Motivation and emotion/Book/2019/Dorsolateral prefrontal cortex and long-term goal pursuit

Overview
"FOR THE ONE HUNDREDTH TIME, LIAM - GET UP OFF THE COUCH AND CLEAN YOUR ROOM, YOU SAID YOU WOULD KEEP IT CLEAN!"

Ah. Mum is yelling at me again. I often wonder why I'm so useless. If only there was some way to understand why I can't pursue any long-term goals.

"Sorry mum, I'll make sure to keep it clean".

Long-term goals are a major contributor to our daily functioning. They direct our actions, give us a sense of purpose, and shape our attitudes towards objects, people and circumstances. It is therefore critical we understand the importance in creating and achieving long term goals. Unfortunately it is easier said than done. There are numerous complexities in the cognitive functioning required to achieve long-term goals. This chapter examines:


 * 1) The role of the dorsolateral prefrontal cortex
 * 2) Typical functioning of the human brain
 * 3) How to achieve long-term goal pursuits
 * 4) Intrinsic motivation
 * 5) Potential enhancements of the dorsolateral prefrontal cortex

Frontal lobe


The frontal lobe is one of four major lobes in the human brain and is located at the front of each hemisphere. The frontal lobe is distinguished from the parietal lobe by the central sulcus, and separated from the temporal lobe by the lateral sulcus (Fuster, 2015).

The frontal lobe is further divided into functional areas. The primary motor cortex, premotor cortex, frontal eye fields, Broca’s area and the prefrontal cortex are the major functional areas within the frontal lobe.

Prefrontal cortex
The prefrontal cortex (PFC) covers the front-most part of the frontal lobe. The PFC is involved in personality expression, social behaviour, planning complex cognitive behaviour, and decision making (Fuster, 2015). The activity of the PFC is complex with researchers concluding that the PFC is responsible for executive functioning. The ability to differentiate among conflicting thoughts, separating differences between good and bad, better and best, and same and different, consequences, goal pursuits, expectations, and social norms is controlled by such executive functioning in the PFC (Fuster, 2015).

Fuster (2015) emphasised the functioning of the PFC in interpreting and representing information not readily available in the environment. The ability to represent information to pursue goals underlies all higher executive functioning. There have been several theories explaining the process the PFC undertakes utilising executive functioning. Top-down processing, the Dynamic Filtering Theory and the Integrative Theory of Prefrontal Cortex Function further explain the role of executive functioning in goal-pursuits.

The prefrontal cortex can be separated into two functionally different regions: the ventromedial prefrontal cortex (vmPFC) and the lateral prefrontal cortex (LPFC). From these two regions, the LPFC can be delineated into the dorsolateral (DLPFC) and ventrolateral (vl-PFC) areas, and the vmPFC can be delineated into the medial (mPFC) and ventral (vPFC) areas. Each of these areas are highly interconnected with areas of the brain responsible for attention, cognition, action and emotion (Fuster, 2015; Sturm, Haase & Lavenson, 2016).

Dorsolateral prefrontal cortex:


The DLPFC is a functional structure, rather than an anatomical structure, located in the middle frontal gyrus in humans. The DLPFC is a key structure responsible for many executive functions (Fuster, 2015; Striedter, 2005). Although not exclusively responsible, the DLPFC is required in all complex mental activity. The DLPFC is involved in planning, organisation, inhibition and abstract reasoning and several other executive functions (Fuster, 2015; Striedter, 2005). The DLPFC contains neural circuitry responsible for integrated responses such as sensory input, retaining short-term memory and motor signalling (Striedter, 2005). The DLPFC contains several connections to other cortices such as the temporal cortex, posterior parietal cortex, the premotor cortex and the retrosplenial cortex that allow the DLPFC to regulate brain activity, as well as be regulated by these cortices (Fuster, 2015).



