Ventrolateral prefrontal cortex
Psychlopedia -- Key concepts -- Biological concepts -- Ventrolateral prefrontal cortex
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The prefrontal cortex represents regions in the front section of the frontal lobes. The prefrontal cortex is often divided into several regions such as the ventrolateral, dorsolateral, orbitofrontal, ventromedial, basal, orbital, and frontopolar areas. The ventrolateral and dorsolateral regions are located on the side of these frontal lobes. In the diagram below, the bottom red patch in the left figure is the ventrolateral prefrontal cortex, and the top red patch in the left figure is the dorsolateral prefrontal cortex.
The ventrolateral prefrontal cortex mediates some of the cognitive responses to negative emotions. In particular, depression seems to activate the left ventrolateral prefrontal cortex, which in turn enables individuals to maintain their focus on a specific and consequential problem, minimizing distractions. Anxiety appears to activate the right ventrolateral prefrontal cortex, which enhances the vigilance of individuals to anticipated hazards.
The ventrolateral prefrontal cortex is sometimes called the inferior frontal cortex. This structure corresponds to Brodmann's Areas 44, 45, and 47.
Roles of the ventrolateral prefrontal cortex and dorsolateral prefrontal cortex
The difference between the ventrolateral prefrontal cortex and dorsolateral prefrontal cortex roughly aligns to the disparity between the ventral and dorsal pathways of the cortex, according to O'Reilly (2010). The ventral pathway, which is significantly underpinned by the temporal cortex, attempts to characterize the features and attributes of the stimuli in the environment, sometimes called the what system. The dorsal pathways, which is primarily underpinned by the parietal cortex, attempts to characterize the spatial relationships between stimuli and to ascertain which responses should be executed, called the how system.
The ventral pathways primarily terminate in the ventrolateral prefrontal cortex instead of the dorsolateral prefrontal cortex. Presumably, which features or attributes of the environment should be processed depends on the goals of individuals. The ventrolateral prefrontal cortex represents these goals and thus affects which features or attributes are extracted. That is, the ventrolateral prefrontal cortex biases or controls the ventral pathways.
The dorsal pathways primarily terminate in the dorsolateral prefrontal cortex instead of the ventrolateral prefrontal cortex. The dorsolateral prefrontal cortex represents complex relationships that can be applied, such as mathematical rules or other algorithms, to convert stimuli into responses. The dorsolateral prefrontal cortex, for example, may be able to retain a rule that was imposed a few minutes ago onto the dorsal pathway to ensure responses apply to these constraints.
O'Reilly (2010) accumulated considerable evidence to support this contention. For example, in one study, when individuals needed to differentiate stimuli that differ only on subtle semantic properties, demanding the what system, the ventrolateral prefrontal cortex was activated significantly. In contrast, when individuals needed to apply complex rules to decide which responses to execute, but the stimuli could be readily differentiated, the dorsolateral prefrontal cortex was activated significantly (Nagel et al., 2008).
Organization of the ventrolateral prefrontal cortex
Many studies indicate that broad or abstract concepts, such as "mammal", are represented towards the front or rostral regions of the prefrontal cortex. In contrast, more specific or tangible concepts, such as "dog", are represented caudally. According to O'Reilly (2010), this distinction between abstract and concrete representations probably pertains to the ventrolateral prefrontal cortex. For example, Brodmann area 47 may represent more abstract information than Brodmann area 44.
Functions of the ventrolateral prefrontal cortex
Control of attention
Several strands of research indicate the left ventrolateral prefrontal cortex facilitates the capacity of individuals to control attention and to resist temptations. In particular, when individuals deliberate over problems, they need to divide the issue into its constituent facets, consider these facets in sequence, maintaining any insights in an active state--all demanding working memory (Baddeley, 2007). Unfortunately, distractions that are extraneous to an ongoing problem, such as irrelevant noises, can supersede some of the information and insights that need to be retained in an active state. That is, only a limited array of insights can be maintained in this state. To sustain thoughts about the ongoing problem, individuals must be able to deflect these distractions. This deflection of distractions is called attentionnal control.
