Tactile-visual links in exogenous spatial attention under different postures: Convergent evidence from psychophysics and ERPs

Tactile-visual links in spatial attention were examined by presenting spati ally nonpredictive tactile cues to the left or right hand, shortly prior to visual targets in the left or right hemifield. To examine the spatial coor dinates of any crossmodal links, different postures were examined. The hand s were either uncrossed, or crossed so that the left hand lay in the right visual field and vice versa. Visual judgments were better on the side where the stimulated hand lay, though this effect was somewhat smaller with long er intervals between cue and target, and with crossed hands. Event-related brain potentials (ERPs) showed a similar pattern. Larger amplitude occipita l N1 components were obtained for visual events on the same side as the pre ceding tactile cue, at ipsilateral electrode sites. Negativities in the Nd2 interval at midline and lateral central sites, and in the Nd1 interval at electrode Pz, were also enhanced for the cued side. As in the psychophysica l results, ERP cueing effects during the crossed posture were determined by the side of space in which the stimulated hand lay, not by the anatomical side of the initial hemispheric projection for the tactile cue. These resul ts demonstrate that crossmodal links in spatial attention can influence sen sory brain responses as early as the N1, and that these links operate in a spatial frame-of-reference that can remap between the modalities across cha nges in posture.