Biomedical subjects

Charles Spence

Publications and source records attributed to Charles Spence.

90 records · Page 5Linked to original sources

PubMed2003

Multisensory temporal order judgments: when two locations are better than one.

In Experiment 1, participants were presented with pairs of stimuli (one visual and the other tactile) from the left and/or right of fixation at varying stimulus onset asynchronies and were required to make unspeeded temporal order judgments (TOJs) regarding which modality was presented first. When the participants adopted an uncrossed-hands posture, just noticeable differences (JNDs) were lower (i.e., multisensory TOJs were more precise) when stimuli were presented from different positions, rather than from the same position. This spatial redundancy benefit was reduced when the participants adopted a crossed-hands posture, suggesting a failure to remap visuotactile space appropriately. In Experiment 2, JNDs were also lower when pairs of auditory and visual stimuli were presented from different positions, rather than from the same position. Taken together, these results demonstrate that people can use redundant spatial cues to facilitate their performance on multisensory TOJ tasks and suggest that previous studies may have systematically overestimated the precision with which people can make such judgments. These results highlight the intimate link between spatial and temporal factors in determining our perception of the multimodal objects and events in the world around us.

Adult↗

PubMed2003

Crossmodal links between audition and touch in covert endogenous spatial attention.

We report three experiments designed to investigate the nature of any crossmodal links between audition and touch in sustained endogenous covert spatial attention, using the orthogonal spatial cuing paradigm. Participants discriminated the elevation (up vs. down) of auditory and tactile targets presented to either the left or the right of fixation. In Experiment 1, targets were expected on a particular side in just one modality; the results demonstrated that the participants could spatially shift their attention independently in both audition and touch. Experiment 2 demonstrated that when the participants were informed that targets were more likely to be on one side for both modalities, elevation judgments were faster on that side in both audition and touch. The participants were also able to "split" their auditory and tactile attention, albeit at some cost, when targets in the two modalities were expected on opposite sides. Similar results were also reported in Experiment 3 when participants adopted a crossed-hands posture, thus revealing that crossmodal links in audiotactile attention operate on a representation of space that is updated following posture change. These results are discussed in relation to previous findings regarding crossmodal links in audiovisual and visuotactile covert spatial attentional orienting.

Adult↗

PubMed2003

Presenting multiple auditory signals using multiple sound cards in Visual Basic 6.0.

In auditory research, it is often desirable to present more than two auditory stimuli at any one time. Although the technology has been available for some time, the majority of researchers have not utilized it. This article provides a simple means of presenting multiple, concurrent, independent auditory events, using two or more different sound cards installed within a single computer. By enabling the presentation of more auditory events, we can hope to gain a better understanding of the cognitive and attentional processes operating under more complex and realistic scenes, such as that embodied by the cocktail party effect. The software requirements are Windows 98SR2/Me/NT4/2000/XP, Visual Basic 6.0, and DirectX 7.0 or above. The hardware requirements are a Pentium II, 128 MB RAM, and two or more different sound cards.

Acoustic Stimulation↗

PubMed2002

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.

Attention↗

PubMed2002

Audiotactile interactions in roughness perception.

The sounds produced when we touch textured surfaces frequently provide information regarding the structure of those surfaces. It has recently been demonstrated that the perception of the texture of the hands can be modified simply by manipulating the frequency content of such touch-related sounds. We investigated whether similar auditory manipulations change people's perception of the roughness of abrasive surfaces (experiment 1). Participants were required to make speeded, forced-choice discrimination responses regarding the roughness of a series of abrasive samples which they touched briefly. Analysis of discrimination errors verified that tactile roughness perception was modulated by the frequency content of the auditory feedback. Specifically, attenuating high frequencies led to a bias towards an increased perception of tactile smoothness. In experiment 2, we replicated the rubbing-hands manipulation of previous experimenters while participants rated either the perceived roughness or wetness of their hands. The wetness scale data replicated the results in the literature, while the roughness scale data replicated the result from experiment 1. A final experiment showed that delaying the auditory feedback from the hand-rubbing reduced the magnitude of this parchment-skin illusion. These experiments demonstrate the dramatic effect that auditory frequency manipulations can have on the perceived tactile roughness and moistness of surfaces, and are consistent with the proposal that different auditory perceptual dimensions may have varying salience for different surfaces.

