Academic journal article Cognitive, Affective and Behavioral Neuroscience

Electrophysiological Correlates of Crossmodal Visual Distractor Congruency Effects: Evidence for Response Conflict

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Electrophysiological Correlates of Crossmodal Visual Distractor Congruency Effects: Evidence for Response Conflict

Article excerpt

To investigate the basis of crossmodal visual distractor congruency effects, we recorded event-related brain potentials (ERP) while participants performed a tactile location-discrimination task. Participants made speeded tactile location-discrimination responses to tactile targets presented to the index fingers or thumbs while ignoring simultaneously presented task-irrelevant visual distractor stimuli at either the same (congruent) or a different (incongruent) location. Behavioural results were in line with previous studies, showing slowed response times and increased error rates on incongruent compared with congruent visual distractor trials. To clarify the effect of visual distractors on tactile processing, concurrently recorded ERPs were analyzed for poststimulus, preresponse, and postresponse modulations. An enhanced negativity was found in the time range of the N2 component on incongruent compared with congruent visual distractor trials prior to correct responses. In addition, postresponse ERPs showed the presence of error-related negativity components on incorrect-response trials and enhanced negativity for congruent-incorrect compared with incongruent-incorrect trials. This pattern of ERP results has previously been related to response conflict (Yeung, Botvinick, & Cohen, 2004). Importantly, no modulation of early somatosensory ERPs was present prior to the N2 time range, which may have suggested the contribution of other perceptual or postperceptual processes to crossmodal congruency effects. Taken together, our results suggest that crossmodal visual distractor effects are largely due to response conflict.

Investigations into the effects of events in one modality on processing of events in another modality and the integration of information across sensory modalities have recently gained increasing interest (see chapters in Calvert, Spence, & Stein, 2004, and Spence & Driver, 2004). Moreover, investigations into the interactions between visual and tactile events have revealed spatial constraints of peripersonal and extrapersonal space perception (for a review, see Maravita, Spence, & Driver, 2003). Whereas tactile events define our proximal boundaries, visual events can occur close to the body surface or some distance away; furthermore, depending on the perceived distance of visual stimuli from tactile events, visual task-irrelevant stimuli may influence tactile discrimination judgments (for a review, see Spence, Pavani, Maravita, & Holmes, 2004).

Specifically, one paradigm, the visual-tactile crossmcdal distractor congruency task, has been used to investigate the multisensory construction of space (e.g., Maravita et al., 2003). In this paradigm, participants typically hold two cubes, one in either hand. One tactile stimulator and one light-emitting diode (LED) are placed in the upper and lower surface of each cube directly under or close to the index finger and thumb of each hand. On each trial, one tactile target and one visual distractor are presented simultaneously at any one of the four possible locations. The participants' task is to identify the location of the tactile target (top or bottom) while ignoring visual distractors. Visual distractors and tactile targets are presented from either the same location or different locations. Participants are typically slower and less accurate at discriminating the location of vibrotactile targets when simultaneously presented with a visual distractor from a different/incongruent location (i.e., tactile targets are presented at top locations and visual distractors at bottom locations, or vice versa) than they are when both tactile target and visual distractor are presented from the same/congruent location (i.e., either both from the same top location or both from the same bottom location). This difference in performance between incongruent and congruent trials is taken as an indication of visual distractor influence on tactile target discriminations. …

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