Although classical AI approaches have usually neglected the emotional dimension, it is becoming a key part of many of the current artificial cognitive architectures. The neurobiological study of emotions during the last decades has offered new insight. The analysis of patients that have lost part of their brains, and the use of brain imaging techniques, give scientists many significant clues about how our emotional brain works.
In the book “Descartes’ Error: Emotion, Reason, and the Human Brain” by neurologist Antonio R. Damasio , the argument is made that emotion and reason are quite dependent upon one another. The famous case of Phineas Cage, whose frontal lobes were damaged in an accident, is explored in this book. Phineas P. Gage (1823-1860) suffered a brain injury at work when a tamping iron accidentally passed through his skull (see picture).
Gage’s case is said to be the first clinical proof of the role of the frontal lobe in personality and social interaction. Actually, after Gage suffered the accident, his friends said that he was no longer the same – he became a very unsociable person. The following is an excerpt from Harlow – Cage’s doctor (1968):
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. 
Damasio proposed a theory called somatic marker hypothesis, which suggests a link between the fontal lobes, emotion, and decision making. Since Cage’s case, Antonio Damasio, Marc Hauser and colleagues have studies six more cases with damage in the ventromedial prefrontal cortex (VMPC), one of the social motional nodes of the brain. They have concluded that this damage increases utilitarian moral judgements . Here, the term utilitarian comes form utilitarism, and and refers to moral judgements or dilemmas where there is a conflict between aggregate welfare and highly emotionally aversive behaviors (for instance, having to sacrifice one person’s life to save a number of other lives).
According to Raymond J. Dolan,
Patients with medial prefrontal lesions often display irresponsible behavior, despite being intellectually unimpaired. But similar lesions occurring in early childhood can also prevent the acquisition of factual knowledge about accepted standards of moral behavior. 
 Antonio R. Damasio (1995) Descartes’ Error: Emotion, Reason, and the Human Brain
 Harlow, J.M. (1868). “Recovery from a Passage of an Iron Bar through the Head”. Publications of the Massachusetts Medical Society 2: 327-347.
 Michael Koenigs, Liane Young, Ralph Adolphs, Daniel Tranel, Fiery Cushman, Marc Hauser & Antonio Damasio. Nature 446, 908-911 (19 April 2007).
 Raymond J. Dolan. On the neurology of morals. Nature Neuroscience 2, 927 – 929 (1999).
Phineas Gage information page: http://www.deakin.edu.au/hmnbs/psychology/gagepage/index.php
Fact sheets on brain injury: http://www.braininjury.org.au/portal/index.php