Tactile Distractors Research Articles

Tactile processing in mouse cortex depends on action context

The brain receives constant tactile input, but only a subset guides ongoing behavior. Actions associated with tactile stimuli thus endow them with behavioral relevance. It remains unclear how the relevance of tactile stimuli affects processing in the somatosensory (S1) cortex. We developed a cross-modal selection task in which head-fixed mice switched between responding to tactile stimuli in the presence of visual distractors or to visual stimuli in the presence of tactile distractors using licking movements to the left or right side in different blocks of trials. S1 spiking encoded tactile stimuli, licking actions, and direction of licking in response to tactile but not visual stimuli. Bidirectional optogenetic manipulations showed that sensory-motor activity in S1 guided behavior when touch but not vision was relevant. Our results show that S1 activity and its impact on behavior depend on the actions associated with a tactile stimulus.

Little engagement of attention by salient distractors defined in a different dimension or modality to the visual search target.

Singleton distractors may inadvertently capture attention, interfering with the task at hand. The underlying neural mechanisms of how we prevent or handle distractor interference remain elusive. Here, we varied the type of salient distractor introduced in a visual search task: the distractor could be defined in the same (shape) dimension as the target, a different (color) dimension, or a different (tactile) modality (intra-dimensional, cross-dimensional, and, respectively, cross-modal distractor, all matched for physical salience); and besides behavioral interference, we measured lateralized electrophysiological indicators of attentional selectivity (the N2pc, Ppc, PD , CCN/CCP, CDA, and cCDA). The results revealed the intra-dimensional distractor to produce the strongest reaction-time interference, associated with the smallest target-elicited N2pc. In contrast, the cross-dimensional and cross-modal distractors did not engender any significant interference, and the target-elicited N2pc was comparable to the condition in which the search display contained only the target singleton, thus ruling out early attentional capture. Moreover, the cross-modal distractor elicited a significant early CCN/CCP, but did not influence the target-elicited N2pc, suggesting that the tactile distractor is registered by the somatosensory system (rather than being proactively suppressed), without, however, engaging attention. Together, our findings indicate that, in contrast to distractors defined in the same dimension as the target, distractors singled out in a different dimension or modality can be effectively prevented to engage attention, consistent with dimension- or modality-weighting accounts of attentional priority computation.

Statistical context learning in tactile search: Crossmodally redundant, visuo-tactile contexts fail to enhance contextual cueing

In search tasks, reaction times become faster when the target is repeatedly encountered at a fixed position within a consistent spatial arrangement of distractor items, compared to random arrangements. Such “contextual cueing” is also obtained when the predictive distractor context is provided by a non-target modality. Thus, in tactile search, finding a target defined by a deviant vibro-tactile pattern (delivered to one fingertip) from the patterns at other, distractor (fingertip) locations is facilitated not only when the configuration of tactile distractors is predictive of the target location, but also when a configuration of (collocated) visual distractors is predictive—where intramodal-tactile cueing is mediated by a somatotopic and crossmodal-visuotactile cueing by a spatiotopic reference frame. This raises the question of whether redundant multisensory, tactile-plus-visual contexts would enhance contextual cueing of tactile search over and above the level attained by unisensory contexts alone. To address this, we implemented a tactile search task in which, in 50% of the trials in a “multisensory” phase, the tactile target location was predicted by both the tactile and the visual distractor context; in the other 50%, as well as a “unisensory” phase, the target location was solely predicted by the tactile context. We observed no redundancy gains by multisensory-visuotactile contexts, compared to unisensory-tactile contexts. This argues that the reference frame for contextual learning is determined by the task-critical modality (somatotopic coordinates for tactile search). And whether redundant predictive contexts from another modality (vision) can enhance contextual cueing depends on the availability of the corresponding spatial (spatiotopic-visual to somatotopic-tactile) remapping routines.

Attentional interference by pain in a dishabituation procedure: an experimental investigation.

