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|Brain: Dorsolateral Prefrontal Cortex|
|Latin||Cortex praefrontalis dorsolateralis|
|Brain: Dorsolateral Prefrontal Cortex|
|Latin||Cortex praefrontalis dorsolateralis|
The Dorsolateral Prefrontal Cortex (DLPFC or DL-PFC) is an area in the anterior region of the primate brain. DL-PFC is believed to exist starting at the Brodmann Area 10 to 8. Dorsolateral Prefrontal Cortex (DL-PFC) is one of the most evolved parts of the human brain and undergoes an extremely prolonged period of maturation until adulthood. The human brain can be classified into two regions: Cerebral Cortex, the outermost layer of the brain, and Subcortical Layers that are buried deep inside. DL-PFC is a subcortical region in the brain. Dorsolateral Prefrontal Cortex falls in the region called Prefrontal Cortex. The Prefrontal Cortex contains neurons that are responsible for registering the sensory cue, in holding it "on line," and in releasing the motor responses in the course of task performance. The collections of selective cells form Dorsolateral Prefrontal Cortex. DLPFC is connected to the Orbitofrontal Cortex, and to a variety of brain areas, which include the Thalamus, parts of the Basal Ganglia (specifically, the dorsal Caudate Nucleus), the Hippocampus, and primary and secondary association areas of Neocortex, including posterior temporal, parietal, and occipital areas. Also, Dorsolateral Prefrontal Cortex is the end point for the Dorsal Pathway (Stream) that tells the brain how to interact with the stimuli. Ventrolateral Prefrontal Cortex, on the other hand, is the end point of the Ventral Pathway (Stream) that brings information about the stimuli’s characteristics.
The formation of Dorsolateral Prefrontal Cortex by clustering of spatial selective neurons gives it a neural circuitry that encompasses the entire range of sub-functions necessary to carry out an integrated response: sensory input, retention in short-term memory, and motor signaling. Historically Dorsolateral Prefrontal cortex is defined by its connection to: superior temporal cortex, posterior parietal cortex, anterior and posterior cingulate, premotor cortex, retrosplenial cortex, and Neocerebellum. These vast connections to other parts of the brains allows DLPFC to regulate the activity of those regions and as well receive information from, and be regulated by these regions. Dorsolateral Prefrontal Cortex is primarily known for its involvement in the A-not-B or delayed response task because this task requires holding the information in mind (working memory). Scientists believe that DLPFC is also involved in the storage of working memory. In a research involving study of A-not-B task with adult macaques, it was concluded that lesions that destroy DLPFC disrupt the macaques’ performance of the task. However, lesions to other brain parts didn’t impair the performance of the A-not-B task.
Dorsolateral Prefrontal Cortex is, however, not required for the memory of a single item; thus, recognition memory is unimpaired even after damage to the Dorsolateral Prefrontal Cortex. However, if two items must be compared in the memory then involvement of Dorsolateral Pre-Frontal Cortex is required. For example, people with damaged dorsolateral prefrontal cortex were not able to identify a picture they had seen after sometime when given to choose from two pictures. Moreover, these subjects also fail in Wisconsin Card-Sorting Test because these patients loose track of the currently correct rule and persistently organize their cards in the previously correct rule Dorsolateral Prefrontal Cortex is not active when one is asleep as it is a part that deals with waking thought and reality testing.
More specifically, the DLPFC is most frequently related to the dysfunction of drive, attention and motivation. Patients with minor DLPFC damage display disinterest in their surroundings and are deprived of spontaneity in language as well as behavior. Patients may also be less alert than normal to people and events they know. Damage to this region in a person also leads to the lack of motivation to do things for themselves and/or for others.
DLPFC is involved in both risky and moral decision making; for example, when individuals are faced with moral decisions like how to distribute limited resource, DLPFC is activated. This region is also active when costs and benefits of alternative choices are of interests. Similarly, when options for choosing alternatives is present, DLPFC evokes preference towards most equitable option and suppresses temptation to maximizing personal gain.
The Right DLPFC in conjunction with temporo-parietal junction establishes the capacity for individuals to adopt the perspective of someone else. This facilitates cooperation and correspondence. A study conducted to monitor activation of Dorsolateral Prefrontal Cortex through administration of a trust game concluded that activation of the right dorsolateral prefrontal cortex may represent the attempt to suppress selfish behavior and consider the possibility of acting cooperatively. In contrast, activation of the left temporo-parietal junction in left DLPFC may represent one's attempts to infer the intentions of other people. Furthermore, it was discovered that activation of the anterior medial prefrontal cortex elevated, especially in younger adolescents, when they decided to act selfishly and not correspond.
The DLPFC is a major factor in controlling functions such as attention, executive function, and working memory. Working Memory is an ability that humans and primates have that allows more information to be held as well as coherent thoughts and ideas, making it be called the “mental sketch-pad” or a “on-line memory”.  However, WM has a capacity limit that can cause hypofrontality, or a reduction in the activity of the PFC, in people who are healthy or with DLPFC dysfunctions, such as those with schizophrenia.Working Memory is dependent upon the functionality of the DLPFC as reduced activity in the area correlates to poor performance on working memory tasks.  The cognitive functions of working memory is prominent in other areas of the brain as well, not limited to just the DLPFC.
