Dorsolateral Prefrontal Cortex
editPrimary Functions
editMore specifically, the DLPFC is most frequently related to the dysfunction of drive, attention and motivation[1]. Patients with minor DLPFC damage display disinterest in their surroundings and are deprived of spontaneity in language as well as behavior[1]. Patients may also be less alert than normal to people and events they know[1]. Damage to this region in a person also leads to the lack of motivation to do things for themselves and/or for others[1].
Secondary Functions
editAdditionally, supporting evidence suggests that the DLPFC may also play a role in conflict-induced behavioral adjustment[2]. 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[3]. 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[4]. 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[5].
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 Weshler Adult Intelligence Scale (WAIS) to assess this area’s necessity for performance[6]. 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[7]. 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[8]. Specifically, when involved in activities that require syllogistic reasoning, left DLPFC areas are especially and consistently active[9].
The DLPFC may also be involved in threat-induced anxiety[10]. 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[10]. 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[10]. 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[10]. More specifically, it is theorized that threat-induced anxiety may also be connected to deficits in resolving problems, which leads to uncertainty[10]. 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.
Dysfunctions
editStress
editExposure to severe stress may also be linked to damage in the DLPFC[11]. More specifically, acute stress has a negative impact on the higher cognitive function known as working memory (WM), which is also traced to be a function of the DLPFC[11]. In an experiment, researchers used functional magnetic resonance imaging (fMRI) to record the neural activity in healthy individuals who participated in tasks while in a stressful environment[11]. When stress successfully impacted the subjects, their neural activity showed reduced working memory related activity in the DLPFC[11]. These findings not only demonstrate the importance of the DLPFC region in relation to stress, but they also suggest that the DLPFC 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 more effective therapeutic stimulation[12].
References
edit- ^ a b c d Miller, Bruce L. (1999). The Human Frontal Lobes. New York, New York: The Guilford Press.[page needed]
- ^ Mansouri, F. A.; Buckley, M. J.; Tanaka, K. (2007). "Mnemonic Function of the Dorsolateral Prefrontal Cortex in Conflict-Induced Behavioral Adjustment". Science. 318 (5852): 987–90. doi:10.1126/science.1146384. PMID 17962523. S2CID 31089526.
- ^ Mansouri, Farshad A.; Tanaka, Keiji; Buckley, Mark J. (2009). "Conflict-induced behavioural adjustment: a clue to the executive functions of the prefrontal cortex". Nature Reviews Neuroscience. 10 (2): 141–152. doi:10.1038/nrn2538. PMID 19153577. S2CID 15181627.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: date and year (link) - ^ Mansouri, Farshad A.; Tanaka, Keiji; Buckley, Mark J. (2009). "Conflict-induced behavioural adjustment: a clue to the executive functions of the prefrontal cortex". Nature Reviews Neuroscience. 10 (2): 141–152. doi:10.1038/nrn2538. PMID 19153577. S2CID 15181627.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: date and year (link) - ^ Mansouri, Farshad A.; Tanaka, Keiji; Buckley, Mark J. (2009). "Conflict-induced behavioural adjustment: a clue to the executive functions of the prefrontal cortex". Nature Reviews Neuroscience. 10 (2): 141–152. doi:10.1038/nrn2538. PMID 19153577. S2CID 15181627.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: date and year (link) - ^ Barbey, Aron K.; Colom, Roberto; Grafman, Jordan (2013). "Dorsolateral prefrontal contributions to human intelligence". Neuropsychologia. 51 (7): 1361–9. doi:10.1016/j.neuropsychologia.2012.05.017. PMC 3478435. PMID 22634247.
- ^ Barbey, Aron K.; Colom, Roberto; Grafman, Jordan (2013). "Dorsolateral prefrontal contributions to human intelligence". Neuropsychologia. 51 (7): 1361–9. doi:10.1016/j.neuropsychologia.2012.05.017. PMC 3478435. PMID 22634247.
- ^ Kane, Michael J.; Engle, Randall W. (2002). "The role of prefrontal cortex in working-memory capacity, executive attention, and general fluid intelligence: An individual-differences perspective". Psychonomic Bulletin & Review. 9 (4): 637–71. doi:10.3758/BF03196323. PMID 12613671. S2CID 7992558.
- ^ Kane, Michael J.; Engle, Randall W. (2002). "The role of prefrontal cortex in working-memory capacity, executive attention, and general fluid intelligence: An individual-differences perspective". Psychonomic Bulletin & Review. 9 (4): 637–71. doi:10.3758/BF03196323. PMID 12613671. S2CID 7992558.
- ^ a b c d e Shackman, Alexander (April 2009). "Right Dorsolateral Prefrontal Cortical Activity and Behavioral Inhibition". Psychological Science. 20 (12): 1500–1506. doi:10.1111/j.1467-9280.2009.02476.x. PMC 2858783. PMID 19906125.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help)CS1 maint: date and year (link) - ^ a b c d Qin, Shaozheng; Hermans, Erno J.; Van Marle, Hein J.F.; Luo, Jing; Fernández, Guillén (2009). "Acute Psychological Stress Reduces Working Memory-Related Activity in the Dorsolateral Prefrontal Cortex". Biological Psychiatry. 66 (1): 25–32. doi:10.1016/j.biopsych.2009.03.006. PMID 19403118. S2CID 22601360.
- ^ Cohen, H.; Kaplan, Z; Kotler, M; Kouperman, I; Moisa, R; Grisaru, N (2004). "Repetitive Transcranial Magnetic Stimulation of the Right Dorsolateral Prefrontal Cortex in Posttraumatic Stress Disorder: A Double-Blind, Placebo-Controlled Study". American Journal of Psychiatry. 161 (3): 515–24. doi:10.1176/appi.ajp.161.3.515. PMID 14992978.