Adult↗

PubMed2002

Selective attention to pain: a psychophysical investigation.

Laboratory research suggests that the processing of painful stimuli can be modulated by selective attention to a particular sensory modality. However, alternative accounts for previous findings remain possible in terms of task-switching and spatial attention effects. In the present study, we examined whether attention can be selectively directed to the pain modality in order to facilitate the processing of the sensory-discriminative aspects of painful laser heat stimuli when these alternatives were ruled out. Participants made speeded spatial discrimination responses to an unpredictable sequence of painful laser heat and visual stimuli presented on the left forearm. On each trial, a symbolic cue predicted the likely modality for the upcoming target on the majority of trials. Participants responded more rapidly when the target was presented in the expected as opposed to the unexpected modality, demonstrating that selective attention can modulate the processing of painful stimuli. These findings are discussed in relation to contemporary theories of crossmodal attention and multisensory information-processing.

Attention↗

PubMed2002

An integrated microfabricated cell sorter.

We have developed an integrated microfabricated cell sorter using multilayer soft lithography. This integrated cell sorter is incorporated with various microfluidic functionalities, including peristaltic pumps, dampers, switch valves, and input and output wells, to perform cell sorting in a coordinated and automated fashion. The active volume of an actuated valve on this integrated cell sorter can be as small as 1 pL, and the volume of optical interrogation is approximately 100 fL. Different algorithms of cell manipulation, including cell trapping, were implemented in these devices. We have also demonstrated sorting and recovery of Escherichia coli cells on the chip.

Bacteriological Techniques↗

PubMed2002

Assessing the effect of posture change on tactile inhibition-of-return.

If a peripheral target follows an ipsilateral cue with a stimulus-onset-asynchrony (SOA) of 300 ms or more, its detection is delayed compared to a contralateral-cue condition. This phenomena, known as inhibition-of-return (IOR), affects responses to visual, auditory, and tactile stimuli, and is thought to provide an index of exogenous shifts of spatial attention. The present study investigated whether tactile IOR occurs in a somatotopic vs an allocentric frame of reference. In experiment 1, tactile cue and target stimuli were presented to the index and middle fingers of either hand, with the hands positioned in an uncrossed posture (SOA 500 or 1,000 ms). Speeded target detection responses were slowest for targets presented from the cued finger, and were also slower for targets presented to the adjacent finger on the cued hand than to either finger on the uncued hand. The same pattern of results was also reported when the index and middle fingers of the two hands were interleaved on the midline (experiment 2), suggesting that the gradient of tactile IOR surrounding a cued body site is modulated by the somatotopic rather than by the allocentric distance between cue and target.

Adolescent↗

PubMed2002

Tool-use changes multimodal spatial interactions between vision and touch in normal humans.

In a visual-tactile interference paradigm, subjects judged whether tactile vibrations arose on a finger or thumb (upper vs. lower locations), while ignoring distant visual distractor lights that also appeared in upper or lower locations. Incongruent visual distractors (e.g. a lower light combined with upper touch) disrupt such tactile judgements, particularly when appearing near the tactile stimulus (e.g. on the same side of space as the stimulated hand). Here we show that actively wielding tools can change this pattern of crossmodal interference. When such tools were held in crossed positions (connecting the left hand to the right visual field, and vice-versa), the spatial constraints on crossmodal interference reversed, so that visual distractors in the other visual field now disrupted tactile judgements most for a particular hand. This phenomenon depended on active tool-use, developing with increased experience in using the tool. We relate these results to recent physiological and neuropsychological findings.

Adult↗

PubMed2002

The ventriloquist in motion: illusory capture of dynamic information across sensory modalities.

