Neural mechanisms mediating voluntary shifts of spatial attention

The neural mechanisms underlying voluntary shifts of spatial attention were investigated by examining the event-related potentials (ERPs) to attention-directing cues and associated changes in alpha-band (8-14 Hz) electroencephalographic (EEG) activity. Intramodal auditory and visual shifts of attention were examined in Experiments 1 and 2, and crossmodal shifts of attention were examined in Experiments 3 and 4. Different patterns of ERP and alpha-band activities were observed across the four experiments. Frontal ERP activity (ADAN) was elicited by visual cues but not by auditory cues, which disconfirms previous claims t hat that this frontal activity reflects supramodal attentional control processes. Posterior ERP activity (LDAP) and associated changes in alpha-band EEG oscillations were observed in all experiments, but the scalp topographies of these activities depended on the modality of the task-relevant target. Such topographic differences suggest that the posterior ERP and alpha-band activities reflect attentional preparation in sensory-specific regions of cortex.