Cue-locked lateralized components in a tactile spatial attention task: Evidence for a functional dissociation between ADAN and LSN

ERP studies investigating the control processes responsible for spatial orienting in touch have consistently observed that the anterior directing attention negativity (ADAN) elicited by an attention-directing cue is followed by a sustained negativity contralateral to the cued hand. Recent evidence suggested that the later negativity, labelled late somatotopic negativity (LSN), might reflect distinct neuro-cognitive processes from those associated with the ADAN. To investigate the functional meaning of the ADAN and LSN components, we measured event-related brain potentials elicited by bilateral tactile cues indicating to covertly shift tactile attention to the left or right hand. Participants performed two spatial attention tasks which differed only for the difficulty of the target/nontarget discrimination at attended locations. The LSN but not the ADAN was sensitive to our experimental manipulation of task difficulty, suggesting that this component might reflect sensory-specific preparatory processes prior to a forthcoming tactile stimulus.