Integrating dynamic information across the senses is crucial to survival. However, most laboratory studies have only examined sensory integration for static events. Here we demonstrate that strong crossmodal integration can also occur for an emergent attribute of dynamic arrays, specifically the direction of apparent motion. The results of the present study show that the perceived direction of auditory apparent motion is strongly modulated by apparent motion in vision, and that both spatial and temporal factors play a significant role in this crossmodal effect. We also demonstrate that a split-brain patient who does not perceive visual apparent motion across the midline is immune to this audiovisual dynamic capture effect, highlighting the importance of motion being experienced in order for this new multisensory illusion to occur.

Acoustic Stimulation↗

PubMed2002

Confusing the mind by crossing the hands.

Observers made temporal order judgements (TOJs) regarding which of two tactile stimuli presented to either hand (at stimulus onset asynchronies of up to 200 ms) occurred first. When the observers' hands were placed in an uncrossed posture (i.e., each hand in its own hemispace), performance was accurate, with a just noticeable difference (JND; the smallest interval which produces 75% correct performance) of 34 ms. By contrast, when the hands were crossed over the midline, performance declined such that 124 ms was needed for accurate performance. In a second experiment, we presented visual instead of tactile stimuli to evaluate the relative contribution of motor and perceptual confusions to the effect. While performance with crossed hands was significantly worse than with uncrossed hands (JND=36 vs. 31 ms, respectively), this difference was negligible compared to that with tactile stimuli. In a third experiment, experienced observers showed a robust crossed-hands deficit which was not improved by using different fingers on either hand. We argue that the decline in tactile discrimination performance when the hands are crossed reflects a failure to represent appropriately near simultaneous bimanual tactile stimuli, and stands in marked contrast to many recent observations of efficient remapping of singly-presented tactile stimuli.

Analysis of Variance↗

PubMed2002

Modality-specific auditory and visual temporal processing deficits.

We studied the attentional blink (AB) and the repetition blindness (RB) effects using an audiovisual presentation procedure designed to overcome several potential methodological confounds in previous cross-modal research. In Experiment 1, two target digits were embedded amongst letter distractors in two concurrent streams (one visual and the other auditory) presented from the same spatial location. Targets appeared in either modality unpredictably at different temporal lags, and the participants' task was to recall the digits at the end of the trial. We evaluated both AB and RB for pairs of targets presented in either the same or different modalities. Under these conditions both AB and RB were observed in vision, AB but not RB was observed in audition, and there was no evidence o

Attention↗

PubMed2002

Seeing your own touched hands in a mirror modulates cross-modal interactions.

In mirror reflections, visual stimuli in near peripersonal space (e.g., an object in the hand) can project the retinal image of far, extrapersonal stimuli "beyond" the mirror. We studied the interaction of such visual reflections with tactile stimuli in a cross-modal congruency task. We found that visual distractors produce stronger interference on tactile judgments when placed close to the stimulated hand, but observed indirectly as distant mirror reflections, than when directly observed in equivalently distant far space, even when in contact with a dummy hand or someone else's hand in the far location. The stronger visual-tactile interference for the mirror condition implies that near stimuli seen as distant reflections in a mirror view of one's own hands can activate neural networks coding peripersonal space, because these visual stimuli are coded as having a true source near to the body.

Adult↗

PubMed2002

Tactile "capture" of audition.

Previous research has demonstrated that the localization of auditory or tactile stimuli can be biased by the simultaneous presentation of a visual stimulus from a different spatial position. We investigated whether auditory localization judgments could also be affected by the presentation of spatially displaced tactile stimuli, using a procedure designed to reveal perceptual interactions across modalities. Participants made left-right discrimination responses regarding the perceived location of sounds, which were presented either in isolation or together with tactile stimulation to the fingertips. The results demonstrate that the apparent location of a sound can be biased toward tactile stimulation when it is synchronous, but not when it is asynchronous, with the auditory event. Directing attention to the tactile modality did not increase the bias of sound localization toward synchronous tactile stimulation. These results provide the first demonstration of the tactile capture of audition.

Adult↗

PubMed2002

Attentional limitations in processing sequentially presented vibrotactile targets.

