Sense of Agency - Neuroscience of The Sense of Agency

Neuroscience of The Sense of Agency

A number of experiments in normal individuals has been undertaken in order to determine the functional anatomy of the sense of agency. These experiments have consistently documented the role of the posterior parietal cortex as a critical link within the simulation network for self-recognition. Activation of the right inferior parietal lobe/temporoparietal junction correlates with the subjective sense of ownership in action execution. Posterior parietal lesions, especially on the right side, impair the ability of recognizing one's own body parts and self-attributing one's own movements.

Accumulating evidence from functional neuroimaging studies, as well as lesion studies in neurological patients indicates that the right inferior parietal cortex, at the junction with the posterior temporal cortex (TPJ, temporoparietal junction), plays a critical role in the distinction between self-produced actions and actions perceived in others. Lesions of this region can produce a variety of disorders associated with body knowledge and self-awareness such as anosognosia, asomatognosia, or somatoparaphrenia. Electrical stimulation of the TPJ can elicit out-of-body experiences (i.e., the experience of dissociation of self from the body).

The investigation of the neural correlates of reciprocal imitation is extremely important because it provides an ecological paradigm (a situation close to everyday life) to address the issue of the sense of agency. There is good evidence that reciprocal imitation plays a constitutive role in the early development of an implicit sense of self as a social agent. In one functional neuroimaging experiment, participants were scanned while they imitated an experimenter performing constructions with small objects and while the experimenter, while performing such a manipulation, imitated the participants. Across both conditions, the participants' sense of ownership (the sense that it is I who am experiencing the movement or thought) as well as the visual and somatosensory inputs are similar or coincide. What differs between imitating and being imitated is the agent who initiated the action. Several key regions were involved in the two conditions of reciprocal imitation compared to a control condition (in which subjects acted differently from the experimenter), namely in the superior temporal sulcus, the temporoparietal cortex (TPJ), and the medial prefrontal cortex.

Another approach to understanding the neuroscientific underpinnings of the sense of agency is to examine clinical conditions in which purposeful limb movement occurs without an associated sense of agency. The most clear clinical demonstration of this situation is alien hand syndrome. In this condition, associated with specific forms of brain damage, the affected individual loses the sense of agency without losing a sense of ownership of the affected body part.