The will of the brain: cerebral correlates of willful acts.

Current imaging techniques can depict physiological events in the brain which accompany sensory perception and motor activity, as well as cognition and speech. "Pure" mental events unaccompanied by sensory input or motor/behavioral output also induces cerebral functional changes which apparently are related to inner representations of thoughts, ideas, visions, inner speech and so forth. Cerebral events during cognition, mental effort, imagined volitional acts, augment the activity in the prefrontal cortex. An augmentation in the cerebellum is also recorded. It is known that temporally organized (sequential) neuronal activity takes place in these structures. The prefrontal activation accompanying volitional acts most likely corresponds to a willful mobilization of inner representations of future events. These representations serve as action programs for the achievement of the goal. Phylogenetically older parts of the cerebral cortex close to the midline (the cingulate gyrus) participate in willful acts. They are possibly involved in emotional/motivational ("value") aspects of volition. Abnormal volition ("sick will") is encountered in organic dementia, Parkinson's disease, depression, and schizophrenia. Such disorders are characterized by inactivity, lack of ambitions, and a reduced motor and verbal output. Patients in these groups often show a decreased activity in prefrontal regions. Individuals with supraorbital and mesial frontal lesions may develop a so-called psychopathic behavior including abnormalities of volition with lack of impulse control, boredom susceptibility, sensation-seeking behavior, and abnormal risk taking. Knowledge about cerebral events coupled to willful acts may shed some light on the "collective will" expressed by groups of individuals and organizations.