The University of Washington explains that the prefrontal cortex is responsible for activities that include problem solving, processing complex thoughts and causing emotions. The prefrontal cortex is located at the front of the brain, in the outer layer of structure called the cerebral cortex.
According to an article in the journal Brain, scientists still have many questions about the function of the prefrontal cortex. In contrast to people who have sustained damage to the rear lobes of the brain and lose obvious and predictable functions, those with damage to the prefrontal cortex often exhibit puzzling changes. In many patients with lesions in the prefrontal cortex, intellectual ability is not affected. However, such patients often experience serious behavioral changes, and planning and reasoning are often greatly impaired.
According to Wikipedia, the prefrontal cortex carries out the executive functions of the brain. These include determining right from wrong, predicting future outcomes and working towards goals. Additionally, the prefrontal cortex is involved in repressing socially inappropriate behaviors. Research has shown that those who are incarcerated, sociopathic or suffering from mental illness often have reduced prefrontal cortices and lack the number of neural connections in this area that normal people have.
The prefrontal cortex has been very important in the evolution of humans. According to Wikipedia, the human brain has tripled in size over the last 5 million years of evolution. During the same time period, the prefrontal cortex has expanded sixfold in size.