The ability to habituate to pain may be adaptive, and it may enable us to pursue valuable goals despite the pain. In this study, we experimentally investigated this idea using the primary task paradigm in which participants had to identify the color of a circle (blue or yellow) as quickly as possible while ignoring painful or tactile distractors that are presented on some of the trials. In the first experiment, we were interested whether the attentional interference effect because of the presentation of the distractors and its habituation would differ between painful and tactile distractor stimuli. In the second experiment, we investigated dishabituation (ie, the phenomenon that the introduction of a different stimulus results in an increase of the decremented response to the original stimulus). We expected habituation of the attentional interference to occur both in the tactile and the painful distractor condition, but to be less complete in the painful condition. Moreover, we hypothesized that the dishabituation would be stronger for the painful than for the tactile distractors. We did find evidence for an interference effect because of the presence of distractors. We also found habituation of attentional interference. However, the interference and its habituation were no different for tactile and painful distractors. Moreover, we did not find evidence for dishabituation. These are the first studies of their kind. Implications and guidelines for future research are formulated.

Crossmodal learning of target-context associations: When would tactile context predict visual search?

It is well established that statistical learning of visual target locations in relation to constantly positioned visual distractors facilitates visual search. In the present study, we investigated whether such a contextual-cueing effect would also work crossmodally, from touch onto vision. Participants responded to the orientation of a visual target singleton presented among seven homogenous visual distractors. Four tactile stimuli, two to different fingers of each hand, were presented either simultaneously with or prior to the visual stimuli. The identity of the stimulated fingers provided the crossmodal context cue: in half of the trials, a given visual target location was consistently paired with a given tactile configuration. The visual stimuli were presented above the unseen fingers, ensuring spatial correspondence between vision and touch. We found no evidence of crossmodal contextual cueing when the two sets of items (tactile, visual) were presented simultaneously (Experiment 1). However, a reliable crossmodal effect emerged when the tactile distractors preceded the onset of visual stimuli 700 ms (Experiment 2). But crossmodal cueing disappeared again when, after an initial learning phase, participants flipped their hands, making the tactile distractors appear at different positions in external space while their somatotopic positions remained unchanged (Experiment 3). In all experiments, participants were unable to explicitly discriminate learned from novel multisensory arrays. These findings indicate that search-facilitating context memory can be established across vision and touch. However, in order to guide visual search, the (predictive) tactile configurations must be remapped from their initial somatotopic into a common external representational format.

Multisensory distractor processing is modulated by spatial attention.

To respond to multisensory information, inputs from different sensory modalities must be processed and combined. Recently, overt spatial attention was shown to be a crucial factor modulating the processing of irrelevant audiovisual multisensory stimuli. Here, we investigate the processing of task-irrelevant visuotactile features in a multisensory flanker interference task incorporating visuotactile target and distractor stimuli. The congruency between the target and distractor features was varied orthogonally. Across three experiments, overt spatial attention and the spatial separation between the distractor and the target were varied systematically. When fixating the distractor, the processing of the visual and tactile distractor features was not independent. Manipulating overt spatial attention as well as the spatial separation between the target and distractor impacted multisensory distractor processing. These results are consistent with those approaches emphasizing the role of attention in multisensory processing specifically in relation to the cognitive load or selection difficulty of the task situation. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Pain and Distraction According to Sensory Modalities: Current Findings and Future Directions.

This review discusses the findings in the literature on pain and distraction tasks according to their sensory modality. Distraction tasks have been shown to reduce (experimentally induced) acute pain and chronic pain. This can be influenced by nature and by the sensory modalities used in the distraction tasks. Yet the effect on reducing pain according to the sensory modality of the distraction task has received little attention. A bibliographic search was performed in different databases. The studies will be systematized according to the sensory modality in which the distraction task was applied. The analyzed studies with auditory distractors showed a reduction of acute pain in adults. However, these are not effective at healthy children and in adults with chronic pain. Visual distractors showed promising results in acute pain in adults and children. Similarly, tactile and mixed distractors decreased acute pain in adults. Distraction tasks by diverse sensory modalities have a positive effect on decreasing the perception of acute pain in adults. Future studies are necessary given the paucity of research on this topic, particularly with tactile distractors (there is only one study). Finally, the most rigorous methodology and the use of ecological contexts are encouraged in future research.