This need to control attention increases as the load on working memory escalates. That is, researchers often manipulate the amount of information that needs to be retained to complete some task, using activities such as Raven's Advanced Progressive Matrices. When the burden on working memory increases, the left ventrolateral prefrontal cortex is more likely to be activated-as several neuroimaging studies have shown (e.g., love, Haist, Nicol, & Swinney, 2006; Wolf, Vasic, & Walter, 2006). These findings, according to several researchers, indicate that activation of the left ventrolateral prefrontal cortex might underpin the control of attention (D'Esposito, Postle, & Rypma, 2000).
Indeed, scholars have attempted to characterize how the left ventrolateral prefrontal cortex might facilitate the control of attention. Research indicates that neurons in the left ventrolateral prefrontal cortex continue to discharge, despite delays and distractions (e.g., Jonides & Nee, 2006). To illustrate, in some studies, individuals need to memorize some stimulus. Some neurons in the left ventrolateral prefrontal cortex begin to discharge when the stimulus is first presented and encoded. This activation is largely maintained during the retention period (e.g., Rao, Rainer, & Miller, 1997). These cells remain active despite distractions (e.g., Postle, 2006). Hence, these cells might enable individuals to maintain focus on a target stimulus in distracting environments.
Similarly, the left ventrolateral prefrontal cortex is especially active when distracters are prevalent. For example, in some studies, a series of stimuli, such as letters are presented. Occasionally, one of the stimuli is presented in a different color. Participants must press a specific button if this stimulus is identical to the letter that was presented three items earlier, called the three back task. In the sequence, Z Y X A Y, for example, participants would need to press this button if the final stimulus appeared in a different color. In the sequence, Z X Y A Y, however, they would not press this stimulus, Nevertheless, in this example, the final stimulus is identical to the letter that appeared two items earlier. Participants might experience a momentary inclination to press the button-an inclination they must suppress, demanding control of attention. The left ventrolateral prefrontal cortex seems to be especially active on these trials (Kane, 2005; Kane & Engle, 2002).
Some evidence indicates the right ventrolateral prefrontal cortex underpins vigilance. That is, when this region is activated, individuals scan the environment, striving to detect a potential hazard or threat. Consistent with this premise, anxiety, which tends to coincide with this vigilant state activates the ventrolateral prefrontal cortex, especially the right side, whereas depression tends to activate the left ventrolateral prefrontal cortex (for a reviews, see Andrews & Thompson, 2009). In addition, difficult vigilance tasks-for example, tasks in which the search criteria varies across trials--activates the right ventrolateral prefrontal cortex (Monk, Nelson, McClure, Mogg, Bradley, Leibenluft, et al., 2006).
Inhibition of social pain
The ventrolateral prefrontal cortex enables individuals to resolve the negative feelings that social exclusion can elicit. That is, in many settings, individuals might feel rejected or excluded. They might, for example, not be invited to a party. Activation of the ventrolateral prefrontal cortex seems to resolve the unpleasant feelings that such rejection or exclusion can elicit. Presumably, consistent with the importance of this region to the resistance of temptations, the ventrolateral prefrontal cortex may enable individuals to direct attention to helpful solutions rather than ruminate over problems.
To demonstrate the role of this region, Yanagisawa, Masui, Onoda, Furutani, Nomura, Yoshida, and Ura (2011) undertook a study in which participants completed a measure of the behavioral inhibition system and the behavioral activation system (see reinforcement sensitivity theory). The behavioral inhibition system represents the degree to which individuals are sensitive to problems, like mistakes or criticisms. The behavioral activation system represents the degree to which individuals are sensitive to rewards and excitement. Furthermore, these individuals participated in an online game with other people. Some of these individuals were excluded by everyone else, whereas other individuals were included. During this task, near-infrared spectroscopy was applied to measure activity in the ventrolateral prefrontal cortex. Finally, the degree to which they felt a sense of belonging, self esteem, control, and meaning were assessed.
