Spatial attention affects the processing of tactile and visual stimuli presented at the tip of a tool: an event-related potential study.

An event-related potential (ERP) experiment was conducted in order to investigate the nature of any cross-modal links in spatial attention during tool use. Tactile stimuli were delivered from the tip of two sticks, held in either a crossed or an uncrossed tools posture, while visual stimuli were presented along the length of each tool. Participants had to detect tactile deviant stimuli at the end of one stick while trying to ignore all other stimuli. Reliable ERP spatial attention effects to tactile stimuli were observed at early (160-180 ms) and later time epochs (>350 ms) when the tools were uncrossed. Reliable ERP attention effects to visual stimuli presented close to the tip of the tool and close to the hand were also observed in the uncrossed tools condition (time epoch 140-180 ms). These results are consistent with the claim that tool-use results in a shift of visuospatial attention toward the tip of the tool and also to attention being focused by the hand where the touch is felt.