity has rarely been tested against alternative models. Here we investigate how attention and surround/mask stimuli affect neuronal firing rates and orientation tuning in macaque V1. Surround/mask stimuli provide an estimate to what extent V1 neurons are affected by normalization, which was compared against effects of spatial top down attention. For some attention/surround effect comparisons, the strength of attentional modulation was correlated with the strength of surround modulation, suggesting that attention and surround/mask stimulation (i.e. normalization) might use a common mechanism. To explore this in detail, we fitted multiplicative and additive models of attention to our data. In one class of models, attention contributed to normalization mechanisms, whereas in a different class of models it did not. Model selection based on Akaike's and on Bayesian information criteria demonstrated that in most cells the effects of attention were best described by models where attention did not contribute to normalization mechanisms. This demonstrates that attentional influences on neuronal responses in primary visual cortex often bypass normalization mechanisms.

Somatosensory spatial attention modulates amplitudes, latencies, and latency jitter of laser-evoked brain potentials.

Several studies provided evidence that the amplitudes of laser-evoked potentials (LEPs) are modulated by attention. However, previous reports were based on across-trial averaging of LEP responses at the expense of losing information about intertrial variability related to attentional modulation. The aim of this study was to investigate the effects of somatosensory spatial attention on single-trial parameters (i.e., amplitudes, latencies, and latency jitter) of LEP components (N2 and P2). Twelve subjects participated in a sustained spatial attention paradigm while noxious laser stimuli (left hand) and noxious electrical stimuli (right hand) were sequentially delivered to the dorsum of the respective hand with nonnoxious air puffs randomly interspersed within the sequence of noxious stimuli. Participants were instructed to mentally count all stimuli (i.e., noxious and nonnoxious) applied to the attended location. Laser stimuli, presented to the attended hand (ALS), elicited larger single-trial amplitudes of the N2 component compared with unattended laser stimuli (ULS). In contrast, single-trial amplitudes of the P2 component were not significantly affected by spatial attention. Single-trial latencies of the N2 and P2 were significantly smaller for ALS vs. ULS. Additionally, the across-trial latency jitter of the N2 component was reduced for ALS. Conversely, the latency jitter of the P2 component was smaller for ULS compared with ALS. With the use of single-trial analysis, the study provided new insights into brain dynamics of LEPs related to spatial attention. Our results indicate that single-trial parameters of LEP components are differentially modulated by spatial attention.

Hemisphere-dependent attentional modulation of human parietal visual field representations.

Posterior parietal cortex contains several areas defined by topographically organized maps of the contralateral visual field. However, recent studies suggest that ipsilateral stimuli can elicit larger responses in the right than left hemisphere within these areas, depending on task demands. Here we determined the effects of spatial attention on the set of visual field locations (the population receptive field [pRF]) that evoked a response for each voxel in human topographic parietal cortex. A two-dimensional Gaussian was used to model the pRF in each voxel, and we measured the effects of attention on not only the center (preferred visual field location) but also the size (visual field extent) of the pRF. In both hemispheres, larger pRFs were associated with attending to the mapping stimulus compared with attending to a central fixation point. In the left hemisphere, attending to the stimulus also resulted in more peripheral preferred locations of contralateral representations, compared with attending fixation. These effects of attention on both pRF size and preferred location preserved contralateral representations in the left hemisphere. In contrast, attentional modulation of pRF size but not preferred location significantly increased representation of the ipsilateral (right) visual hemifield in right parietal cortex. Thus, attention effects in topographic parietal cortex exhibit hemispheric asymmetries similar to those seen in hemispatial neglect. Our findings suggest potential mechanisms underlying the behavioral deficits associated with this disorder.

Independent effects of bottom-up temporal expectancy and top-down spatial attention. An audiovisual study using rhythmic cueing.

Selective attention to a spatial location has shown enhanced perception and facilitate behavior for events at attended locations. However, selection relies not only on where but also when an event occurs. Recently, interest has turned to how intrinsic neural oscillations in the brain entrain to rhythms in our environment, and, stimuli appearing in or out of sync with a rhythm have shown to modulate perception and performance. Temporal expectations created by rhythms and spatial attention are two processes which have independently shown to affect stimulus processing but it remains largely unknown how, and if, they interact. In four separate tasks, this study investigated the effects of voluntary spatial attention and bottom-up temporal expectations created by rhythms in both unimodal and crossmodal conditions. In each task the participant used an informative cue, either color or pitch, to direct their covert spatial attention to the left or right, and respond as quickly as possible to a target. The lateralized target (visual or auditory) was then presented at the attended or unattended side. Importantly, although not task relevant, the cue was a rhythm of either flashes or beeps. The target was presented in or out of sync (early or late) with the rhythmic cue. Results showed participants were faster responding to spatially attended compared to unattended targets in all tasks. Moreover, there was an effect of rhythmic cueing upon response times in both unimodal and crossmodal conditions. Responses were faster to targets presented in sync with the rhythm compared to when they appeared too early in both crossmodal tasks. That is, rhythmic stimuli in one modality influenced the temporal expectancy in the other modality, suggesting temporal expectancies created by rhythms are crossmodal. Interestingly, there was no interaction between top-down spatial attention and rhythmic cueing in any task suggesting these two processes largely influenced behavior independently.

