Lateralized frontal activity elicited by attention-directing visual and auditory cues.

In event-related potential studies of voluntary spatial attention, lateralized activity observed over anterior scalp sites prior to an impending target has been interpreted as the activity of a supramodal attentional control mechanism in the frontal lobes. However, variability in the scalp topography and presence of this activity across studies suggests that multiple neural generators contribute to the lateralized activity recorded at the scalp. Using distributed source modeling we found two distinct frontal lobe sources following attention-directing cues, one dependent on the sensory modality of the eliciting stimulus and one dependent on the response requirements of the task. Differential activity of these sources depending on task parameters suggests that neither source reflects activity necessary for controlling attention.