{True or False? Attention is a function of the dorsolateral prefrontal cortex}


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Dorsolateral prefrontal cortex and goal-setting
The DLPFC is responsible for all new goal-directed sequences in activities involving behaviour, language, and reasoning (Fuster, 2015; Collins, 2008; Striedter, 2005). In the pursuit of goals, humans utilise prefrontal networks and interconnections in order to generate a plan of action, or schema (Fuster, 2015; Collins, 2008). This highly complex process is reliant on many cortical and subcortical brain regions that according to researchers the DLPFC initiates (Fuster 2015; Blumenfeld & Ranganath, 2007). The DLPFC is responsible for the structuring of behaviour and cognition in attaining biological and cognitive goals (Blumenfeld & Ranganath, 2007; Collins 2008).

As the DLPFC is at least partially responsible for integrated neuronal responses involving sensory input, retaining short-term memory, and motor signalling researchers have explained two further functions attributable to the role of the DLPFC and pursing goals. First, a retrospective function of short-term memory and the second, a prospective function of preparatory set (or expectation). These two functions share overlapping networks of the DLPFC and have been theorised to bridge time between sensory and motor events. Such bridging enables humans to maintain long term goals and achieve them through the control of motor output and sensory input.

The dorsolateral prefrontal cortex and working memory
Fuster (2015) concluded that the DLPFC is critically involved in forms of working memory in order to achieve a goal. The evidence primarily comes from two methodologies: selective inactivation of the DLPFC and single-cell recording. Smith and Jonides (1999) measured the activation of the DLPFC during working memory and concluded that an activation in the DLPFC supports mobilisation for future action.

In order to measure the executive role of the DLPFC in goal pursuits, researchers analysed how managing expectation and memory occur on a neuronal level. Researchers monitored the progressive increase of cell discharge and slow surface-negative potentials of subjects before a stimulus-contingent act. This indicates that memory and expectation can function simultaneously (Smith & Jonides, 1999). Such activity of cells manifests in the human ability to focus attention on a motor act to ensure efficient execution.



Current research further acknowledges the role of the DLPFC in working memory. Kobayashi (2009) analysed the influences of rewards on activity in the DLPFC in monkeys. Kobayashi (2009) concluded that DLPFC neurons are sensitive to many aspects of reward: quantity, quality, availability, and delay. Kobayashi theorised two potential possibilities for the high sensitivity of reward on the DLPFC: first, that the DLPFC receives reward information from the orbitofrontal cortex, and the second is the response of mesencephalic dopamine neurons located in the DLPFC.

Understanding the role of working memory and short-term goals on the DLPFC is critical for evaluating the role of the DLPFC and long-term goal pursuits according to Woolley and Fishbach (2016). The DLPFC has a role in the assessment of a cost-benefit analysis, and immediate rewards greater influence cost-benefit analyses. For instance, individuals attempting to lose weight may join a gym with the long-term goal to lose weight. As there is a major delay between consistent exercise and losing weight, individuals are likely to give up on their weight-loss journey. There is a tendency to evaluate the cost of time and energy against their final goal of losing weight. Such cost-benefit analysis acknowledges a major delay between reaching the reward of their goal. Conversely, when individuals can incrementally reward themselves, a cost-benefit analysis is undertaken with the benefit (or reward) having shorter delays, resulting in higher motivation of the individual. It is therefore critical to acknowledge the role of the DLPFC’s dopamine reward circuits, involving mesencephalic dopamine neurons, in planning and achieving short-term goals and the effect of achievement on long-term goals (Ballard et al., 2011).

As the DLPFC is largely responsible for many executive functions, it plays a pivotal role in mechanisms of self-control (Mansouri, Koechlin, Rosa & Buckley, 2017; Fishbach & Trope, 2005). Fishbach and Trope (2005) investigated how self-control over the attention and valuation of delayed rewards affected immediate temptation. Such self-control dilemmas focus on the role of perception of sensory information to influence motivation (Fishbach & Trope, 2005). For instance, a student who debates between studying (long-term reward) or partying (short-term reward) is more likely to study if they consider the delayed rewards of studying (obtained degree) against the delayed rewards of partying (likely to be none), instead of the immediate rewards for each possibility. Executive functioning relating to self-control suggests that intrinsic motivation plays a significant role in long-term goal pursuits.

The year is 1848, Phineas Gage is about to become a legend in the psychology community.

While packing a hole full of gun powder with an iron rod, the powder detonated and the iron rod was launched into Gage's head. Unbelievably, Gage survived the incident. After the incident, Gage was unlike he was earlier, his personality had changed. His misfortune became the ground work for understanding the location of particular functions of the brain (Garcia-Molina, 2012).

