Executive control, willed actions, and nonconscious processing.

Neuroimaging studies have identified a number of cortical areas involved in the executive control of conscious actions. The areas most frequently implicated are prefrontal and cingulate cortices. Evidence suggests that both of these areas may be essential for executive control of willed action. Prefrontal cortex, however, may be responsible for the initial processing. Executive control is usually discussed with reference to willed actions and is assumed to regulate complex cognitive responses. Although many implicit processes involve complex responses, it is not known whether these actions are also controlled by executive processes. Significantly, some implicit tasks like those involving motor sequence learning and cross-modality priming activate the same areas of prefrontal cortex that are implicated in the executive control of willed actions. It is, however, not clear whether a single executive process controls both implicit and explicit processes, or the implicit processes are regulated by a separate set of executive control having distinct neuroanatomical location and processing properties.