Executive dysfunction is the mechanism underlying ADHD paralysis,[2] and in a broader context, it can encompass other cognitive difficulties like planning, organizing, initiating tasks and regulating emotions.
[1] Executive processes are integral to higher brain function, particularly in the areas of goal formation, planning, goal-directed action, self-monitoring, attention, response inhibition, and coordination of complex cognition and motor control for effective performance.
[11] This offers a parsimonious explanation for the common occurrence of impulsive, hyperactive, disorganized, and aggressive behaviour in clinical patients with executive dysfunction.
[12] Executive dysfunction, particularly in working memory capacity, may also lead to varying degrees of emotional dysregulation, which can manifest as chronic depression, anxiety, or hyperemotionality.
[1] Many studies have been conducted in an attempt to pinpoint the exact regions of the brain that lead to executive dysfunction, producing a vast amount of often conflicting information indicating wide and inconsistent distribution of such functions.
[26] The emerging view suggests that cognitive processes materialize from networks that span multiple cortical sites with closely collaborative and over-lapping functions.
[23] A challenge for future research will be to map the multiple brain regions that might combine with each other in a vast number of ways, depending on the task requirements.
The dopamine receptor D4 gene (DRD4) with 7'-repeating polymorphism (7R) has been repeatedly shown to correlate strongly with impulsive response style on psychological tests of executive dysfunction, particularly in clinical ADHD.
[28] The catechol-o-methyl transferase gene (COMT) codes for an enzyme that degrades catecholamine neurotransmitters (DA and NE), and its Val158Met polymorphism is linked with the modulation of task-oriented cognition and behavior (including set shifting[29]) and the experience of reward, which are major aspects of executive functioning.
[33] Some examples of possible adaptive problems that would have been solved by the evolution of an executive system are: social exchange, imitation and observational learning, enhanced pedagogical understanding, tool construction and use, and effective communication.
[33] In a similar vein, some have argued that the unique metacognitive capabilities demonstrated by humans have arisen out of the development of a sophisticated language (symbolization) systems and culture.
[32] Moreover, in a developmental context, it has been proposed that each executive function capability originated as a form of public behaviour directed at the external environment, but then became self-directed, and then finally, became private to the individual, over the course of the development of self-regulation.
[33] These shifts in function illustrate the evolutionarily salient strategy of maximizing longer-term social consequences over near-term ones, through the development of an internal control of behaviour.
The Stroop task requires the participant to engage in and allows assessment of processes such as attention management, speed and accuracy of reading words and colours and of inhibition of competing stimuli.
[44] The Wisconsin Card Sorting Test (WCST) is used to determine an individual's competence in abstract reasoning, and the ability to change problem-solving strategies when needed.
[39] These abilities are primarily determined by the frontal lobes and basal ganglia, which are crucial components of executive functioning;[45] making the WCST a good measure for this purpose.
Clinical presentation of severe executive dysfunction that is unrelated to a specific disease or disorder is classified as a dysexecutive syndrome, and often appears following damage to the frontal lobes of the cerebral cortex.
[51] Although the etiology is not completely understood, it is closely related to dopaminergic activity and is strongly associated with both neurocognitive and genetic elements of executive dysfunction.
[14] However, some research has suggested the possibility that the severity of executive dysfunction in individuals with ADHD declines with age as they learn to compensate for the aforementioned deficits.
Although ADHD has typically been conceptualized in a categorical diagnostic paradigm, it has also been proposed that this disorder should be considered within a more dimensional behavioural model that links executive functions to observed deficits.
[56] Proponents argue that classic conceptions of ADHD falsely localize the problem at perception (input) rather than focusing on the inner processes involved in producing appropriate behaviour (output).
[56] Moreover, others have theorized that the appropriate development of inhibition (something that is seen to be lacking in individuals with ADHD) is essential for the normal performance of other neuropsychological abilities such as working memory, and emotional self-regulation.
[64] Moreover, these cognitive deficits appear to be consistent cross-culturally,[64] indicating that these impairments are characteristic of the disorder and not attributable to differences in cultural values, norms, or practice.
Parkinson's disease (PD) primarily involves damage to subcortical brain structures and is usually associated with movement difficulties, in addition to problems with memory and thought processes.
However, a study of CBT in a group rehabilitation setting showed a significant increase in positive treatment outcome compared with individual therapy.
[82] The tests included assessments of: executive functions (self-regulation, monitoring, attention, flexibility in thinking), language, sensorimotor, visuospatial, and learning, in addition to social perception.
Responsive teaching is an early intervention curriculum designed to address the cognitive, language, and social needs of young children with developmental problems.
[89] The table below is an adaptation of McDougall's[89] summary and provides an overview of specific executive function deficits that are commonly observed in a classroom environment.
[93] In view of the fact that abnormalities in executive function can limit how people respond to rehabilitation and re-socialization programs[93] these findings of the recurrent criminals are justified.
This theory proposes that individuals with this deficit are less able to control impulses or foresee the consequences of actions that seem attractive at the time (see above) and are also typically provoked by environmental factors.