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Prefrontal cortex

In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. It is the association cortex in the frontal lobe.[2] The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA46, and BA47.[1]

This brain region is involved in a wide range of higher-order cognitive functions, including speech formation (Broca's area), gaze (frontal eye fields), working memory (dorsolateral prefrontal cortex), and risk processing (e.g. ventromedial prefrontal cortex). The basic activity of this brain region is considered to be orchestration of thoughts and actions in accordance with internal goals.[3] Many authors have indicated an integral link between a person's will to live, personality, and the functions of the prefrontal cortex.[4]


This brain region has been implicated in executive functions, such as planning, decision making, working memory, personality expression, moderating social behavior and controlling certain aspects of speech and language.[5][6][7][8] 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).


The frontal cortex supports concrete rule learning, with more anterior regions supporting rule learning at higher levels of abstraction.[9]

as the granular frontal cortex

as the projection zone of the of the thalamus

medial dorsal nucleus

as that part of the frontal cortex whose electrical stimulation does not evoke movements

Function[edit]

Executive function[edit]

The original studies of Fuster and of Goldman-Rakic emphasized the fundamental ability of the prefrontal cortex to represent information not currently in the environment, and the central role of this function in creating the "mental sketch pad". Goldman-Rakic spoke of how this representational knowledge was used to intelligently guide thought, action, and emotion, including the inhibition of inappropriate thoughts, distractions, actions, and feelings.[29] In this way, working memory can be seen as fundamental to attention and behavioral inhibition. Fuster speaks of how this prefrontal ability allows the wedding of past to future, allowing both cross-temporal and cross-modal associations in the creation of goal-directed, perception-action cycles.[30] This ability to represent underlies all other higher executive functions.


Shimamura proposed Dynamic Filtering Theory to describe the role of the prefrontal cortex in executive functions. The prefrontal cortex is presumed to act as a high-level gating or filtering mechanism that enhances goal-directed activations and inhibits irrelevant activations. This filtering mechanism enables executive control at various levels of processing, including selecting, maintaining, updating, and rerouting activations. It has also been used to explain emotional regulation.[31]


Miller and Cohen proposed an Integrative Theory of Prefrontal Cortex Function, that arises from the original work of Goldman-Rakic and Fuster. The two theorize that "cognitive control stems from the active maintenance of patterns of activity in the prefrontal cortex that represents goals and means to achieve them. They provide bias signals to other brain structures whose net effect is to guide the flow of activity along neural pathways that establish the proper mappings between inputs, internal states, and outputs needed to perform a given task".[32] In essence, the two theorize that the prefrontal cortex guides the inputs and connections, which allows for cognitive control of our actions.


The prefrontal cortex is of significant importance when top-down processing is needed. Top-down processing by definition is when behavior is guided by internal states or intentions. According to the two, "The PFC is critical in situations when the mappings between sensory inputs, thoughts, and actions either are weakly established relative to other existing ones or are rapidly changing".[32] An example of this can be portrayed in the Wisconsin Card Sorting Test (WCST). Subjects engaging in this task are instructed to sort cards according to the shape, color, or number of symbols appearing on them. The thought is that any given card can be associated with a number of actions and no single stimulus-response mapping will work. Human subjects with PFC damage are able to sort the card in the initial simple tasks, but unable to do so as the rules of classification change.


Miller and Cohen conclude that the implications of their theory can explain how much of a role the PFC has in guiding control of cognitive actions. In the researchers' own words, they claim that, "depending on their target of influence, representations in the PFC can function variously as attentional templates, rules, or goals by providing top-down bias signals to other parts of the brain that guide the flow of activity along the pathways needed to perform a task".[32]


Experimental data indicate a role for the prefrontal cortex in mediating normal sleep physiology, dreaming and sleep-deprivation phenomena.[33]


When analyzing and thinking about attributes of other individuals, the medial prefrontal cortex is activated, however, it is not activated when contemplating the characteristics of inanimate objects.[34]


Studies using fMRI have shown that the medial prefrontal cortex (mPFC), specifically the anterior medial prefrontal cortex (amPFC), may modulate mimicry behavior. Neuroscientists are suggesting that social priming influences activity and processing in the amPFC, and that this area of the prefrontal cortex modulates mimicry responses and behavior.[35]


As of recent, researchers have used neuroimaging techniques to find that along with the basal ganglia, the prefrontal cortex is involved with learning exemplars, which is part of the exemplar theory, one of the three main ways our mind categorizes things. The exemplar theory states that we categorize judgements by comparing it to a similar past experience within our stored memories.[36]


A 2014 meta-analysis by Professor Nicole P.Yuan from the University of Arizona found that larger prefrontal cortex volume and greater PFC cortical thickness were associated with better executive performance.[37]

Animation, prefrontal cortex of left cerebral hemisphere (shown in red)

Animation, prefrontal cortex of left cerebral hemisphere (shown in red)

Front view

Front view

Lateral view

Lateral view

Medial perspective

Medial perspective

Lobotomy

Interference theory

Self-model theory of subjectivity

Dorsomedial prefrontal cortex

Ventromedial prefrontal cortex

Diagram (ua.edu)

Diagram (universe-review.ca)

at the BrainMaps project

Stained brain slice images which include the "Prefrontal cortex"