Having a body versus moving your body: neural signatures of agency and body-ownership.

The exact relation between the sense that one's body is one's own (body-ownership) and the sense that one controls one's own bodily actions (agency) has been the focus of much speculation, but remains unclear. On an 'additive' model, agency and body-ownership are strongly related; the ability to control actions is a powerful cue to body-ownership. This view implies a component common to the senses of body-ownership and agency, plus possible additional components unique to agency. An alternative 'independence' model holds that agency and body-ownership are qualitatively different experiences, triggered by different inputs, and recruiting distinct brain networks. We tested these two specific models by investigating the sensory and motor aspects of body-representation in the brain using fMRI. Activations in midline cortical structures were associated with a sensory-driven sense of body-ownership, and were absent in agency conditions. Activity in the pre-SMA was linked to the sense of agency, but distinct from the sense of body-ownership. No shared activations that would support the additive model were found. The results support the independence model. Body-ownership involves a psychophysiological baseline, linked to activation of the brain's default mode network. Agency is linked to premotor and parietal areas involved in generating motor intentions and subsequent action monitoring.