The functional deficits that result from damage to the human frontal lobe are diverse and devastating, particularly if both hemispheres are involved. This broad range of clinical effects stems from the fact that the frontal cortex has a wider repertoire of functions than any other neocortical region (consistent with the fact that the frontal lobe in humans and other primates is the largest of the brain's lobes and comprises a greater number of cytoarchitectonic areas). The particularly devastating nature of the behavioral deficits after frontal lobe damage reflects the role of this part of the brain in maintaining what is normally thought of as an individual's “personality.” The frontal cortex integrates complex perceptual information from sensory and motor cortices, as well as from the parietal and temporal association cortices. The result is an appreciation of self in relation to the world that allows behaviors to be planned and executed normally. When this ability is compromised, the afflicted individual often has difficulty carrying out complex behaviors that are appropriate to the circumstances. These deficiencies in the normal ability to match ongoing behavior to present or future demands are, not surprisingly, interpreted as a change in the patient's “character.”

The case that first called attention to the consequences of frontal lobe damage was Phineas Gage, a worker on the Rutland and Burlington Railroad in mid-nineteenth-century Vermont. A conventional way of blasting a rock in that era was to tamp powder into a hole with a heavy metal rod. Gage, the popular and respected foreman of the crew, was undertaking this procedure one day in 1848 when his tamping rod sparked the powder, setting off an explosion that drove the rod, which was about a meter long and 4 or 5 centimeters in diameter, through his left orbit (eye socket), destroying much of the frontal part of his brain in the process (see the illustration on the page introducing this Unit). Gage, who never lost consciousness, was promptly taken to a local doctor, who treated his wound. An infection set in, presumably destroying additional frontal lobe tissue, and Gage was an invalid for several months. Eventually, he recovered and was—to outward appearances—well again. Those who knew Gage, however, were profoundly aware that he was not the “same” individual that he had been before. A temperate, hardworking, and altogether decent person had, by virtue of this accident, been turned into an inconsiderate, intemperate lout who could no longer cope with normal social intercourse or the kind of practical planning that had allowed Gage the social and economic success he enjoyed before.

The physician who had looked after Gage until his death in 1863 summarized his impressions of Gage's personality as follows:

[Gage was] fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operations, which are no sooner arranged than they are abandoned in turn for others appearing more feasible. A child in his intellectual capacity and manifestations, he has the animal passions of a strong man. Previous to his injury, although untrained in the schools, he possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smart businessman, very energetic and persistent in executing all his plans of operation. In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was ‘no longer Gage’.

J. M. Harlow, 1868 (Publications of the Massachusetts Medical Society 2: pp. 339–340)

Another classical case of frontal lobe deficits was a patient followed for many years by the neurologist R. M. Brickner during the 1920s and '30s. Joe A., as Brickner referred to his patient, was a stockbroker who underwent bilateral frontal lobe resection because of a large tumor at age 39. After the operation, Joe A. had no obvious sensory or motor deficits; he could speak and understand verbal communication and was aware of people, objects, and temporal order in his environment. He acknowledged his illness and retained a high degree of intellectual power, as judged from an ongoing ability to play an expert game of checkers. Nonetheless, Joe A.'s personality had undergone a dramatic change. A restrained, modest man, he became boastful of professional, physical, and sexual prowess, showed little restraint in conversation, and was unable to match the appropriateness of what he said to his audience. Like Gage, his ability to plan for the future was largely lost, as was much of his earlier initiative and creativity. Even though he retained the ability to learn complex procedures, he was unable to return to work and had to rely on his family for support and care.

Sadly, these effects of damage to the frontal lobes have also been documented by the many thousands of frontal lobotomies (or “leukotomies”) performed in the 1930s and '40s as a means of treating mental illness. The rise and fall of this “psychosurgery” provides a compelling example of the frailty of human judgment in medical practice, and of the conflicting approaches of neurologists, neurosurgeons, and psychiatrists in that era to the treatment of mental disease (Box B).

Box B

Psychosurgery.