Tactile processing is modulated by task-irrelevant visual stimuli in peripersonal but not in extra-personal space: an ERP investigation

Chiara Sambo, Cognitive Neuroscience Research Unit, Department of Psychology, City University, London

Research over the last decades has provided a growing body of evidence supporting the hypothesis of an integrated visuo-tactile network coding for peripersonal space. The present study investigated whether tactile processing is affected by the simultaneous presentation of task-irrelevant visual stimuli in peripersonal and extra-personal space. Participants directed their attention to one of their hands to detect infrequent tactile target stimuli at that hand while ignoring all tactile non-target stimuli; and any visual stimuli in the same or opposite hemispace with respect to the tactile stimuli either in peripersonal or far space. Enhancement of somatosensory ERPs was present as early as 100 ms after onset of tactile stimulus (i.e. overlapping with the P100 component) when visual stimuli were presented next to the site of tactile stimulation compared to when these were presented at different locations in near and far space suggesting that visuo-tactile interactions can affect early somatosensory processing when visual and tactile stimuli are presented at the same location. In contrast, an enhanced N140 component followed by a late negativity were present for tactile stimuli at attended compared to unattended locations irrespective of whether visual stimuli were presented in near or far space. The pattern of these results suggests that visuo-tactile spatial interactions and tactile-spatial attention affect different stages of tactile processing.

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