Separating after-effects of target and distractor processing in the tactile sensory modality.

The present study investigated the cognitive mechanisms underlying aftereffects of tactile target and distractor processing. In our experiment, participants selected tactile target stimuli against simultaneously presented tactile distractor stimuli in prime-probe sequences. Tactile distractors in each prime/probe trial were either response incompatible (i.e., interfering at the response level) or response neutral (i.e., noninterfering at the response level), manipulated between participants. Furthermore, distractor relation (repetition vs. change) and response relation (repetition vs. change) across prime-probe sequences were orthogonally varied within participants. Thus, independent estimates of distractor repetition main effects (that are attributable to distractor-specific prime processing and have previously been interpreted in terms of inhibition or episodic retrieval processes) and the modulation of distractor repetition effects due to response relation (that is target specific and can only be explained in terms of event-file retrieval) were assessed (see Giesen, Frings, & Rothermund, Memory & Cognition, 40, 373-387, 2012). Replicating previous studies with visual stimuli, simple distractor repetition effects were stronger for response-incompatible compared with response-neutral tactile distractors. In contrast, event-file retrieval as reflected in distractor-response binding retrieval effects was not modulated by whether the distractors were response incompatible or response neutral. Together, these findings highlight that in tactile tasks, prime-distractor and prime-target processing both hold the potential to cause aftereffects during probe performance.

Effects of visual and tactile distractors on eye and hand movement curvature

Effects of visual and tactile distractors on eye and hand movement curvature

Task demands affect spatial reference frame weighting during tactile localization in sighted and congenitally blind adults.

Task demands modulate tactile localization in sighted humans, presumably through weight adjustments in the spatial integration of anatomical, skin-based, and external, posture-based information. In contrast, previous studies have suggested that congenitally blind humans, by default, refrain from automatic spatial integration and localize touch using only skin-based information. Here, sighted and congenitally blind participants localized tactile targets on the palm or back of one hand, while ignoring simultaneous tactile distractors at congruent or incongruent locations on the other hand. We probed the interplay of anatomical and external location codes for spatial congruency effects by varying hand posture: the palms either both faced down, or one faced down and one up. In the latter posture, externally congruent target and distractor locations were anatomically incongruent and vice versa. Target locations had to be reported either anatomically (“palm” or “back” of the hand), or externally (“up” or “down” in space). Under anatomical instructions, performance was more accurate for anatomically congruent than incongruent target-distractor pairs. In contrast, under external instructions, performance was more accurate for externally congruent than incongruent pairs. These modulations were evident in sighted and blind individuals. Notably, distractor effects were overall far smaller in blind than in sighted participants, despite comparable target-distractor identification performance. Thus, the absence of developmental vision seems to be associated with an increased ability to focus tactile attention towards a non-spatially defined target. Nevertheless, that blind individuals exhibited effects of hand posture and task instructions in their congruency effects suggests that, like the sighted, they automatically integrate anatomical and external information during tactile localization. Moreover, spatial integration in tactile processing is, thus, flexibly adapted by top-down information—here, task instruction—even in the absence of developmental vision.