In seven experiments, participants experienced rapid, serially presented streams of vibrations and responded to specific targets in the streams. In visual (and sometimes auditory) streams presented in this manner, it is typical to find a deficit in reporting the second of two targets when both must be reported and the second appears within a short temporal interval of the first, but not when identical displays are presented but only the second target must be reported (e.g., the attentional blink, or AB). This conventional AB pattern was found in the last experiment, in which judgments were about target location. However in the first six experiments reported here, in which judgments were about frequency, intensity, duration, or location of targets, accuracy was dependent on target separation regardless of whether or not the first target was reported. This unconventional pattern could represent an AB if the first target was attended even when it was not reported. The evidence for this claim and an alternative possibility that location judgments are especially sensitive to attention manipulations are discussed.

Adolescent↗

PubMed2002

Visuo-tactile links in covert exogenous spatial attention remap across changes in unseen hand posture.

We investigated the effect of unseen hand posture on cross-modal, visuo-tactile links in covert spatial attention. In Experiment 1, a spatially nonpredictive visual cue was presented to the left or right hemifield shortly before a tactile target on either hand. To examine the spatial coordinates of any cross-modal cuing, the unseen hands were either uncrossed or crossed so that the left hand lay to the right and vice versa. Tactile up/down (i.e., index finger/thumb) judgments were better on the same side of external space as the visual cue, for both crossed and uncrossed postures. Thus, which hand was advantaged by a visual cue in a particular hemifield reversed across the different unseen postures. In Experiment 2, nonpredictive tactile cues now preceded visual targets. Up/down judgments for the latter were better on the same side of external space as the tactile cue, again for both postures. These results demonstrate cross-modal links between vision and touch in exogenous covert spatial attention that remap across changes in unseen hand posture, suggesting a modulatory role for proprioception.

Adolescent↗

PubMed2002

A crossmodal attentional blink between vision and touch.

There is currently a great deal of interest regarding the possible existence of a crossmodal attentional blink (AB) between audition and vision. The majority of evidence now suggests that no such crossmodal deficit exists unless a task switch is introduced. We report two experiments designed to investigate the existence of a crossmodal AB between vision and touch. Two masked targets were presented successively at variable interstimulus intervals. Participants had to respond either to both targets (experimental condition) or to just the second target (control condition). In Experiment 1, the order of target modality was blocked, and an AB was demonstrated when visual targets preceded tactile targets, but not when tactile targets preceded visual targets. In Experiment 2, target modality was mixed randomly, and a significant crossmodal AB was demonstrated in both directions between vision and touch. The contrast between our visuotactile results and those of previous audiovisual studies is discussed, as are the implications for current theories of the AB.

Adult↗

PubMedDate not supplied

Multisensory contributions to the 3-D representation of visuotactile peripersonal space in humans: evidence from the crossmodal congruency task.

In order to determine precisely the location of a tactile stimulus presented to the hand it is necessary to know not only which part of the body has been stimulated, but also where that part of the body lies in space. This involves the multisensory integration of visual, tactile, proprioceptive, and even auditory cues regarding limb position. In recent years, researchers have become increasingly interested in the question of how these various sensory cues are weighted and integrated in order to enable people to localize tactile stimuli, as well as to give rise to the 'felt' position of our limbs, and ultimately the multisensory representation of 3-D peripersonal space. We highlight recent research on this topic using the crossmodal congruency task, in which participants make speeded elevation discrimination responses to vibrotactile targets presented to the thumb or index finger, while simultaneously trying to ignore irrelevant visual distractors presented from either the same (i.e., congruent) or a different (i.e., incongruent) elevation. Crossmodal congruency effects (calculated as performance on incongruent-congruent trials) are greatest when visual and vibrotactile stimuli are presented from the same azimuthal location, thus providing an index of common position across different sensory modalities. The crossmodal congruency task has been used to investigate a number of questions related to the representation of space in both normal participants and brain-damaged patients. In this review, we detail the major findings from this research, and highlight areas of convergence with other cognitive neuroscience disciplines.

Animals↗