ERP investigation of transient attentional selection of single and multiple locations within touch.

Mechanisms underlying pure tactile attentional selection were investigated. Tactile imperative stimuli were preceded by symbolic tactile cues directing attention to the left or right (directional cues), or to both hands (non-directional cues). Comparison of ERP waveforms on directional and non-directional cue trials showed that attentional modulations at N140 and P200 components reflect mainly enhancement of stimuli at the attended, while longer latency modulations reflect mainly suppression of processing of stimuli at the unattended location. This pattern of results differs from analogous studies involving other modalities suggesting that different mechanisms underlie pure tactile attention. Furthermore, ERP waveforms on non-directional cue trials were enhanced in comparison to directional cue trials at the P100 component and at longer latencies, indicating that tactile attentional mechanisms may differ when attending to one compared to multiple locations.