The DLPFC may also be involved in the act of deception and lying, which is thought to inhibit normal tendency to truth telling. Research also suggests that using TMS on the DLPFC can impede a person's ability to lie or to tell the truth. Using MRIs "Lie was discriminated from truth on a single-event level with an accuracy of 78%." More recent research has found a connection between the DLPFC and lucid dream states in which executive function is retained. Additionally, supporting evidence suggests that the DLPFC may also play a role in conflict-induced behavioral adjustment. To find the correlation between the two, several tests have helped researchers see important connections. One way in which this has been tested is through the Stroop test. In this experiment, subjects are shown a name of a color printed in colored ink and then are asked to name the color of the ink as fast as possible. Conflict arises when the color of the ink does not match the name of the color printed. During this experiment, researchers tracked subjects’ brain activity and found that noticeable activity occurs within the DLPFC. The activation of the DLPFC correlated with the behavioral performance suggests that this region maintains the high demands of the task to resolve conflict and in theory plays a role in taking control.
In further studies, DLPFC activity indicated that human intelligence may be associated with this region. To investigate this hypothesis, researchers took a closer look at patients with DLPFC damage and administered the Wechsler Adult Intelligence Scale (WAIS) to assess this area’s necessity for performance. The WAIS, more specifically, was used as a way to examine the DLPFC’s function for general intelligence. In doing so, studies showed that patients with DLPFC damage in comparison to healthy patients did consistently worse in tasks requiring working memory and processing speed. It’s important to take note that studies like these have found a correlation between the DLPFC and human intelligence, but do not claim that all human intelligence is a function of the DLPFC. In other words, this region may be attributed to general intelligence on a broader scale as well as very specific roles, but not all roles. For example, using imaging studies like PET and fMRI indicate DLPFC involvement in deductive, syllogistic reasoning. Specifically, when involved in activities that require syllogistic reasoning, left DLPFC areas are especially and consistently active.
The DLPFC may also be involved in threat-induced anxiety. In one experiment, participants were asked to rate themselves as behaviorally inhibited or not. Those who rated themselves as behaviorally inhibited, moreover, showed greater tonic (resting) activity in the right-posterior DLPFC. Such activity is able to be seen through Electroencephalogram (EEG) recordings. Individuals who are behaviorally inhibited are more likely to experience feelings of stress and anxiety when faced with a particularly threatening situation. In one theory, anxiety susceptibility may increase as a result of present vigilance. Evidence for this theory includes neuroimaging studies that demonstrate DLPFC activity when an individual experiences vigilance. More specifically, it is theorized that threat-induced anxiety may also be connected to deficits in resolving problems, which leads to uncertainty. When an individual experiences uncertainty, there is increased activity in the DLPFC. In other words, such activity can be traced back to threat-induced anxiety.
As DL-PFC goes under the long maturational changes, one change that has been attributed to DL-PFC for making early cognitive advances is the increasing level of neurotransmitter Dopamine in DL-PFC. When the receptors of neurotransmitter Dopamine were blocked, it was seen that the adult macaques had deficit in the delayed response task, as if the whole DFPLC was taken out altogether. Similar situation was seen when the macaques were injected with MPTP injection that reduces the level of Dopamine in the dorsolateral prefrontal cortex. Even though, there have been no physiological studies about involvement of Cholinergic Actions in sub-cortical areas, behavioral studies indicate that neurotransmitter Acetylcholine is essential for working memory function of the DLPFC.
Schizophrenia may be partially attributed to a lack in activity in the frontal lobe Especially, Dorsolateral prefrontal cortex is hypoactive when a person suffers from Chorionic Schizophrenia. Schizophrenia is also related to lack of Dopamine neurotransmitter in the frontal lobe. The DLPFC dysfunctions are unique among the schizophrenia patients as patients that are diagnosed with depression do not tend to have the same abnormal activation in the DLPFC during working-memory related tasks. Working Memory is dependent upon the DLPFC’S stability and functionally, thus reduced activation of it causes for schizophrenic patients to perform poorly on tasks involving working memory. The poor performance contributes to the added capacity limitations in working memory that is greater than the limits on normal patients. The cognitive processes that deal heavily with the DPLFC, such as memory, attention, and higher order processing, are the functions that once distorted contribute to the factors of the illness.
Research suggests that the DLPFC is greatly impaired when an individual is exposed to acute stress. Specifically, acute stress negatively affects higher-order cognitive function such as working memory (WM). In an experiment, researchers used functional magnetic resonance imaging (fMRI) to record neural activity of healthy participants who were required to finish tasks while being in a stress induced environment. When stress was successfully induced, participant’s neural activity showed reduced working memory related activity in the DLPFC. These finding not only demonstrate the important role of the DLPFC region in relation to stress, but they also suggest that it may play a role in other psychiatric disorders. In patients with post-traumatic stress disorder (PTSD), for example, daily sessions of right dorsolateral prefrontal repetitive transcranial magnetic stimulation (rTMS) at a frequency of 10 Hz resulted in greater therapeutic effects than slower of fake stimulation.
Damage to anterior and mid sections of the DLPFC might impede commitment in a relationship due to impaired self-efficacy.