As previously reported, the mirror neuron system is a set of cortical circuits that are active both when an individual performs an act (picking up an apple, say) and when he observes that action being performed by another individual. This collection of cells is clearly important for understanding the intentions of others, and perhaps for learning by imitation. Furthermore, there is quite similar sensory activity associated with both active and passive limb movement (movement imposed on one’s body).
This presents a problem. How do we attribute self-agency to our actions? This is a particularly important question if one subscribes to the theory (mentioned sporadically in this forum), that free will is not the cause of our actions, but the post-hoc assumption of agency for our actions. Even if one does take the stance that free will is the subjective experience of causing thoughts and acts, this question remains relevant since there must be some neural activity which distinguishes self-caused action from passively experienced action.
Of course, there is a wealth of non-cortical activity which accompanies moving one’s arm (signals in the brain-stem and spinal column, in particular) which could provide this signal. However, because of the abstract nature of agency, some have the opinion that there must be a specialized cortical area whose job it is to integrate the diffuse, distributed neural activity associated with a single act and decide whether it was internally generated or externally imposed.
Writing in the pages of the Journal of Neuroscience, Zarinah Agnew and Richard J. S. Wise report that they’ve found an area of the brain that is a candidate for the job of agency detector, the Parietal Operculum1.
This work pushes the boundaries of research into the nature of free will. One class of phenomena which motivates the free-will-as-post-hoc theory is the so-called automatisms: actions which are internally generated but feel as though they were caused by an outside agent. A well known example of automatism is the Ouija Board, where it is possible – most likely due to suggestion and the ability to ascribe agency directly to the other “players” – to feel as though one is not moving a planchette. Another is automatic writing, a phenomenon in which an individual composes pieces (in some cases entire novels) without any feeling of agency.
That the experience of will can break down in these ways is a very direct indication (along with a host of others) that our understanding of the phenomenon is minimal, at best. Localizing the brain areas responsible for the feeling of free will is one step towards understanding it.
1. Agnew Z, Wise RJ. Separate areas for mirror responses and agency within the parietal operculum. J Neurosci 28: 12268-12273, 2008.