Attending to the Unseen: The Effects of Spatial Attention on Neural Responses to Visible and Invisible Stimuli

Mechanisms of selective attention are important for prioritising behaviourally relevant sensory inputs. In vision, attention can be deployed to bring barely perceptible stimuli into conscious awareness, supporting the common view that attention and awareness are intimately related. Recently, however, evidence has suggested that attention and awareness might be based on distinct and dissociable neural mechanisms. This thesis investigated whether the voluntary allocation of attention to a cued region of space can modulate neural representations of visual stimuli that are subjectively invisible. Participants (N = 23) attended covertly to one of two flickering image streams on either side of fixation, and reported which of two consecutive intervals contained a target embedded in dynamic noise. Coherence of the signal was manipulated to be highly visible, moderately visible, or invisible. Scalp-recorded electroencephalography (EEG) was used to measure neural responses to the flickering signal and noise stimuli. Fourier analyses of these recordings revealed activity peaks over contralateral occipital electrodes at the unique frequencies of signal and noise stimulation. Attentional enhancement of neural responses to noise stimuli indicated that the manipulation of attention was successful. Additionally, behavioural data confirmed that the manipulation of signal awareness was successful. As predicted, spatial attention modulated neural responses to visible targets, which were enhanced briefly after target onset and suppressed toward the end of the interval. Also as predicted, spatial attention modulated neural responses to invisible targets, supporting theories that attention can dissociate from awareness. The nature of this modulation was qualitatively different to that of visible targets, however, with no early enhancement but a late suppression with attention. Reasons for this unexpected pattern of results are discussed, including the possibility that spatial attention interacted with another neural process late in the trial interval.

Emergence of visual objects involves multiple stages of spatial selection.

Attention may select objects or perceptual groups as fundamental units. Previous studies with event-related potentials (ERPs) have found that obligatory attention-spreading over spatial regions within stable objects is associated with intermediate feedforward visual processing, as reflected by the posterior N1 component of the ERP at a latency of 140-180ms. The present study examined object-based spatial attention effects in response to individual objects, by recording lateralized ERP attention effects over the posterior scalp (i.e., contralateral versus ipsilateral to the attended visual fields). The stumuli were bilateral unfilled line objects with minimal figural enhancement, and their connectedness and the difficulty of the perceptual task were manipulated. The effects of spatial attention on successive ERP components (N1, P2, and N2) provided information on the timing of the different stages of processing that underlie the formation of perceptual objects.

Modulatory effects of movement sequence preparation and covert spatial attention on early somatosensory input to non-primary motor areas.

Early frontal somatosensory evoked potentials (SEPs) (i.e., N30) are known to be modulated by movement. Furthermore, individuals with prefrontal lesions have enhanced early frontal SEPs. However, it is currently unclear through what mechanism the prefrontal cortex may modulate early frontal SEPs. The current study investigated whether prefrontal modulatory effects on frontal SEPs may depend on the relevancy of somatosensory input for movement (i.e., interaction with motor areas). Two experiments were conducted to determine whether selective spatial attention alone (Experiment 1-Attend and Mentally Count) or when using attended somatosensory input in the preparation of finger sequences with the limb contralateral to somatosensory stimulation (Experiment 2-Attend for Movement Preparation) could modulate SEPs. In Experiment 1, SEPs elicited by median nerve (MN) stimulation at both wrists were measured in trials when individuals attended and mentally counted vibrotactile (VibT) input at either index finger. In Experiment 2, SEPs elicited by MN stimulation at the left wrist were measured in trials when individuals used attended VibT input at the left index finger to prepare finger sequences that were contralateral to MN stimulation. In both experiments, control conditions were performed where participants received passive VibT and MN stimulation. Results from Experiment 1 confirmed that selective spatial attention alone does not modulate frontal N30 peak amplitudes. However, Experiment 2 revealed that frontal N30 peak amplitudes were decreased (i.e., gated) when individuals used attended VibT input at the left index finger to prepare contralateral finger sequences. These results support a role of sensory gating of early frontal SEPs during finger sequence preparation of the limb contralateral to MN stimulation that may result from increased activity in prefrontal, motor preparatory areas, and basal ganglia.