Crossmodal Links In Spatial Attention Research Articles

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.

Visual unimodal grouping mediates auditory attentional bias in visuo-spatial working memory

Audiovisual links in spatial attention have been reported in many previous studies. However, the effectiveness of auditory spatial cues in biasing the information encoding into visuo-spatial working memory (VSWM) is still relatively unknown. In this study, we addressed this issue by combining a cuing paradigm with a change detection task in VSWM. Moreover, we manipulated the perceptual organization of the to-be-remembered visual stimuli. We hypothesized that the auditory effect on VSWM would depend on the perceptual association between the auditory cue and the visual probe. Results showed, for the first time, a significant auditory attentional bias in VSWM. However, the effect was observed only when the to-be-remembered visual stimuli were organized in two distinctive visual objects. We propose that these results shed new light on audio-visual crossmodal links in spatial attention suggesting that, apart from the spatio-temporal contingency, the likelihood of perceptual association between the auditory cue and the visual target can have a large impact on crossmodal attentional biases.

Neuromodulation of crossmodal influences on visual cortex excitability

Crossmodal interactions occur not only within brain regions deemed to be heteromodal, but also within primary sensory areas, traditionally considered as modality-specific. So far, mechanisms of crossmodal interactions in primary visual areas remain largely unknown. In the present study, we explored the effect of crossmodal stimuli on phosphene perception, induced by single-pulse transcranial magnetic stimulation (sTMS) delivered to the occipital visual cortex. In three experiments, we showed that redundant auditory and/or tactile information facilitated the detection of phosphenes induced by occipital sTMS, applied at sub-threshold intensity, which also increased their level of brightness, with the maximal enhancement occurring for trimodal stimulus combinations. Such crossmodal enhancement can be further boosted by the brain polarization of heteromodal areas mediating crossmodal links in spatial attention. Specifically, anodal transcranial direct current stimulation (tDCS) of both the occipital and the parietal cortices facilitated phosphene detection under unimodal conditions, whereas anodal tDCS of the parietal and temporal cortices enhanced phosphene detection selectively under crossmodal conditions, when auditory or tactile stimuli were combined with occipital sTMS. Overall, crossmodal interactions can enhance neural excitability within low-level visual areas, and tDCS can be used for boosting such crossmodal influences on visual responses, likely affecting mechanisms of crossmodal spatial attention involving feedback modulation from heteromodal areas on sensory-specific cortices. TDCS can effectively facilitate the integration of multisensory signals originating from the external world, hence improving visual perception.

Spatial attention affects the processing of tactile and visual stimuli presented at the tip of a tool: an event-related potential study

An event-related potential (ERP) experiment was conducted in order to investigate the nature of any cross-modal links in spatial attention during tool use. Tactile stimuli were delivered from the tip of two sticks, held in either a crossed or an uncrossed tools posture, while visual stimuli were presented along the length of each tool. Participants had to detect tactile deviant stimuli at the end of one stick while trying to ignore all other stimuli. Reliable ERP spatial attention effects to tactile stimuli were observed at early (160-180 ms) and later time epochs (>350 ms) when the tools were uncrossed. Reliable ERP attention effects to visual stimuli presented close to the tip of the tool and close to the hand were also observed in the uncrossed tools condition (time epoch 140-180 ms). These results are consistent with the claim that tool-use results in a shift of visuospatial attention toward the tip of the tool and also to attention being focused by the hand where the touch is felt.

Guiding Visual Attention by Exploiting Crossmodal Spatial Links: An Application in Air Traffic Control

Recent research on multimodal information processing has provided evidence for the existence of crossmodal links in spatial attention between vision, audition, and touch. The present study examined whether these links can be exploited to support attention allocation in workplaces that involve competing task demands and the potential for visual data overload. In particular, the effectiveness of tactile cues for guiding visual attention to the location of a critical event was tested in the context of an air traffic control simulation. Participants monitored a display depicting the flight paths of 40 aircraft and were presented with tactile cues indicating either just the occurrence, or both the occurrence and display location, of an event requiring a participant response. Tactile cuing, especially when combined with location information, resulted in significantly higher detection rates and faster response times to these events. These findings indicate that tactile cuing is a promising means of directing visual attention in a data-driven manner.

