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The medial prefrontal cortex is the large anterior or frontal lobes of the human brain that seems to be the center of higher cognitive functions. Functional magnetic resonance imaging (fMRI) examinations of activity in these parts of the brain suggest that they are the center of processing of social information and memory functions related to the past, and the making of long-term decisions for the future. While still inconclusive as of 2011, aspects of human activity such as social control in public places, an innate understanding of contemporary morals or values, and goal planning seem to stimulate this region of the brain more than any other.
The front hemisphere of the brain has at its center the medial prefrontal cortex, and neuroimaging research has found that this region of the brain is most strongly linked to what is called self-referential memory. Self-referential memory is memory formation about what type of person someone believes themselves to be, whether they consider themselves honest, smart, having a good sense of humor, and other such assumptions. Processing activity in this region of the brain appears to be dominated by such higher level social functions. Any activity that involves self-referential behavior, or behavior tied to close friends or family, appears to be more thoroughly and permanently encoded in the brain, specifically in the medial prefrontal cortex area.
Activity or social interaction with close friends is known to stimulate a response in the medial prefrontal cortex more than social activity with strangers does. Research in this arena has led to the conclusion that this part of the brain is being used to evaluate other people during these encounters. Brain activity is stronger where there are emotional bonds, regardless of similarities in interests. Even if a stranger has many similar interests as compared to a friend, encounters with the friend will still stimulate the medial prefrontal cortex to a greater degree.
The results of this research have come as a surprise. Prior sociological assumptions were that people identify more with others who have similar beliefs and lifestyles and interests. This now appears to be peripheral, however, and, instead, medial prefrontal cortex brain response gives priority to emotional bonds regardless of differences in behavior between individuals.
While other regions of the brain undergo physical and functional changes as a person ages, the medial prefrontal cortex appears to remain the same. Where evidence of it shrinking in size exists, this seems to directly contribute to impaired memory. The medial prefrontal cortex may actually enlarge in volume with age, as the inferior prefrontal cortex region below it shrinks. Studies that compared young versus old responses that affect the medial prefrontal cortex showed no natural decline with age, which reflects the fact that this region of the brain itself seems more resistant to age-related decline than other parts of the brain are.