**2.1. Executive functions and prefrontal cortex**

in society also faces difficulties in social participation. A child who is not able to observe the wide range of perspectives, or a wide range of options offered during a group event, is usually incomplete in executive functions, and it is possible to observe that a child with faults on executive functions is affected by more than one area of socialization and academic skills [18, 19].

Adolescence, in other words, upper cognitive access, is an important period in which an individual is able to make a strategic choice to increase learning capacity, evaluate options, and meet that demand. Ongoing development of the executive neural network (frontal lobe) explains the inconsistencies of high-level skills of adolescence [20]. Frontal functions, especially the dorsolateral prefrontal cortex and the orbitofrontal cortex areas, gradually begin to engage. In addition, there is a marked decrease in the gray matter of the cortex and an increase in white matter during this period [21]. While these important changes in brain structure change social awareness and expectations in this period, hormonal and physical changes improve the interaction between the individual and the environment [22]. For this reason, adolescents' capacities of awareness, decision-making, and problem-solving, which are highly affected by cognitive skills and emotional, social, and physical situations, also vary [23]. As a result, it is theorized that the development of executive functions in adolescence may be modulated in an emotional or social context. Luna and Sweeney also described adolescence as a "transition to an effective working relationship with the brain." During the adult period, executive networks become more consolidated and refined. Actions are more in sync with behaviors and interact more with

Increasing independence and its capacity and managing multidimensional learning and behavioral demands develop during this period. This is a reflection of progress in the areas of attention control, flexibility and processing speed, capacity and working memory, planning, and problem-solving in conjunction with the increase in frontal cortex pruning and myelin-

While Anderson believes that cognitive flexibility and target-setting capacity mature up to the age of 12, some researchers later argue that executive functioning, memory, impulse control, and planning continue to evolve considerably in adolescence and early adulthood [26]. This theory was more widely accepted because of the proliferation of synapses at the beginning of adolescence. These developments turn into emotional decision-making and less responsive reactions to the will of the environment, and this is an appropriate response to the theory of

Disorder in the development of executive control during adolescence is present in psychopathology. The capacity to think before moving, to assess the appropriateness of one's answer, and to determine the most effective action that gives the desired result often varies in adolescence. However, in a typically developing young person, these skills become increasingly more effective over time [27]. Young people with impaired executive functions cannot make effective choices and cannot reach the result. In fact, while adolescents are more conscious at the beginning of pubertal maturation, they then enter into risky and sometimes reckless behavior and become more sensitive to others' views and assessments. This can make their

**1.3. Executive functions in adolescents**

32 Occupational Therapy - Therapeutic and Creative Use of Activity

others with better behavioral and emotional control [24].

ization that occurs during adolescence [25].

relationships difficult with peers and adults [20].

self-control and social rules [27].

Executive functions are interdependent and progressively acquired; high-level cognitive skills that occur in conjunction with the expansion and integration of cerebellar, subcortical, and prefrontal nerve networks during early childhood and adolescence until early adulthood. Because the development of nervous systems that support executive functions lasts too long, they are vulnerable to changes that occur during development, which can lead to multiple executive dysfunctions [20].

The prefrontal cortex has an important role in the development of executive functions. The prefrontal cortex is located in the anterior part of the premotor cortex and constitutes approximately one-third of the cortex (**Figure 1**). The neural connections between the prefrontal cortex, motor and sensory cortices, and the brain's subcortical structures are carefully regulated and are responsible for controlling, influencing, and regulating behavioral goals and behaviors. As the individuals mature, large neural networks that are responsible for learning and behavior become increasingly integrated and coordinated with prefrontal cortex-related networks. As a result, the regulation of high skill levels that lead to many behaviors is related to the neurodevelopmental processes of the mature brain. This contributes to the enhancement of coordination of communication and behavioral regulation related to executive functions [21].

At the beginning of life, subcortically managed neural processing is the primary ability to interact and understand sensory input, to interact more extensively with the environment, and to reinforce and remember these experiences over time. These experiences reinforce the link between more integrated sources of knowledge that are better understood by the ongoing myelination of the more integrated and mature brain (**Figure 2**). As the connections between the subcortical structures and the prefrontal cortex increase, attention and memory control increases. In infants and children who begun to walk, growth episodes are associated with increases in attention control and working memory capacity. Subsequent brain growth episodes occur at 6–8, 10–12, and 14–16 years of age. Coordination between the prefrontal cortex and regulatory and executive networks improves the communication further [22].