Expected but omitted stimuli affect crossmodal interaction

One of the most important ability of our brain is to integrate input from different sensory modalities to create a coherent representation of the environment. Does expectation affect such multisensory integration? In this paper, we tackled this issue by taking advantage from the crossmodal congruency effect (CCE). Participants made elevation judgments to visual target while ignoring tactile distractors. We manipulated the expectation of the tactile distractor by pairing the tactile stimulus to the index finger with a high-frequency tone and the tactile stimulus to the thumb with a low-frequency tone in 80% of the trials. In the remaining trials we delivered the tone and the visual target, but the tactile distractor was omitted (Study 1). Results fully replicated the basic crossmodal congruency effect. Strikingly, the CCE was observed, though at a lesser degree, also when the tactile distractor was not presented but merely expected. The contingencies between tones and tactile distractors were reversed in a follow-up study (Study 2), and the effect was further tested in two conceptual replications using different combinations of stimuli (Studies 5 and 6). Two control studies ruled out alternative explanations of the observed effect that would not involve a role for tactile distractors (Studies 3, 4). Two additional control studies unequivocally proved the dependency of the CCE on the spatial and temporal expectation of the distractors (Study 7, 8). An internal small-scale meta-analysis showed that the crossmodal congruency effect with predicted distractors is a robust medium size effect. Our findings reveal that multisensory integration, one of the most basic and ubiquitous mechanisms to encode external events, benefits from expectation of sensory input.

Gating at early cortical processing stages is associated with changes in behavioural performance on a sensory conflict task

While there is evidence to show early enhancement of modality-specific somatosensory cortical event-related potentials (ERP) when two stimuli are task-relevant, less is understood about the cortical and behavioural correlates of early modality-specific sensory gating. This study sought to understand how attentional gating affects cortical processing of visual and tactile stimuli at early stages of modality-specific representation. Specifically, alterations in early somatosensory and visual processing based on attentional relevance were examined, along with the effect of an unattended sensory stimulus on cortical processing and behavioural performance. Electroencephalography (EEG) was collected from healthy participants as they performed a sensory selection task. This task required participants to make a scaled motor response to the amplitudes of visual and tactile stimuli presented individually or concurrently. Results showed that the somatosensory N70 ERP was significantly attenuated when tactile stimuli were unattended. When visual stimuli were unattended, modulation of visual potentials occurred later, at the visual P2 potential. Since unattended tactile stimuli were gated at early cortical processing stages, when they were used as distractors, no changes in cortical responses to target stimuli were observed. Additionally, there was no decrease in task accuracy when grading attended stimuli in the presence of a tactile distractor. However, since early gating was not observed in the visual modality, a visual stimulus used as an unattended distractor resulted in smaller-amplitude cortical responses to attended tactile stimuli and less accurate task performance when grading attended stimuli. In conclusion, this study suggests that early gating of unattended stimuli supports modality-specific cortical processing of target stimuli and maintains behavioural task performance.

Saccade trajectories deviate away from spatial, and not retinal, location of nearby tactile distractors

Saccade trajectories deviate away from spatial, and not retinal, location of nearby tactile distractors

Vision of embodied rubber hands enhances tactile distractor processing.

Previous research has demonstrated that viewing one's hand can induce tactile response compatibility effects at the hands. Here, we investigated the question of whether vision of one's own hand is actually necessary. The Eriksen flanker task was combined with the rubber hand illusion in order to determine whether tactile distractors presented to the hand would be processed up to the level of response selection when a pair of rubber hands was seen (while one's own hands were not). Our results demonstrate that only if the rubber hands are perceived as belonging to one's own body, is enhanced distractor processing (up to the level of response selection) observed at the hands. In conclusion, vision of a pair of fake hands enhances tactile distractor processing at the hands if, and only if, it happens to be incorporated into the body representation.

You can't ignore what you can't separate: the effect of visually induced target-distractor separation on tactile selection.

Research suggests that vision of the body-part that happens to receive a tactile event enhances the processing of this stimulus. However, it would appear that only tactile distractors delivered to visible body-parts are processed up to the level of response selection. Here, we analyze whether vision or higher order cognitive processes influence the processing of tactile distractors. We compared the processing of distractors in a tactile variant of the Eriksen flanker task when the body-parts receiving target and distractor stimuli were separated by different types of barriers. Surprisingly, an impermeable barrier prevented tactile distractors from being processed up to the response level, irrespective of whether the barrier was transparent or opaque. By contrast, when an empty frame was placed between the participant's hands, distractors were processed up to the level of response selection. Hence, higher order cognition (here the visually induced representation of the target-distractor separation) influences the processing of tactile distractors. We discuss these results in the light of related findings from selective reaching experiments as well as in terms of Gestalt grouping.

