Prefrontal cortex

The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas. In terms of its cytoarchitectonics, the prefrontal cortex is defined by the presence of an internal granular layer IV (in contrast to the agranular premotor cortex). The prefrontal cortex can be divided in several ways, one of which is into three basic areas:

• The orbitofrontal (OFC) and ventromedial areas (vm-PFC);
• the dorsolateral prefrontal cortex (dl-PFC);
• the anterior and ventral cingulate cortex.^[1]
  

Other areas that can be distinguished are the ventrolateral cortex (vl-PFC), the medial prefrontal cortex (m-PFC), and the anterior prefrontal cortex (a-PFC).

This brain region has been implicated in planning complex cognitive behaviors, personality expression, and moderating correct social behavior. The basic activity of this brain region is considered to be orchestration of thoughts and actions in accordance with internal goals.

The most typical neurologic term for functions carried out by the pre-frontal cortex area is Executive Function. Executive Function relates to abilities to differentiate among conflicting thoughts, determine good and bad, better and best, same and different, future consequences of current activities, working toward a defined goal, prediction of outcomes, expectation based on actions, and social "control" (the ability to suppress urges that, if not suppressed, could lead to socially-unacceptable outcomes).

Many authors have indicated an integral link between a person's personality and the functions of the prefrontal cortex.

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Brain linkages

The prefrontal cortex has a high number of interconnections between both the brainstem's Reticular Activating System (RAS) and the limbic system. As a result, the centers in the prefrontal cortex depend significantly on high levels of alertness, and emotional linkages with deeper brain structures related to control of pleasure, pain, anger, rage, panic, aggression (fight-flight-freeze responses), and basic sexual responses.

Studies

The classic case of earlier studies of prefrontal cortex function involved a railroad construction supervisor, Phineas Gage, who, in 1848, had a metal rod pierce his left cheek and exit the top of his head. After the event, he had normal memory and abilities to walk and talk, but, because of the injury to the prefrontal cortex, his personality and work ability completely changed. Friends described him as a completely new person and whereas he previously was able to begin and complete work-based goals, after the injury he was unable to complete the multiple tasks that he started. He was described as more irritable, quick tempered, and impatient- all characteristics that he previously did not exhibit.^[2]

Subsequent studies, on patients with prefrontal injuries, have shown that the patients verbalized what the most appropriate social responses would be under certain circumstances, yet, when actually performing, they instead pursued behavior that is aimed at immediate gratification despite knowing the longer-term results would be self-defeating.

The interpretation of this data indicates that not only are skills of comparison and understanding of eventual outcomes harbored in the prefrontal cortex but the prefrontal cortex (when functioning correctly) controls the mental option to delay immediate gratification for a better or more rewarding longer-term gratification result. This ability to wait for a reward is one of the key pieces that define optimal executive function of the human brain.

Other disorders

In the last few decades, brain imaging systems have been used to determine brain region volumes and nerve linkages. Several studies have indicated that reduced volume and interconnections of the frontal lobes with other brain regions is common in those with depression, people subjected to repeated stressors,^[3] suicide victims,^[4] incarcerated criminals, sociopaths, and drug addicts. It is felt that at least some of the human abilities to feel guilt or remorse, and to interpret reality, lie in the prefrontal cortex.^{[citation needed]}

References

1. ^ http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=pubmed&dopt=AbstractPlus&list_uids=12479840
2. ^ Antonio Damasio, Descartes' Error. Penguin Putman Pub., 1994
3. ^ Liston C et al (2006). "Stress-induced alterations in prefrontal cortical dendritic morphology predict selective impairments in perceptual attentional set-shifting". J Neurosci 26 (30): 7870-4. PMID 16870732.
4. ^ Rajkowska G. "Morphometric methods for studying the prefrontal cortex in suicide victims and psychiatric patients". Ann N Y Acad Sci 836: 253-68. PMID 9616803.

• Richard M. Burton, The Anatomy, Chemistry and Genetics of Human Behavior, Newport. 1996.

• Miller EK, Cohen JD (2001). "An integrative theory of prefrontal cortex function". Annu Rev Neurosci 24: 167-202. PMID 11283309.

• Lebedev M et al (2004). "Representation of attended versus remembered locations in prefrontal cortex". PLoS Biology 2 (11): e365. PMID 15510225.

• Fuster JM (1997) The Prefrontal Cortex: Anatomy, physiology, and neuropsychology of the frontal lobe, 2 Edition: Lippincott, Williams & Wilkins.

See also

• Attention versus memory in prefrontal cortex