Goal-setting theory
Edwin Locke (1968) generated a theory measuring the effects of setting goals on performance. Consistent findings show that individuals who set specific, difficult goals, performed better than those with vague, less difficult goals. More recently, Locke and Latham (2002) have revisited goal-setting theory and have updated five basic principles in order to best achieve long-term goals:

1.   Clarity: Goals must be clear and specific.

2.   Challenge: There must be a decent level of difficulty in order to motivate individuals to strive for goals.

3.   Commitment: There must be deliberate effort to meet the goal.

4.   Feedback: Receiving information on how to best progress toward your goal influences achieving long-term goals.

5.   Task Complexity: If the task is difficult, ensure a realistic time-frame has been given to achieve and overcome obstacles.

 {True or False? It is necessary to receive feedback in order to best achieve your goal.}


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+ True - False

Motivation
Motivation can be divided into two different types of motivation: Intrinsic and Extrinsic motivation. As the purpose of this chapter is to evaluate the role of the DLPFC in long-term goal pursuits, this chapter will only display intrinsic motivation.

Intrinsic motivation
Intrinsic motivation is a behaviour that is driven by internal drives. Instead of external pressures or desires to be motivated, there is an emphasis on interest or enjoyment of the task itself (internal drives). Individuals who are intrinsically motivated are more likely to engage in a task willingly in order to improve their skills, and are more likely to achieve long term goals (Richard & Edward, 2000).

The DLPFC has a strong relationship with the dorsal anterior cingulate cortex (dACC) as both areas are responsible for monitoring errors and in behavioural adaptation. Such functioning plays a critical role in long-term goal pursuit (Ng, 2018). As per Locke’s Goal-Setting Theory (1968), it is most beneficial for individuals to understand particular obstacles or difficulties, as well as have the perceived ability to complete a task when pursuing goals.

Dopamine is considered a key substrate of intrinsic motivation in goal-setting (Ballard et al., 2011; Ng, 2018). Attentiveness and behavioural engagement are two functions of dopamine that directly impact the functioning of intrinsic motivation (Ng, 2018). Dopamine enables the successful behaviour in accordance with goals (Ng, 2019; Ott & Nieder, 2019). There is a great reliance on the dopamine systems in the prefrontal cortex, utilising the Dopamine Reward Circuit, to regulate functioning (Ballard et al., 2011).

 {True or False? Intrinsic motivation refers to motivators such as enjoyment}


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Enhancements of the functioning of the DLPFC
Research has demonstrated that obscurities in the DLPFC are present in those diagnosed with mental illnesses such as schizophrenia. As a result, new information pertaining to the correction of neuronal processes is being sought after by researchers.

Natural enhancements
Kumari et al. (2011) conducted a study to measure the rate of increased activation of connections in the prefrontal brain region associated with psychotic symptoms. Kumari et al. (2011) used a functional MRI (fMRI) to see how patients processed black and white images of facial expressions such as fear and anger. The fMRI initially showed how particular increased activation of connections in the prefrontal brain region was associated with psychotic symptoms such as delusions. Patients were then required to undergo six months of cognitive behavioural therapy (CBT). After the six months, an fMRI showed that there was heightened activity between the DLPFC and the amygdala. This heightened activity demonstrated a reduction in threat processing when viewing different facial expressions. The CBT also induced greater connectivity between the dorsolateral prefrontal cortex and the post-central gyrus in the parietal lobe. This associated contributed to either full or partial remission of psychotic symptoms.

Unfortunately, this study also had several limitations. The study has been criticised for having a high potential for a type II error as there was a high attrition rate. Furthermore, the generalisability of the results into clinical practice is poor as facial affective processing tasks are not common place in clinical practice.

Despite such limitations, the results cannot be ignored and more research should be conducted regarding brain connectivity changes associated with psychotherapy, and how this may help long-term recovery from mental illness. More specifically, changes in the DLPFC’s executive functioning and cross-cortical communication must be researched

Artificial enhancements
Beyond natural enhancements to the DLPFC, a lot of research has been conducted regarding medication and transcranial direct current stimulation. Recently there has been a push in research regarding the side effects and the role of medication on the frontal lobe.

