Prefrontal cortex

Anatomy

The prefrontal cortex (PFC) relates to the portion of the brain located on the anteriormost portion of the frontal lobe, occupying portions of all three surfaces of the frontal lobe (orbital, medial and lateral surfaces). It is also called the ‘frontal granular cortex’ and ‘frontal association cortex’.

The prefrontal cortex comprises approximately one-third of the entire cerebral cortex. It is important to mention that this region starts to develop before birth, progresses slowly throughout childhood, and finally completes its development process (myelinization) in late adolescence. This is one of the reasons why children don't have as developed high-order cognitive abilities as adults do. 

In order to better understand the specifics of each part of this large portion of the brain, the neuroscientists decided to divide this region into subregions. There is still not a universal consensus on this division, however, the most commonly used division includes three subregions: 

• Medial region (further divided into dorsomedial and ventromedial regions)
• Lateral region (further divided into dorsolateral and ventrolateral regions) 
• Orbitofrontal region

Connectivity

The prefrontal cortex builds rich subcortical reciprocal connections with the amygdala, hypothalamus, midbrain, and pons. This way the phylogenetically more primitive functions (e.g. autonomic activity, visceral functions, primary emotions) are integrated with high-order brain functions (e.g. thinking, calculating, motivation, etc). 

Understandably, each region has its own unique connections and consequently its own specific functions: 

• The medial region of the prefrontal cortex builds reciprocal connections with brain regions that are implicated in emotional processing (amygdala), memory (hippocampus) and higher-order sensory regions (within the temporal cortex).
• The lateral region is primarily connected to the brain regions that are implicated in motor control (basal ganglia, premotor cortex, supplementary motor area), thalamus, performance monitoring (cingulate cortex) and higher-order sensory processing (within the neocortex).

The orbitofrontal region mainly forms neural connections with the brain regions involved in emotional regulation such as the amygdala, the medial portion of the thalamus, the hypothalamus and the basal ganglia (ventromedial portion of the caudate nucleus).

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Blood supply and venous drainage 

The prefrontal cortex receives a rich blood supply via the anterior cerebral artery and middle cerebral artery (branches of the internal carotid artery).

The anterior and lateral portions of the prefrontal cortex are mainly vascularized by the middle cerebral artery, while the superior and medial aspects are supplied by the anterior cerebral artery.

The venous blood from the prefrontal cortex is drained into the superior sagittal sinus and inferior sagittal sinus via the superficial cerebral veins.

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Functions

The division of the prefrontal cortex into three different subregions is mainly due to their unique connections to other parts of the brain and their different functions. 

The medial prefrontal region participates in the processes such as motivation, spatial memory, bimanual coordination, self-initiated movements and focus. It serves as the "inspiration area", which is why injuries of this region can lead to apathy and loss of concentration. Additionally, some studies indicate that the portion of this region (cingulate cortex) is involved in the perception of pain, while the ventromedial region is involved in decision making and memory. 

The lateral prefrontal region provides the cognitive foundation for different patterns of behavior, orientation and reasoning. In addition, this region also helps in planning, the general and temporal organization of activities (e.g. daily routines), and switching from one task to another. The injuries of this region can lead to the inability to organize multiple activities in a meaningful order, to switch between the activities, and as well to adapt to rule changes. Due to its close proximity to the primary cortical center for vocalization and language production (Broca's area) this region is involved in the abstract mediation of the verbal expression of language.

The orbital prefrontal region is the region that participates in impulse control, emotional processing, and social cognition. Because of its rich connections with the hypothalamus, the orbital region mediates reward aspects of eating and self-regulation. Additionally, it is able to ignore distractions and help in maintaining attention on a certain task. The injuries of this region lead to the exact same symptoms that famous neurological patient Phineas Gage had (see above).