**Figure 1.** Prefrontal cortex.

example, when children and adults were assessed for "Go/No-Go" tasks, while both groups showed functional magnetic resonance imaging (fMRI) activation in the anterior cingulate cortex, orbitofrontal cortex, and lower and middle frontal glands (**Figure 3**), children showed more activation on the anterior cingulate cortex and prefrontal cortex than adults [29]. These findings suggest that children work in wider areas of the prefrontal cortex during inhibitor tasks compared to adults. In a similar study, the increase in cortical activation on the left inferior frontal gyrus and orbitofrontal cortex due to the age is further emphasized; also it was shown that the activation of the left upper and middle frontal gyrus and anterior cingulate

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Another study that tackles the relationship between conflict resolution and cortical activation in children and adults, using event-related potentials, supports that executive functions

**Functions of the prefrontal cortex:** *Inhibitory control* is described as the basis of the executive functions. Anterior prefrontal cortex is defined as the responsible area for impulse control in walking children and adolescence [31]. Impulse control processes are lateralized in the right hemisphere and are connected to the parietal lobes via ventral prefrontal cortex. At the same time, orbitofrontal cortex, anterior cingulate cortex, parietal and temporal cortex, and gyrus rectus are responsible for the impulse control [32]. A group of children with normal development, the ages between 4 years, 4 months, and 6 years, 8 months is the highest age for the cortex activation level with the working memory task [33]. This suggests that important morphological and structural changes affecting impulse control occur in the prefrontal cortex

*Working memory* depends on the prefrontal cortex activation, and tasks related to working memory development are age-related (especially during childhood) [32]. In the prefrontal cortex, in particular, the left middle frontal gyrus and the lower frontal gyrus are associated with working memory. The mid-frontal gyrus also plays a role in the control of automatic behaviors and competing answers and in responding to conflicting emotional intelligence. The right middle frontal gyrus is associated with judgmental response and the organization

*The shifting*, interaction with the prefrontal cortex, and its activation is a common finding with the adult period. The prefrontal cortex produces a strategy against the surrounding

become more productive as the brain signals become more mature [30].

and the connected brain regions during childhood and adolescence.

**Figure 3.** Dorsolateral prefrontal cortex, orbitofrontal cortex and anterior cingulate cortex.

of the activity used to reach a goal [34].

cortex decreased with age.

**Figure 2.** Development of the dorsolateral prefrontal cortex.

In the first years of life, the prefrontal cortex grows with its expanding nets which leads to the development of facilitation and memory increase. As the child progresses toward middle childhood, connections related to prefrontal cortex and communication develop. The development of the prefrontal cortex accelerates the development of information processing and cognitive flexibility between the ages of 7 and 9 years. These developments in the frontal system and related networks encourage the analysis and integration of complex information and the communication needed for effective decision-making. The prefrontal cortex is especially involved in impulse control and the following strategy development and self-monitoring [23].

Given the central role of the prefrontal cortex in the successful development of executive functions, lesions of this critical region have been associated with memory weakness, impulsivity, attention problems, and disorganization. It is known that the damage of the left dominant prefrontal cortex causes particularly the impairment of the divided attention. Contrary to the lateral prefrontal cortex, regions associated with the ventral and medial prefrontal cortex show strong neural connections toward the limbic system and amygdala and are therefore responsible for the integration of mainly emotional and nonemotional information. Given the nature of this relationship, damage to the medial prefrontal cortex means impaired activity initiation, and individuals with lesions in this region are typically irrelevant, flat, and unmotivated [24–26].

It is difficult to determine the contribution of a particular cortical area over the executive functions. Although studies to this date have indicated that the main area control is related to the prefrontal cortex and the component structures, it is seen that the indefinite variability persists. Although some investigations suggest that some aspects of executive functions may be related to certain subregions of the prefrontal cortex, much of this work has been completed with adult and nonhuman specimens [28]. For this reason, the age in which brainstem connections of executive functions are established and whether these distinctions are appropriate for children or not are yet unknown. Preliminary studies, however, show that children have larger and less specific work in brain regions during executive functions. For example, when children and adults were assessed for "Go/No-Go" tasks, while both groups showed functional magnetic resonance imaging (fMRI) activation in the anterior cingulate cortex, orbitofrontal cortex, and lower and middle frontal glands (**Figure 3**), children showed more activation on the anterior cingulate cortex and prefrontal cortex than adults [29]. These findings suggest that children work in wider areas of the prefrontal cortex during inhibitor tasks compared to adults. In a similar study, the increase in cortical activation on the left inferior frontal gyrus and orbitofrontal cortex due to the age is further emphasized; also it was shown that the activation of the left upper and middle frontal gyrus and anterior cingulate cortex decreased with age.

