On volition: a neurophysiologically oriented essay

During the last decades, the enigmatic field of volition has been the object of quantitative brain mapping studies. In this essay, emphasis will be given to brain mapping observations during overt or imagined willed acts in conscious normal individuals. The findings suggest that such acts are ‘formulated’ in the frontal/prefrontal cortex as neuronal programs for future motor, behavioural, verbal, or cognitive acts. During imagined movements or speech, brain mapping reveals important prefrontal activations which contrast to perirolandic activations during overt willed acts. In psychiatric disorders with symptoms of a ‘sick will', like in schizophrenia, affective disorders, and organic dementia, reductions of the resting prefrontal activity have been recorded. The relationship between will and prefrontal activity is compatible with the view that frontal/prefrontal (efferent) parts of the cortex are involved in the serial temporal programming of motor behaviour, speech, and cognition. In addition, there are unconscious mechanisms participating in volition. Electrophysiological evidence presented by Libet (1985 et seq.) supports this view.