Spatial tuning of tactile attention modulates visual processing within hemifields: an ERP investigation of crossmodal attention

Recent event-related brain potential (ERP) studies have revealed crossmodal links in spatial attention, but have not yet investigated differences in the spatial tuning of attention between task-relevant and irrelevant modalities. We studied the spatial distribution of attention in vision under conditions where participants were instructed to attend to the left or right-hand in order to detect infrequent targets, and to entirely ignore visual stimuli presented via LEDs at two eccentricities in the left or right hemifield. Hands were located close to two of these four LEDs in different blocks. Visual N1 amplitudes were enhanced when visual stimuli in the cued hemifield were close to the attended hand, relative to visual stimuli presented at the other location on the same side. These within-hemifield attentional modulations of visual processing demonstrate that crossmodal attention is not distributed diffusely across an entire hemifield. The spatial tuning of tactile attention transfers crossmodally to affect vision, consistent with spatial selection at a multimodal level of representation.

On audiovisual spatial synergy: The fragility of the phenomenon

Recent literature has highlighted the importance and ubiquity of cross-modal links in spatial attention, whereby shifts in attention in one modality often induce corresponding shifts in other modalities. We attempted to provide further evidence for the case of audiovisual links during sustained endogenous attention by addressing several potential methodological confounds in previous demonstrations. However, we failed repeatedly to reproduce the phenomenon of spatial synergies between auditory and visual attention, found by Driver and Spence (1994) and frequently cited to support the automatic nature of cross-modal attention links. We discuss the results in light of recent evidence about cross-modal spatial links during sustained attention and support the idea that such links can weaken or even disappear under certain circumstances, such as during periods of sustained attention. The implication is that individuals can select inputs from different modalities from different locations more easily than previously had been thought.

Speech shadowing while driving: on the difficulty of splitting attention between eye and ear.

We investigated the role of cross-modal links in spatial attention in modulating the efficiency of dual-task performance. The difficulty of combining speech shadowing with a simulated driving task was modulated by the spatial location from which the speech was presented. In both single- and dual-task conditions, participants found it significantly easier to shadow one of two auditory streams when the relevant speech was presented from directly in front of them, rather than from the side. This frontal speech advantage was more pronounced when participants performed the demanding simulated driving task at the same time as shadowing than when they performed the shadowing task alone. These results demonstrate that people process auditory information more efficiently (with a lower overall dual-task decrement) when relevant auditory and visual stimuli are presented from the same, rather than different, spatial locations. These results are related to recent findings showing that there are extensive cross-modal links in spatial attention, and have clear implications for the design of better user interfaces.

Temporal dynamics of lateralized ERP components elicited during endogenous attentional shifts to relevant tactile events.

To investigate the temporal dynamics of lateralized event-related brain potential (ERP) components elicited during covert shifts of spatial attention, ERPs were recorded in a task where central visual symbolic cues instructed participants to direct attention to their left or right hand in order to detect infrequent tactile targets presented to that hand, and to ignore tactile stimuli presented to the other hand, as well as all randomly intermingled peripheral visual stimuli. In different blocks, the stimulus onset asynchrony (SOA) between cue and target was 300 ms, 700 ms, or 1,100 ms. Anterior and posterior ERP modulations sensitive to the direction of an attentional shift were time-locked to the attentional cue, rather than to the anticipated arrival of a task-relevant stimulus. These components thus appear to reflect central attentional control rather than the anticipatory preparation of sensory areas. In addition, attentional modulations of ERPs to task-irrelevant visual stimuli were found, providing further evidence for crossmodal links in spatial attention between touch and vision.

Shifts of attention in light and in darkness: an ERP study of supramodal attentional control and crossmodal links in spatial attention

Crossmodal links in spatial attention, uncovered by recent behavioural and electrophysiological studies, have been interpreted as evidence for supramodal processes controlling shifts of attention. However, previous experiments have usually been conducted in illuminated environments. Continuously available visuo-spatial information might result in shifts of attention being primarily guided by visible information, even when another modality is task-relevant. The present ERP study evaluated this. A symbolic auditory cue directed attention to the left or right hand. Participants had to detect infrequent tactile targets delivered to the cued hand, while ignoring any visual stimuli. Stimuli were presented either in a lit environment or in darkness. Although continuous ambient visuo-spatial information was eliminated in the latter condition, processing of task-irrelevant visual events was still modulated by spatial attention for the tactile task. Moreover, ERP correlates of attentional shifts in the cue–target interval were similar for both illumination conditions. This was further confirmed in a follow-up experiment where the darkness condition was repeated without any peripheral visual stimulation ever occurring. These findings demonstrate that the ERP correlates of crossmodal attention (both preparatory effects in the cue–target interval, and also modulations of stimulus-evoked components) do not depend on selection being guided by ambient visible information in a lit environment. They suggest instead that spatial shifts of attention are controlled supramodally.