Another study that tackles the relationship between conflict resolution and cortical activation in children and adults, using event-related potentials, supports that executive functions become more productive as the brain signals become more mature [30].

**Functions of the prefrontal cortex:** *Inhibitory control* is described as the basis of the executive functions. Anterior prefrontal cortex is defined as the responsible area for impulse control in walking children and adolescence [31]. Impulse control processes are lateralized in the right hemisphere and are connected to the parietal lobes via ventral prefrontal cortex. At the same time, orbitofrontal cortex, anterior cingulate cortex, parietal and temporal cortex, and gyrus rectus are responsible for the impulse control [32]. A group of children with normal development, the ages between 4 years, 4 months, and 6 years, 8 months is the highest age for the cortex activation level with the working memory task [33]. This suggests that important morphological and structural changes affecting impulse control occur in the prefrontal cortex and the connected brain regions during childhood and adolescence.

In the first years of life, the prefrontal cortex grows with its expanding nets which leads to the development of facilitation and memory increase. As the child progresses toward middle childhood, connections related to prefrontal cortex and communication develop. The development of the prefrontal cortex accelerates the development of information processing and cognitive flexibility between the ages of 7 and 9 years. These developments in the frontal system and related networks encourage the analysis and integration of complex information and the communication needed for effective decision-making. The prefrontal cortex is especially involved in impulse control and the following strategy development and self-monitoring [23]. Given the central role of the prefrontal cortex in the successful development of executive functions, lesions of this critical region have been associated with memory weakness, impulsivity, attention problems, and disorganization. It is known that the damage of the left dominant prefrontal cortex causes particularly the impairment of the divided attention. Contrary to the lateral prefrontal cortex, regions associated with the ventral and medial prefrontal cortex show strong neural connections toward the limbic system and amygdala and are therefore responsible for the integration of mainly emotional and nonemotional information. Given the nature of this relationship, damage to the medial prefrontal cortex means impaired activity initiation, and individuals with lesions in this region are typically irrelevant, flat, and unmo-

**Figure 2.** Development of the dorsolateral prefrontal cortex.

34 Occupational Therapy - Therapeutic and Creative Use of Activity

It is difficult to determine the contribution of a particular cortical area over the executive functions. Although studies to this date have indicated that the main area control is related to the prefrontal cortex and the component structures, it is seen that the indefinite variability persists. Although some investigations suggest that some aspects of executive functions may be related to certain subregions of the prefrontal cortex, much of this work has been completed with adult and nonhuman specimens [28]. For this reason, the age in which brainstem connections of executive functions are established and whether these distinctions are appropriate for children or not are yet unknown. Preliminary studies, however, show that children have larger and less specific work in brain regions during executive functions. For

tivated [24–26].

*Working memory* depends on the prefrontal cortex activation, and tasks related to working memory development are age-related (especially during childhood) [32]. In the prefrontal cortex, in particular, the left middle frontal gyrus and the lower frontal gyrus are associated with working memory. The mid-frontal gyrus also plays a role in the control of automatic behaviors and competing answers and in responding to conflicting emotional intelligence. The right middle frontal gyrus is associated with judgmental response and the organization of the activity used to reach a goal [34].

*The shifting*, interaction with the prefrontal cortex, and its activation is a common finding with the adult period. The prefrontal cortex produces a strategy against the surrounding

**Figure 3.** Dorsolateral prefrontal cortex, orbitofrontal cortex and anterior cingulate cortex.

information. This situation changes with regional activation differences, intelligence, and age. An event-related fMRI study investigated the performance of young adults and adults in the task of shifting attention using intelligence quotient (IQ) as a covariant and found that the average IQ individuals showed a higher activation of both prefrontal cortex and anterior cingulate cortex during the activation of response [35]. During the feedback, participants in the high IQ group showed a more complex relationship, including parietal, caudate, fusiform, and occipital regions. The authors reported that the feedback of high IQ people may be more strategic and they may experience less response overlap in the choice of responses for the task.

