Isolating event-related potential components associated with voluntary control of visuo-spatial attention.

Attention-directing cues presented at fixation evoke several lateralized event-related potential (ERP) components prior to the onset of visual targets. These components have been associated with the control of visuo-spatial attention, but the neuro-cognitive operations and neural generators of the components are still largely unknown. Here, we isolated cue-elicited ERP activity in different ways to home in on different neuro-cognitive operations and to gain a better understanding about the possible neuroanatomical sources of the cue-elicited ERP activities. To isolate lateralized cue-ERP activity, we compared shift-left and shift-right cue ERPs to shift-up cue ERPs. To measure all of the ERP activity related to attentional control, including spatially nonspecific activity that is removed in the process of isolating lateralized cue-ERP components, we compared shift-cue ERPs to neutral-cue (i.e., no-shift) ERPs. Isolated lateralized-ERP activity was seen in the contralateral-occipital lobe in the early phase of the cue-target interval and in the ipsilateral-occipital lobe in the late phase. The later, ipsilateral activity indicates that the late directing attention positivity (LDAP) reflected processing of the to-be-ignored location. The neutral-cue isolation revealed a shift-related positivity over posterior scalp regions and a shift-related negativity over more anterior scalp regions. The spatio-temporal sequence of shift-related activity observed on the scalp, together with estimates of distributed source activity underlying the shift-related ERP components, indicated that frontal and parietal regions of cortex participated in the control of attention and led to pre-target biasing in visual cortical areas.