Multisensory attention and tactile information-processing

Although a great deal is now known about the peripheral sensory mechanisms involved in tactile information processing [Ann Rev Psychol 1990;50:305], it is only more recently that we have started to gain a clearer understanding of the effects of selective attention on tactile perception [Front Biosci 2000;5:D894]. To date, the majority of this selective attention research has considered each modality in isolation. However, in order to deal with the multimodal selection problems of everyday life, we need to be able to coordinate our selective attention cross-modally [Philos Trans R Soc, Sec B 1998:353; Curr Biol 2000;10:R731]. In this review, I will highlight the results of behavioral studies demonstrating the existence of extensive cross-modal links in selective attention between touch, vision, audition, and even olfaction. In particular, the review is structured around two key research questions: First, “Can attention can be selectively directed to a particular sensory modality?”, and second “Are there cross-modal links in spatial attention?”. The results of recent neuroimaging studies that have started to elucidate some of the neural mechanisms underlying these cross-modal attentional effects are also discussed, and potential questions for future research outlined.

Crossmodal links in spatial attention are mediated by supramodal control processes: Evidence from event‐related potentials

Crossmodal links in spatial attention were studied in an experiment where participants had to detect peripheral tactile or visual targets on the attended side, while ignoring all stimuli on the unattended side and in the currently irrelevant modality. Both relevant locations and relevant modalities were specified on a trial‐by‐trial basis by auditory precues. Spatial orienting in the cue–target interval was reflected in anterior negativities and occipital positivities contralateral to the cued side, either when vision or touch was cued as relevant. These effects resembled previously reported ERP modulations during shifts of visual attention, implicating supramodal mechanisms in the control of spatial attention and demonstrating their independence of cue modality. Early effects of spatial attention on somatosensory and visual ERPs were of equivalent size for currently relevant and irrelevant modalities. Results support the idea that crossmodal links in spatial attention are mediated by supramodal control mechanisms.

Crossmodal links in spatial attention are mediated by supramodal control processes: Evidence from event-related potentials

Crossmodal links in spatial attention are mediated by supramodal control processes: Evidence from event-related potentials

Crossmodal links in endogenous and exogenous spatial attention: evidence from event-related brain potential studies

The adaptive control of behaviour in response to relevant external objects and events often requires the selection of information delivered by different sensory systems, but from the same region in external space. This can be facilitated by crossmodal links in the attentional processing of information across sensory modalities. Results from recent event-related potential (ERP) studies are reviewed that investigated mechanisms underlying such crossmodal links in spatial attention between vision, audition and touch. Crossmodal attention effects were observed for early modality-specific visual, auditory, and somatosensory ERP components, indicating that crossmodal links in spatial attention affect sensory-perceptual processes within modality-specific cortical regions. ERP modulations prior to target events but sensitive to the direction of an attentional shift were remarkably similar during anticipatory covert shifts of visual, auditory, or tactile attention. These results suggest that such attentional shifts are mediated by supramodal frontoparietal control mechanisms. Finally, ERP evidence is reviewed suggesting that effects of crossmodal links in endogenous (voluntary) as well as exogenous (involuntary) spatial attention are mediated by a representations of external space which are updated across postural changes.

Book Reviews

Book ReviewsBook ReviewsFred W. Mast and Pascal WallischFred W. MastSearch for more papers by this author and Pascal WallischSearch for more papers by this authorPublished OnlineNovember 17, 2006https://doi.org/10.1024//1421-0185.60.2.109bView Full Text ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinkedInReddit SectionsMoreFiguresReferencesRelatedDetails Volume 60Issue 2June 2001ISSN: 1421-0185eISSN: 1662-0879 tabs.informationSwiss Journal of Psychology (2001), 60, pp. 109-110 https://doi.org/10.1024//1421-0185.60.2.109b.© 2001Verlag Hans Huber

Tactile-visual links in exogenous spatial attention under different postures: convergent evidence from psychophysics and ERPs.

Tactile-visual links in spatial attention were examined by presenting spatially nonpredictive tactile cues to the left or right hand, shortly prior to visual targets in the left or right hemifield. To examine the spatial coordinates of any crossmodal links, different postures were examined. The hands were either uncrossed, or crossed so that the left hand lay in the right visual field and vice versa. Visual judgments were better on the side where the stimulated hand lay, though this effect was somewhat smaller with longer intervals between cue and target, and with crossed hands. Event-related brain potentials (ERPs) showed a similar pattern. Larger amplitude occipital N1 components were obtained for visual events on the same side as the preceding tactile cue, at ipsilateral electrode sites. Negativities in the Nd2 interval at midline and lateral central sites, and in the Nd1 interval at electrode Pz, were also enhanced for the cued side. As in the psychophysical results, ERP cueing effects during the crossed posture were determined by the side of space in which the stimulated hand lay, not by the anatomical side of the initial hemispheric projection for the tactile cue. These results demonstrate that crossmodal links in spatial attention can influence sensory brain responses as early as the N1, and that these links operate in a spatial frame-of-reference that can remap between the modalities across changes in posture.