In addition, the relationship between anterior cingulate cortex and attention maintenance control is supported. According to Rueda and colleagues, the anterior cingulate cortex is a kind of "control rod" that allows the attention system to be arbitrary [40]. A group to define the relationship between anterior cingulate cortex and lateral prefrontal cortex during direct attention tasks showed that the anterior cingulate cortex takes place during tasks requiring continuous attention control and performance monitoring [41]. Another study examined the reciprocal relationship between emotional control and effort; hence, the anterior cingulate cortex has a proximity to emotional processing regions. Accordingly, the anterior cingulate cortex is associated with the cognitive evaluation of distressing photographs, thereby reduc-

Executive Functions and Neurology in Children and Adolescents

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37

Temporal and parietal cortexes are also important components of the executive net at the same time. Both temporal cortex and parietal cortex are associated with inhibitory control, set shifting, initiation, goal-directed behavior, and working memory (**Figure 5**). The upper parietal cortex plays a primary role in task change, regardless of whether the task involves verbal, visual, or spatial knowledge or not. Other areas of the parietal cortex are primarily responsible for initiating and completing targeted activities. It appears that the parietal cortex regions are also involved in updating the working memory. Especially, the upper left parietal

The cerebellum is a major but often a less well-understood component of the executive functions system. Cerebellum reaches its size at about 11 years for girls and 15 years for boys and is as important as regions that control executive function in early childhood [44]. Cerebellum gains maturity during motor control, emotional processing, and adolescence period and plays a central role in high cognitive functions. The cortico-ponto-cerebellar network works intensively in the timing and ordering of requests such as verbal working memory and executive aspects of visual and verbal analysis (**Figure 6**) [45]. In addition, it is also known

ing the negative effect [42].

**2.3. Parietal and temporal cortexes**

**2.4. Executive functions and cerebellum**

**Figure 5.** Prefrontal cortex and parietal cortex.

region is linked to the current tasks of ongoing activity [43].

The prefrontal cortex is also associated with multitasking ability. The prefrontal cortex plays a role in the ability to hold knowledge as well. This feature is unique, prefrontal cortex neurons do not interrupt firing against a new stimulus [36]. This response pattern is useful in terms of showing maturity when individuals are forced to interfere independently with an increasingly complex and changing environment. Blakemore and Choudhury suggest that adult's multitasking skills are better than children or adolescents. Adolescents (aged 11–14) and children (aged 6–10) completed a number of tasks related to prospective memory with an adult group (mean age 25); results showed that adults use more effective strategies than adolescents or children. Thus, the prefrontal cortex also allows us to recall our daily life and the necessary information to achieve its mission despite disturbing stimuli [37].

### **2.2. Executive functions and limbic system**

Regarding executive functions, the limbic system and prefrontal cortex, especially the anterior cingulate cortex are related to emotional regulation and processing, impulse control, and directing attention (**Figure 4**). An error monitoring task study on early adolescence, late adolescence, and adult performance revealed that the error rates were 11% in young adolescents, 7% in late adolescence, and in adulthood, it was even lower [38]. Potential related to the events during the mission localized on the anterior cingulate cortex or on its surroundings, which suggests that the difference in age-related task performance may be due to the maturation of the anterior cingulate cortex. Adults with good performance in an impulse control task were found to have larger anterior cingulate cortexes on magnetic resonance imaging (MRI) [39].

**Figure 4.** ACC with limbic system.

In addition, the relationship between anterior cingulate cortex and attention maintenance control is supported. According to Rueda and colleagues, the anterior cingulate cortex is a kind of "control rod" that allows the attention system to be arbitrary [40]. A group to define the relationship between anterior cingulate cortex and lateral prefrontal cortex during direct attention tasks showed that the anterior cingulate cortex takes place during tasks requiring continuous attention control and performance monitoring [41]. Another study examined the reciprocal relationship between emotional control and effort; hence, the anterior cingulate cortex has a proximity to emotional processing regions. Accordingly, the anterior cingulate cortex is associated with the cognitive evaluation of distressing photographs, thereby reducing the negative effect [42].
