Covert attention in touch: behavioral and ERP evidence for costs and benefits

To investigate the mechanism underlying tactile spatial attention, reaction times (RTs) and event-related potentials (ERPs) were recorded in response to mechanical stimuli delivered to the hands. At the start of each trial cues indicated either the correct (valid) or incorrect (invalid) tactile stimulus location or were uninformative (neutral). RT costs (suppression of invalid compared to neutral trials) were found to be larger than benefits (enhancement of valid compared to neutral trials). ERPs showed that costs and benefits contribute equally to attentional modulations of the somatosensory N140 component, whereas these were largely due to costs at longer latencies. These results differ from the pattern of attentional ERP modulations previously found for vision and audition, where costs precede benefits, and therefore suggest that the mechanisms of attentional selectivity in touch might be different from attentional processes in other modalities.