Human Neuropsychology

Publisher Summary This chapter deals with neuropsychological effects of prefrontal damage in humans. The main sources of empirical data on the effects of prefrontal damage in the human are diseases and traumatic lesions of the frontal lobe, and cases of frontal psychosurgery. The neuropsychological effects of prefrontal damage vary greatly depending on the location and the extent of that damage. Apathy and general disinterest are common results of a large prefrontal lesion, especial if it involves lateral or medial cortex. Depression is the most common affective disorder from more circumscribed prefrontal lesions, especially if they involve the left lateral and polar cortex, although some affective disorders can result from orbital damage as well. Orbital lesions are accompanied by hyperreactivity to extraneous or irrelevant stimuli, yet low reactivity to emotional stimuli. They also lead to the weakening of autonomic or visceral signals that are concomitant to normal emotion. All prefrontal lesions, by reason of the emotional and cognitive changes they produce, tend to affect adversely the social life of the patient, usually constricting it. Orbital lesions, however, generally induce the most dramatic changes in social behavior, and these changes are usually opposite to social restraint. In the cognitive sphere, disorders of attention are the most common disorders of executive function caused by prefrontal damage. Those abnormalities of the control of attention may take several forms: loss of general alertness, sensory neglect, excessive distractibility, set-shifting disorder, disorder of ocular control, difficulty in sustaining attention, internal interference, and faulty executive set (executive attention).