Crossmodal links in spatial attention between vision, audition, and touch: evidence from event-related brain potentials

Results from event-related potential (ERP) studies are reviewed that investigated crossmodal links in spatial attention between vision, audition and touch to find out which stages in the processing of sensory stimuli are affected by such crossmodal links. ERPs were recorded in response to visual, auditory, and tactile stimuli under conditions where attention was directed to a specific location within one (primary) modality, while stimuli in another (secondary) modality were to be ignored regardless of their position. Systematic ERP effects of spatial attention were observed not only in the primary modality, but also for secondary modality stimuli, thus revealing crossmodal links in spatial attention. These links affected relatively early sensory-specific ERP components between 100 and 200 ms post-stimulus. Beyond 200 ms, ERPs to secondary modality stimuli were little affected by the current focus of attention within another modality. This pattern of results suggests that crossmodal links in spatial attention may affect sensory-perceptual processes within modality-specific cortical regions, but have little impact on later post-perceptual processing stages.

An event-related brain potential study of cross-modal links in spatial attention between vision and touch

Event-related potential (ERP) evidence for the existence of cross-modal links in endogenous spatial attention between vision and touch was obtained in an experiment where participants had to detect tactile or visual targets on the attended side and to ignore the irrelevant modality and stimuli on the unattended side. For visual ERPs, attentional modulations of occipital P1 and N1 components were present when attention was directed both within vision and within touch, indicating that links in spatial attention from touch to vision can affect early stages of visual processing. For somatosensory ERPs, attentional negativities starting around 140 ms poststimulus were present at midline and lateral central electrodes when touch was relevant. No attentional somatosensory ERP modulations were present when vision was relevant and tactile stimuli could be entirely ignored. However, in another task condition where responses were also required to infrequent tactile targets regardless of their location, visual-spatial attention modulated somatosensory ERPs. Unlike vision, touch apparently can be decoupled from attentional orienting within another modality unless it is potentially relevant.

Cross-modal selective attention: on the difficulty of ignoring sounds at the locus of visual attention.

In three experiments, we investigated whether the ease with which distracting sounds can be ignored depends on their distance from fixation and from attended visual events. In the first experiment, participants shadowed an auditory stream of words presented behind their heads, while simultaneously fixating visual lip-read information consistent with the relevant auditory stream, or meaningless "chewing" lip movements. An irrelevant auditory stream of words, which participants had to ignore, was presented either from the same side as the fixated visual stream or from the opposite side. Selective shadowing was less accurate in the former condition, implying that distracting sounds are harder to ignore when fixated. Furthermore, the impairment when fixating toward distractor sounds was greater when speaking lips were fixated than when chewing lips were fixated, suggesting that people find it particularly difficult to ignore sounds at locations that are actively attended for visual lipreading rather than merely passively fixated. Experiments 2 and 3 tested whether these results are specific to cross-modal links in speech perception by replacing the visual lip movements with a rapidly changing stream of meaningless visual shapes. The auditory task was again shadowing, but the active visual task was now monitoring for a specific visual shape at one location. A decrement in shadowing was again observed when participants passively fixated toward the irrelevant auditory stream. This decrement was larger when participants performed a difficult active visual task there versus fixating, but not for a less demanding visual task versus fixation. The implications for cross-modal links in spatial attention are discussed.

Attention and the crossmodal construction of space

Traditional studies of spatial attention consider only a single sensory modality at a time (e.g. just vision, or just audition). In daily life, however, our spatial attention often has to be coordinated across several modalities. This is a non-trivial problem, given that each modality initially codes space in entirely different ways. In the last five years, there has been a spate of studies on crossmodal attention. These have demonstrated numerous crossmodal links in spatial attention, such that attending to a particular location in one modality tends to produce corresponding shifts of attention in other modalities. The spatial coordinates of these crossmodal links illustrate that the internal representation of external space depends on extensive crossmodal integration. Recent neuroscience studies are discussed that suggest possible brain mechanisms for the crossmodal links in spatial attention.