Unsurprisingly, when the behavioral inhibition system was activated--and thus individuals reported sensitivity to problems--exclusion was especially likely to impede their needs, decreasing any sense of belonging, self esteem, control, and meaning. This relationship was mediated by limited activation of the ventrolateral prefrontal cortex. That is, if people are sensitive to problems, activation of the ventrolateral prefrontal cortex in response to problems is limited. Hence, the capacity of these individuals to curb rumination and to resolve their pain diminishes.
Activation of the ventrolateral prefrontal cortex
Cells in dorsal raphe nucleus, which is a structure located in the midbrain, often activate the ventrolateral prefrontal cortex. That is, the need to control attention seems to activate the dorsal raphe nucleus. Serotonergic neurons, projecting from the dorsal raphe nucleus, activate the ventrolateral prefrontal cortex.
Feelings of dejection or depression seems to activate the left ventrolateral prefrontal cortex. As neuroimaging studies show, depression seems to coincide with elevated activation of the ventrolateral prefrontal cortex, with a bias towards the left side. This finding persists regardless of whether or not this emotional state is induced or existed already (see Drevets, 1999, 2000; Pardo, Pardo, & Raichle, 1993).
Conceivably, the association between these negative mood states and activation of the left ventrolateral prefrontal cortex implies that depression might be functional in some contexts. Specifically, depression, which activates the left ventrolateral prefrontal cortex, might enhance the capacity of individuals to control attention, ensuring that target problems are considered exhaustively and solved effectively (cf., Andrews & Thompson, 2009).
As Dulebohn, Conlon, Sarinopoulos, Davison, and McNamara (2009) found, when individuals feel that procedures are unfair or unjust, the ventral lateral prefrontal cortex on both sides, together with the superior temporal sulcus, tend to be activated. In contrast, when individuals receive unfair outcomes, different regions, such as the anterior cingulate, insular cortex, and dorsolateral prefrontal cortex on both sides, are activated.
Specifically, Dulebohn, Conlon, Sarinopoulos, Davison, and McNamara (2009) undertook a study to ascertain whether unfair procedures, called procedural justice, and unfair outcomes, called distributive justice, evoke the same cognitive processes. In this study, individuals participated in the ultimatum game (see games). Both they and another person were assigned to one of two roles: the proposer and the responder. The proposer was first granted $10. This individual was then encouraged to offer a certain percentage to the other person, designated as the responder. The proposer might, for example, offer $2 or $5 to the responder. The responder can then either accept or reject the offer. If the offer is rejected, both individuals receive no money.
To decide which person would be the proposer and which person would be the responder, participants completed a series of mathematics questions. They were told the person who answered the most questions correctly would be the proposer--the preferred role. However, for some participants, procedural justice was violated. For example, the decision was derived from only one of the questions, or some other feature of the procedure was not followed. Furthermore, for some participants, distributive justice was violated: That is, when they were the responder, they were offered only $1 or $2 from the $10.
As fMRI imaging showed, procedural injustice activated the ventral lateral prefrontal cortex as well as the superior temporal sulcus. Generally, the ventral lateral prefrontal cortex is activated to resolve social problems. The superior temporal sulcus is activated to understand the intentions of other people, called theory of mind, vital to social processing. These findings, thus, imply that procedural injustice violates the social expectations of individuals. They feel rejected, as implied by the activation of the ventral lateral prefrontal cortex, as well as attempt to understand the intentions that incited this rejection, as implied by the activation of the superior temporal sulcus.
In contrast, distributive injustice activated the anterior cingulate, insular cortex, especially the anterior portion, and the dorsolateral prefrontal cortex. The anterior cingulate is activated when individuals experience a sense of conflict, in this instance between hopes and outcomes. The insular cortex underpins the experience and expectation of negative emotions. The dorsolateral prefrontal cortex is activated presumably to regulate the negative emotions. That is, when this region is activated, individuals formulate important goals, partly to inhibit the effects of negative emotions on behavior.
These findings thus verify the distinction between procedural and distributive injustice. Procedural injustice primarily undermines social trust. Distributive injustice, in contrast, activates more activated negative emotions, such as resentment and anger.
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Created by Dr Simon Moss on 11/08/2009
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