Human voluntary action: from thought to movement

The ability to decide and act autonomously is a distinctive feature of human cognition. From a motor neurophysiology viewpoint, these 'voluntary' actions can be distinguished by the lack of an obvious triggering sensory stimulus: the action is considered to be a product of thought, rather than a reflex result of a specific input. A reverse engineering approach shows that such actions are caused by neurons of the primary cortex, which in turn depend on medial frontal areas, and finally a combination of prefrontal cortical connections and subcortical drive from basal ganglia loops. One traditional marker of voluntary action is the EEG readiness potential (RP), recorded over the frontal cortex prior to voluntary actions. However, the interpretation of this signal remains controversial, and very few experimental studies have attempted to link the RP to the thought process that lead to voluntary action. In this talk, I will report new studies that show learning an internal model about the optimum delay at which to act influences the amplitude of the RP. More generally, a scientific understanding of voluntariness and autonomy will require new neurocognitive paradigms connecting thought and action.