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.

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.

When vision influences the invisible distractor: Tactile response compatibility effects require vision.

Research on the nature of crossmodal interactions between vision and touch has shown that even task-irrelevant visual information can support the processing of tactile targets. In the present study, we implemented a tactile variant of the Eriksen flanker task to investigate the influences of vision on the processing of tactile distractors. In particular, we analyzed whether the size of the flanker effect at the level of perceptual congruency and at the level of response compatibility would differ as a function of the availability of vision (Experiments 1 and 2). Tactile distractors were processed up to the level of response selection only if visual information was provided (i.e., no flanker effects were observed at the level of response compatibility for blindfolded participants). In Experiment 3, we manipulated whether the part of the body receiving the tactile target or distractor was visible, while the other body part was occluded from view. Flanker effects at the level of response compatibility were observed in both conditions, meaning that vision of either the body part receiving the tactile target or the body part receiving the tactile distractor was sufficient to further the processing of tactile distractors from the level of perceptual congruency to the level of response selection. Taken together, these results suggest that vision modulates tactile distractor processing because it results in the processing of tactile distractors up to the level of response selection.

Vision affects tactile target and distractor processing even when space is task-irrelevant

The human brain is adapted to integrate the information from multiple sensory modalities into coherent, robust representations of the objects and events in the external world. A large body of empirical research has demonstrated the ubiquitous nature of the interactions that take place between vision and touch, with the former typically dominating over the latter. Many studies have investigated the influence of visual stimuli on the processing of tactile stimuli (and vice versa). Other studies, meanwhile, have investigated the effect of directing a participant’s gaze either toward or else away from the body-part receiving the target tactile stimulation. Other studies, by contrast, have compared performance in those conditions in which the participant’s eyes have been open versus closed. We start by reviewing the research that has been published to date demonstrating the influence of vision on the processing of tactile targets, that is, on those stimuli that have to be attended or responded to. We outline that many – but not all – of the visuotactile interactions that have been observed to date may be attributable to the direction of spatial attention. We then move on to focus on the crossmodal influence of vision, as well as of the direction of gaze, on the processing of tactile distractors. We highlight the results of those studies demonstrating the influence of vision, rather than gaze direction (i.e., the direction of overt spatial attention), on tactile distractor processing (e.g., tactile variants of the negative-priming or flanker task). The conclusion is that no matter how vision of a tactile distractor is engaged, the result would appear to be the same, namely that tactile distractors are processed more thoroughly.

Spatial references and audio-tactile interaction in cross-modal dynamic capture.

In audiotactile dynamic capture, judgment of the direction of an apparent motion stream (such as auditory motion) was impeded (hence 'captured') by the presentation of a concurrent, but directionally opposite apparent motion stream (such as tactile motion) from a distractor modality, leading to a cross-modal dynamic capture (CDC) effect. That is to say, the percentage of correct reporting of the direction of the target motion was reduced. Previous studies have revealed the effect of stimulus onset asynchronies (SOAs) and the potential spatial remapping (by adopting a cross-hands posture) in CDC. However, further exploration of the dynamic capture process under different postures was not available due to the fact that only two levels of time asynchronies were employed (either synchronous or with an SOA of 500 ms). This study introduced a broad range of SOAs (-400 ms to 400 ms, tactile stream preceded auditory stream or vice versa) to explore the time course of audio-tactile interaction in CDC with two spatial references--arms-uncrossed or arms-crossed postures. Participants judged the direction of auditory apparent motion with tactile distractors. The results showed that in the arms-uncrossed condition, the CDC effect was prominent when the auditory-tactile events were in the temporal integration window (0-60 ms). However, with a preceding tactile cueing effect of SOA equal to and above 150 ms, the CDC effect was reduced, and no CDC effect was observed with the arms-crossed posture. These results suggest CDC effect is modulated by both cross-modal interaction and the spatial reference (especially for the distractors). The magnitude of the CDC effects in audiotactile interaction may be accounted for by reliability of tactile spatial-temporal information.