Abstract& Recent behavioral and event-related brain potential (ERP) studies have revealed cross-modal interactions in endogenous spatial attention between vision and audition, plus vision and touch. The present ERP study investigated whether these interactions reflect supramodal attentional control mechanisms, and whether similar cross-modal interactions also exist between audition and touch. Participants directed attention to the side indicated by a cue to detect infrequent auditory or tactile targets at the cued side. The relevant modality (audition or touch) was blocked. Attentional control processes were reflected in systematic ERP modulations elicited during cued shifts of attention. An anterior negativity contralateral to the cued side was followed by a contralateral positivity at posterior sites. These effects were similar whether the cue signaled which side was relevant for audition or for touch. They also resembled previously observed ERP modulations for shifts of visual attention, thus implicating supramodal mechanisms in the control of spatial attention. Following each cue, single auditory, tactile, or visual stimuli were presented at the cued or uncued side. Although stimuli in task-irrelevant modalities could be completely ignored, visual and auditory ERPs were nevertheless affected by spatial attention when touch was relevant, revealing cross-modal interactions. When audition was relevant, visual ERPs, but not tactile ERPs, were affected by spatial attention, indicating that touch can be decoupled from cross-modal attention when task-irrelevant. &

The N2pc component has recently become a popular tool in attention research. To investigate whether this component exclusively reflects attentional target selection, or also prior stages in attentional processing (covert orienting, target-unspecific spatial attention), a spatial cueing procedure was combined with a visual search task. In some blocks, informative cues indicated the side of upcoming singleton targets that were present on most trials among uniform distractors. In other blocks, cues were spatially uninformative, and no preparatory shifts of attention were possible. The N2pc in response to targets was unaffected by this manipulation, showing that this component is not associated with attention shifts. Following informative cues, an attenuated N2pc was elicited by uniform non-target arrays, suggesting that the N2pc may also reflect spatially specific processing of stimulus features at task-relevant locations prior to target selection.Over the past thirty years, the brain mechanisms underlying visual-spatial attention have been studied intensively with event-related brain potential (ERP) measures. Different ERP components have been found to be modulated during spatially selective visual processing, and these components have been linked to different underlying sub-processes of spatial attention. The first type of attention-sensitive ERP effect was uncovered in early ERP studies where participants were instructed to direct their attention to a specific location on the left or right side, and keep it focused for an entire experimental block in order to detect target stimuli at that location (cf., Eason, 1981). Visual stimuli presented within the current focus of spatial attention triggered enhanced sensory-specific visual P1 and N1 components at posterior electrodes. Analogous P1 and N1 amplitude modulations were also observed when attention was manipulated in a trial-by-trial fashion by spatial precues that were presented at the start of each trial (cf. Mangun & Hillyard, 1991;Eimer, 1994). Because these P1/N1 enhancements for stimuli at attended locations were present irrespective of whether these stimuli were targets or non-targets (e.g., Mangun & Hillyard, 1987), they are interpreted as reflecting location-specific sensory gating mechanisms in early visual processing that precede the subsequent selection of targets over non-targets. They are assumed to be triggered by top-down signals from higher-order attentional control areas that bias the excitability of visual cortical areas in favour of any sensory input that originates from currently task-relevant locations (cf., Mangun, 1995).Other attention-sensitive ERP modulations found in more recent studies during cued shifts of spatial attention were interpreted as electrophysiological markers of top-down attentional control processes. In these studies, ERP components sensitive to the direction of cued attentional shifts were quantified by comparing ERP waveforms triggered in the interval

Previous experiments investigating ERP correlates of anticipatory attention shifts triggered by central symbolic cues have identified a contralateral "early directing attention negativity," which was assumed to be generated by processes involved in the control of spatial orienting. Here we demonstrate that this component is not directly linked to the control of attentional shifts, but instead reflects the selection of task-relevant aspects of cue stimuli. In contrast, later ERP components triggered during covert attentional shifts are insensitive to physical cue attributes, and thus appear to be genuine electrophysiological correlates of covert attentional control mechanisms.

To investigate whether processes controlling preparatory covert shifts of spatial attention operate within external and anatomically defined spatial coordinates, lateralized event-related potentials components sensitive to the direction of attentional shifts were measured in response to visual precues directing attention to the relevant location of tactile events. Participants had to detect infrequent tactile targets delivered to the hand located on the cued side. In different blocks, hands were uncrossed or crossed, so that external and anatomical codes specifying task-relevant locations were either congruent or incongruent. With uncrossed hands, an anterior directing attention negativity and a posterior directing attention positivity were elicited in the cue-target interval contralateral to the side of a cued attentional shift. Although the posterior effect was unaffected by hand posture, the anterior effect was delayed and reversed polarity with crossed relative to uncrossed hands. This pattern of results provides new evidence that different spatial coordinate systems may be used by separable attentional control processes. It is suggested that a posterior process operates on the basis of external spatial coordinates, whereas an anterior process is based primarily on anatomically defined spatial codes.

When we sense a touch, our brains take account of our current limb position to determine the location of that touch in external space [1, 2]. Here we show that changes in the way the brain processes somatosensory information in the first year of life underlie the origins of this ability [3]. In three experiments we recorded somatosensory evoked potentials (SEPs) from 6.5-, 8-, and 10-month-old infants while presenting vibrotactile stimuli to their hands across uncrossed- and crossed-hands postures. At all ages we observed SEPs over central regions contralateral to the stimulated hand. Somatosensory processing was influenced by arm posture from 8 months onward. At 8 months, posture influenced mid-latency SEP components, but by 10 months effects were observed at early components associated with feed-forward stages of somatosensory processing. Furthermore, sight of the hands was a necessary pre-requisite for somatosensory remapping at 10 months. Thus, the cortical networks [4] underlying the ability to dynamically update the location of a perceived touch across limb movements become functional during the first year of life. Up until at least 6.5 months of age, it seems that human infants' perceptions of tactile stimuli in the external environment are heavily dependent upon limb position.