Guanfacine
Current medications such as guanfacine are currently being prescribed to individuals with ADHD (Attention Deficit Hyperactivity Disorder) (Cruz, 2010). Guanfacine focuses on the inhibition of impulsive choices through the strengthening of attention and behaviour affecting neurons in the DLPFC (Cruz, 2010). Guanfacine strengthens prefrontal cortical synaptic connectivity and enhances neuronal firing. Guanfacine has the potential to influence long-term goal pursuit through the benefits of executive functioning influencing attention.

Unfortunately there are several side effects. Common side effects includes sleepiness, constipation, drowsiness and constipation. More severe side effects can include anxiety, low blood pressure, and depression (Cruz, 2010).

Modafinil
Modafinil is another medication often used to enhance motivation of individuals diagnosed with disorders relating to motivation (Robertson & Hellriegal, 2003). Modafinil has been the target of several studies, with a focus on the effect of modafinil on dopamine and brain functioning. Zolkowska et al. (2009) found that modafinil significantly affects the dopamine transporter and acts as a dopamine reuptake inhibitor, which are known to help in the treatment of ADHD and narcolepsy.

Modafinil is known as an atypical dopamine reuptake inhibitor as there is low potential for substance abuse (Zolkowska et al., 2009). By altering dopamine functioning in the DLPFC, executive functioning decisions change and have potential to influence long-term goal pursuits.

Unfortunately much like guanfacine there are several negative side effects of modafinil including: headache, anxiousness, back pain, nausea, and sleep problems (Robertson & Hellriegal, 2003). There is also a lot of inconclusive research on the rate of addiction for the long-term use of modafinil.

Transcranial direct current stimulation
Javadi and Walsh (2012) analysed whether transcranial direct current stimulation (tDCS) affects the human working memory. Anodal and cathodal stimulation was applied over the left DLPFC. During encoding of information, anodal stimulation of the left DLPFC improved memory, whereas cathodal stimulation of the same area impaired memory performance. The results of the study indicated that active stimulation of the left DLPFC can lead to an enhancement of memorisation. Such short-term memory effects have the potential to influence long-term goal pursuits.

With each artificial enhancement, more information needs to be done measuring the effects of both medication and tDCS on long-term goal pursuits (Yang, Gao, Shi, Ye & Chen, 2017). Although information can be inferred from the functioning of the DLPFC, more conclusive research is needed. Furthermore, the side effects of medication may prove too great to warrant further investigation.

 {True or False? Modafinil is considered a dopamine reuptake inhibitor.}


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Future direction for research
Future direction for research needs to focus on long-term goal pursuits. There is little research on the relationship between the DLPFC and long-term goal pursuits.

As the DLPFC is at least partially responsible for executive functioning and relies on communicating with several other cortices to function, research would benefit from further conceptualising the DLPFC. Analysing the role of the DLPFC and long-term goal pursuits may oversimplify numerous processes of executive functioning.

Future research could also consider the clinical significance of changes to the DLPFC. Current research on the relationship of CBT and the DLPFC is interesting and may prove clinically beneficial for patients. More research should measure the neuronal changes resulting from CBT. Future research may also consider the combined effect of medication and CBT on the DLPFC and how this may effect disorders such as schizophrenia and ADHD.

Conclusion
The role of the DLPFC in long-term goal pursuits is complex and involves various cross-cortical functioning. The biggest predictors of achieving long-term goals are identified as achieving short-term goals, reward systems, and cognitive differences in executive functioning. It is therefore imperative to analyse the relationship the DLPFC has with these variables. Currently, it is understood that long-term goals involve various cortices and sub-cortices.

Research currently draws inferences as to how the DLPFC effects long-term goal pursuits. These inferences are based on the functions of the DLPFC, and therefore research is concerned with the effect of a particular function on long-term goals. These functions occur cross-cortically adding to the complexity in conclusively suggesting the role of the DLPFC in long-term goal pursuits. More conclusive longitudinal studies must be conducted analysing the role of the DLPFC in order to conclusively report the role of the DLPFC in long-term goal pursuits.