“Touched” by Light: Event-Related Potentials (ERPs) to Visuo-Haptic Stimuli in Peri-Personal Space

Abstract

Parietal neuronal populations have been found which respond bimodally to visual and somatosensory input regarding one’s own limbs or even perceived haptic input of a false limb (Graziano et al., 2000). Further, neuronal populations have been observed which respond preferentially to visual stimuli presented in spatial congruence with our hands (Graziano 1999). In this study, we examined event-related potentials (ERPs) elicited by laser dots projected onto or above participants’ index and middle fingers during a sustained-attention task. We hypothesized that visual stimuli projected onto the hand would elicit differences in ERP deflections related to sensory gating and categorization in comparison to when projected close to the hand. Participants responded via a footswitch to rare target flashes of light occurring on or directly above the middle finger of the attended hand. We found enhanced amplitudes of the N1 and P3 deflections when the stimuli fell onto the finger tips as opposed to above them. Furthermore, the N1 for unattended stimuli was less suppressed when the lasers were projected onto the fingers. Behaviorally, participants were less accurate to targets when the lasers fell onto the fingers. We conclude that when the lasers appear to “touch” the participants, they act to automatically draw participants’ attention. Thus visual stimuli projected onto the fingers of the ‘unattended’ hand are harder to filter out, leading to decreases in accuracy during task performance.

Attention's grasp: early and late hand proximity effects on visual evoked potentials

“…Electrode clusters and latency windows were chosen based on those reported in visuo-tactile multisensory integration studies (Kennett et al, 2001; Simon-Dack et al, 2009), visual attention studies (Eimer, 1994), and from an examination of where deflections were most prominent in the grand average waveforms sites from the current data set: P1 (80–110 ms) for lateral parietal-occipital sites (O1/P1/P3; O2/P2/P4), central Nd1 (120–190 ms) for midline parietal-occipital sites (Pz/POz), P3 (350–450 ms,) and a late positivity referred to as the P3Termination or P3T (450–650 ms) for lateral central-parietal sites (FC1/C1/CP1; FC2/C2/CP2). Mean amplitude values were calculated within specified time windows.…”

“…For instance, the Nd1 shows greater amplitudes in a cross-modal cuing task when visual and tactile stimuli were presented than when unimodal stimuli were presented. Likewise, a similar component was found to be enhanced when visual stimuli were presented on the hand for implicit “touch” as opposed to near the hand (Simon-Dack et al, 2009). Finally, the P3 (300–500 ms) reflects discrimination of stimulus categories at a more abstract, task or motivationally relevant level.…”

Visuo-tactile Integration in Personal Space

“…Multisensory interactions appear to become spatially sensitive only 100-200 msec poststimulus, both for effects of hemispace (Gondan, Niederhaus, Rösler, & Röder, 2005;Teder-Sälejärvi, Di Russo, McDonald, & Hillyard, 2005;Eimer & Driver, 2000) and of location in peripersonal space (Sambo & Forster, 2009;Simon-Dack et al, 2009). In contrast, the present results, showing extremely precise spatial congruence effects in personal space, show maximal differences much later.…”

Phantoms on the hands: Influence of the body on brief synchiric visual percepts

“…This enhancement effect loses its spatial specificity after TMS of posterior parietal cortex, providing additional evidence that posterior parietal regions are involved in visuotactile integration. Larger N1 ERP components, indicative of increased processing in occipital brain regions, have been generated for visual stimuli presented on versus above the hands (Simon-Dack, et al, 2009). These studies provide evidence that posterior parietal regions involved in representing touch and the body interact with visual areas, resulting in changes in visual perception.…”