The Anterior Cingulate Cortex, Akinetic Mutism, and Human Volition

The anterior cingulate cortex (ACC) has been identified as part of a supervisory attentional network for selecting alternative motor programs in response to top-down cortical processing, particularly in situations involving conflicting cognitive tasks. Bilateral lesions to the ACC may be causally associated with akinetic mutism, where patients are unable to voluntarily initiate responses. The clinical and neuroanatomical evidence for this presumed causal association is examined at length. However, given the many reciprocal projections between cerebral, motor, limbic and paralimbic structures within the executive supervisory network, the association of voluntary behavior with a particular structure (the ACC) is highly controversial and therefore premature at this time. Also considered is the claim that our subjective sense of voluntary control and free will is simply due to our not having conscious access to the underlying neural computations that precede our decisions and actions. On the contrary, the distinction between voluntary and involuntary thoughts and actions may rather be a matter of temporal and directional lag between parallel computations in different neural areas. Finally, with reference to Dennett, there is an extended discussion of whether patients with akinetic mutism are (i) conscious automata, (ii)non-intentional systems, and (iii) in a zombie-like state. The relevance of (i)-(iii) for the cognitive neuroscientific literature is then briefly addressed.