The control of human emotion differs from that of many species because of the presence of the massive cerebral hemispheres, which act, in part, to regulate the functions of many lower brain systems (Damasio, 1985). The importance of the cerebral hemispheres for emotion and personality, in particular the frontal lobes, was made strikingly clear over a century ago by the case of Phineas Gage.
Gage, 25, was a construction foreman who in 1848 had the following 'bad day on the job'. Working on railroad construction, Gage was blasting a path through hard rock. His co-workers could not know that they were about to witness one of the most celebrated incidents in the annals of neuroscience. Following procedures in which he was skilled, Gage drilled a hole in the ground, filled it with explosive powder, and inserted an iron rod. Next, a fuse was lit. Though Gage was an expert at this, on this occasion he was distracted and the charge blew up in his face. The explosion blew the 13-pound, 3 feet long iron rod through his left cheek, the base of his skull, and the front of his brain. It largely destroyed a part of Gage's frontal cortex. The rod then exited through the top of his head, landing 80 feet away smeared in blood and brain.
With a little assistance Gage walked to a cart that brought him the short 1km trip to his local lodgings. The first physician to see him was Dr Edward H. Williams:
I first noticed the wound upon the head before I alighted from my carriage, the pulsations of the brain being very distinct. Mr Gage, during the time I was examining this wound, was relating the manner in which he was injured to the bystanders. I did not believe Mr Gage's statement at that time, but thought he was deceived. Mr Gage persisted in saying that the bar went through his head .... Mr G. got up and vomited; the effort of vomiting pressed out about half a teacupful of the brain, which fell upon the floor.
Dr J. M. Harlow, who also treated Gage, described the incident:
The patient was thrown upon his back by the explosion, and gave a few convulsive motions of the extremities, but spoke in a few minutes. He seemed perfectly conscious, but was becoming exhausted from the haemorrhage. Pulse 60, and regular. His person, and the bed on which he was laid, were literally one gore of blood . . . the blood pouring from the top of his head . . . You will excuse me for remarking here, that the picture presented was, to one unaccustomed to military surgery, truly terrific. He bore his sufferings with firmness, and directed my attention to the hole in his cheek, saying, 'the iron entered here and passed through my head' (1868).
Miraculously, he survived the injury. He was able to walk and speak. Further, he could describe what happened in full detail and communicate in a rational way. Yet Gage had changed deeply. Before the accident, Gage was a model citizen and employee, but the frontal lobe damage transformed his very character. As related by the eminent neurologist Antonio Damasio (1994):
''Gage's disposition, his likes and dislikes, his dreams and aspirations are all to change. Gage's body may be alive and well, but there is a new spirit animating it''.
Once serious, industrious, energetic, and responsible, immediately after the accident Gage became irresponsible, thoughtless of others, lacking in planfulness, and indifferent to the consequences of his actions. Gage's physician described the change as follows:
''His physical health is good, and I am inclined to say that he has recovered. Has no pain in his head, but says it has a queer feeling that he is not able to describe. . . His contractors, who regarded him as the most efficient and capable of foreman in their employ previous to his injury, considered the change in his mind so marked that they could not give him his place again. The equilibrium or balance, so to speak, between his intellectual faculty and animal propensities, seems to have been destroyed. He is 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 operation, which are no sooner arranged that they are abandoned in turn for others. . . . His mind was radically changed, so decidedly that his friends and acquaintances said that he was ''no longer Gage''. (Harlow, 1868).
Gage's story is dramatic to say the least. But it suggests that there exists deep interconnections between brain functioning and personality functioning, that brain and personality are intimately, directly connected. Similar cases, although less spectacular, continue to be reported. They occur following extensive frontal lobe surgery. Such patients usually remain well-orientated, alert, with memory intact. Intellectual capacity seems undiminished, at least on the surface. However, as with Gage, there is a loss of sustained attention. The ability to plan and order daily activities is also markedly reduced.
With respect to emotion, there are also marked changes. Often the patient seems to cease to experience strong emotion. Feelings become transitory and superficial.
Significant brain injury is often fatal but sometimes scientists learn a lot from accidents. Physical damage to Gage's brain changed his thinking and behaviour so radically that he became, psychologically, a different person. The conclusion to be drawn from the history of an unfortunate human experience emphasizes the importance of the frontal lobes for personality and for the control and expression of human emotions.
