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Functional imaging of the brain has shown that self-control is correlated with an area in the dorsolateral prefrontal cortex (dlPFC), a part of the frontal lobe. This area is distinct from those involved in generating intentional actions, attention to intentions, or select between alternatives.[36] This control occurs through the top-down inhibition of premotor cortex.[37] There is some debate about the mechanism of self-control and how it emerges. Traditionally, researchers believed the bottom-up approach guided self-control behavior. The more time a person spends thinking about a rewarding stimulus, the more likely he or she will experience a desire for it. Information that is most important gains control of working memory, and can then be processed through a top-down mechanism.[38][39] Increasing evidence suggests that top down processing plays a strong role in self-control. Specifically, top-down processing can actually regulate bottom-up attentional mechanisms. To demonstrate this, researchers studied working memory and distraction by presenting participants with neutral or negative pictures and then a math problem or no task. They found that participants reported less negative moods after solving the math problem compared to the no task group, which was due to an influence on working memory capacity.[40][41] There are many researchers working on identifying the brain areas involved in the exertion of self-control; many different areas are known to be involved. In relation to self-control mechanisms, the reward centers in the brain compare external stimuli versus internal need states and a person’s learning history.[6][42] At the biological level, a loss of control is thought to be caused by a malfunctioning of a decision mechanism. A mechanistic explanation of self-control is still in its infancy. However, there is strong demand for knowledge about these mechanism because knowledge of these mechanisms would have tremendous clinical application. Much of the work on how the brain reaches decisions is based on evidence from perceptual learning. Many of the tasks that subjects are tested on are not tasks typically associated with self-control, but are more general decision tasks. Nevertheless the research on self-control is informed by more general research on decision tasks. Sources for evidence on the neural mechanisms of self-control include fMRI studies on human subject, neural recordings on animals, lesion studies on humans and animals, and clinical behavioral studies on humans with self-control disorders. There is broad agreement that the cortex is involved in self-control. The details of the final model have yet to be worked out. However, there are some enticing findings that suggest a mechanistic account of self-control could prove to have tremendous explanatory value. What follows is a survey of some of the important recent literature on the brain regions involved in self-control. Prefrontal cortex The prefrontal cortex is located in the most anterior portion of the frontal lobe in the brain. It forms a larger portion of the cortex in humans. The dendrites in the prefrontal cortex contain up to 16 times as many dendritic spines as neurons in other cortical areas. Due to this, the prefrontal cortex integrates a large amount of information.[43] The orbitofrontal cortex cells are important factors for self-control. If an individual has the choice between an immediate reward or a more valuable reward which they can receive later, an individual would most likely try to control the impulse to take that immediate reward. If an individual has a damaged orbitofrontal cortex, this impulse control will most likely not be as strong, and they may be more likely to take the immediate reinforcement. Additionally, we see lack of impulse control in children because the prefrontal cortex develops slowly.[44] Todd A. Hare et al. use functional MRI techniques to show that the ventromedial prefrontal cortex (vmPFC) and the dorsolateral prefrontal cortex (DLPFC) are crucially involved in the exertion of self-control. They found that activity in the vmPFC was correlated with goal values and that the exertion of self-control required the modulation of the vmPFC by the DLPFC. The study found that a lack of self-control was strongly correlated with reduced activity in the DLPFC. Hare’s study is especially relevant to the self-control literature because it suggests that an important cause of poor self-control is a defective DLPFC.[45] Outcomes as determining whether a choice is made Alexandra W. Logue is interested in how outcomes change the possibilities of a self-control choice being made. Logue identifies three possible outcome effects: outcome delays, outcome size, and outcome contingencies.[17] The delay of an outcome results in the perception that the outcome is less valuable than an outcome which is more readily achieved. The devaluing of the delayed outcome can cause less self-control. A way to increase self-control in situations of a delayed outcome is to pre-expose an outcome. Pre-exposure reduces the frustrations related to the delay of the outcome. An example of this is signing bonuses. Outcome size deals with the relative, perceived size of possible outcomes. There tends to be a relationship between the value of the incentive and the desired outcome; the larger the desired outcome, the larger the value. Some factors that decrease value include delay, effort/cost, and uncertainty. The decision tends to be based on the option with the higher value at the time of the decision. Finally, Logue defines the relationship between responses and outcomes as outcome contingencies.[17] Outcome contingencies also impact the degree of self-control that a person exercises. For instance, if a person is able to change his choice after the initial choice is made, the person is far more likely to take the impulsive, rather than self-controlled, choice. Additionally, it is possible for people to make precommitment action. A precommitment action is an action meant to lead to a self-controlled action at a later period in time. When a person sets an alarm clock, they are making a precommitted response to wake up early in the morning. Hence, that person is more likely to exercise the self-controlled decision to wake up, rather than to fall back in bed for a little more sleep. Cassandra B. Whyte studied locus of control and academic performance and determined that internals tend to achieve at a higher level. Internals may perceive they have options from which to choose, thus facilitating more hopeful decision-making behavior as opposed to dependence on externally determined outcomes that require less commitment, effort, or self-control.[46][47] Physiology of behavior Many things affect one's ability to exert self-control, but it seems that self-control requires sufficient glucose levels in the brain. Exerting self-control depletes glucose. Reduced glucose, and poor glucose tolerance (reduced ability to transport glucose to the brain) are correlated with lower performance in tests of self-control, particularly in difficult new situations.[48] Self-control demands that an individual work to overcome thoughts, emotions, and automatic responses/impulses. These strong efforts require higher blood glucose levels. Lower blood glucose levels can lead to unsuccessful self-control abilities.[49] Alcohol causes a decreas of glucose levels in both the brain and the body, and it also has an impairing effect on many forms of self-control. Furthermore, failure of self-control occurs most likely during times of the day when glucose is used least effectively. Self-control thus appears highly susceptible to glucose.[50] An alternative explanation of the limited amounts of glucose that are found is that this depends on the allocation of glucose, not on limited supply of glucose. According to this theory, the brain has sufficient resources of glucose and also has the possibility of delivering the glucose, but the personal priorities and motivations of the individual cause the glucose to be allocated to other sites. This theory has not been tested yet.[51] |
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