Executive dysfunction

Executive functioning is a theoretical construct representing a domain of cognitive processes that regulate, control, and manage other cognitive processes. Executive functioning is not a unitary concept; it is a broad description of the set of processes involved in certain areas of cognitive and behavioural control. Deficits of the executive functions are observed in all populations to varying degrees, but severe executive dysfunction can have devastating effects on cognition and behaviour in both individual and social contexts on a day-to-day basis. Executive dysfunction does occur to a minor degree in all individuals on both short-term and long-term scales. In non-clinical populations, the activation of executive processes appears to inhibit further activation of the same processes, suggesting a mechanism for normal fluctuations in executive control. Decline in executive functioning is also associated with both normal and clinical aging. The decline of memory processes as people age appears to affect executive functions, which also points to the general role of memory in executive functioning. Executive dysfunction appears to consistently involve disruptions in task-oriented behavior, which requires executive control in the inhibition of habitual responses and goal activation. Such executive control is responsible for adjusting behaviour to reconcile environmental changes with goals for effective behaviour. This offers a parsimonious explanation for the common occurrence of impulsive, hyperactive, disorganized, and aggressive behaviour in clinical patients with executive dysfunction. A 2011 study confirms there is a lack of self-control, greater impulsivity, and greater disorganization with executive dysfunction, leading to greater amounts of aggressive behavior. 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. Russell Barkley proposed a hybrid model of the role of behavioural disinhibition in the presentation of ADHD, which has served as the basis for much research of both ADHD and broader implications of the executive system. Research also suggests that executive set shifting is a co-mediator with episodic memory of feeling-of-knowing (FOK) accuracy, such that executive dysfunction may reduce FOK accuracy. There is some evidence suggesting that executive dysfunction may produce beneficial effects as well as maladaptive ones. Abraham et al. demonstrate that creative thinking in schizophrenia is mediated by executive dysfunction, and they establish a firm etiology for creativity in psychoticism, pinpointing a cognitive preference for broader top-down associative thinking versus goal-oriented thinking, which closely resembles aspects of ADHD. It is postulated that elements of psychosis are present in both ADHD and schizophrenia/schizotypy due to dopamine overlap. == Cause ==

The cause of executive dysfunction is heterogeneous, as many neurocognitive processes are involved in the executive system and each may be compromised by a range of genetic and environmental factors. Learning and development of long-term memory play a role in the severity of executive dysfunction through dynamic interaction with neurological characteristics. Studies in cognitive neuroscience suggest that executive functions are widely distributed throughout the brain, though a few areas have been isolated as primary contributors. Executive dysfunction is studied extensively in clinical neuropsychology as well, allowing correlations to be drawn between such dysexecutive symptoms and their neurological correlates. A 2015 study confirmed that executive dysfunction has a positive correlation with neurodevelopmental disorders such as autism spectrum disorder (ASD) or attention deficit hyperactivity disorder (ADHD). Executive processes are closely integrated with memory retrieval capabilities for overall cognitive control; in particular, goal/task-information is stored in both short-term and long-term memory, and effective performance requires effective storage and retrieval of this information. Executive dysfunction characterizes many of the symptoms observed in numerous clinical populations. In the case of acquired brain injury and neurodegenerative diseases there is a clear neurological etiology producing dysexecutive symptoms. Conversely, syndromes and disorders are defined and diagnosed based on their symptomatology rather than etiology. Thus, while Parkinson's disease, a neurodegenerative condition, causes executive dysfunction, a disorder such as ADHD is a classification given to a set of subjectively-determined symptoms implicating executive dysfunction – models from the 1990s and 2000s indicate that such clinical symptoms are caused by executive dysfunction. This is supported to some extent by the primary literature, which shows both pre-frontal activation and communication between the pre-frontal cortex and other areas associated with executive functions such as the basal ganglia and cerebellum. In most cases of executive dysfunction, deficits are attributed to either frontal lobe damage or dysfunction, or to disruption in fronto-subcortical connectivity. Functional imaging studies using different tests of executive function have implicated the dorsolateral prefrontal cortex to be the primary site of cortical activation during these tasks. In addition, PET studies of patients with Parkinson's disease have suggested that tests of executive function are associated with abnormal function in the globus pallidus This observation suggests that executive function is mediated by dynamic and flexible networks that are characterized using functional integration and effective connectivity analyses. The emerging view suggests that cognitive processes materialize from networks that span multiple cortical sites with closely collaborative and over-lapping functions. the heritability of executive functions is among the highest of any psychological trait. 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. 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) and the experience of reward, which are major aspects of executive functioning. COMT is also linked to methylphenidate (stimulant medication) response in children with ADHD. Both the DRD4/7R and COMT/Val158Met polymorphisms are also correlated with executive dysfunction in schizophrenia and schizotypal behaviour. Evolutionary perspective The prefrontal lobe controls two related executive functioning domains. The first is mediation of abilities involved in planning, problem solving, and understanding information, as well as engaging in working memory processes and controlled attention. In this sense, the prefrontal lobe is involved with dealing with basic, everyday situations, especially those involving metacognitive functions. The second domain involves the ability to fulfill biological needs through the coordination of cognition and emotions which are both associated with the frontal and prefrontal areas. The prefrontal lobe in humans has been associated both with metacognitive executive functions and emotional executive functions. Theory and evidence suggest that the frontal lobes in other primates also mediate and regulate emotion, but do not demonstrate the metacognitive abilities that are demonstrated in humans. This uniqueness of the executive system to humans implies that there was also something unique about the environment of ancestral humans, which gave rise to the need for executive functions as adaptations to that environment. 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. 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. 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. 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. == Testing and measurement ==

There are several measures that can be employed to assess the executive functioning capabilities of an individual. Although a trained non-professional working outside of an institutionalized setting can legally and competently perform many of these measures, a trained professional administering the test in a standardized setting will yield the most accurate results. Clock drawing test The clock drawing test (CDT) is a brief cognitive task that can be used by physicians who suspect neurological dysfunction based on history and physical examination. It is relatively easy to train non-professional staff to administer a CDT. Therefore, this is a test that can easily be administered in educational and geriatric settings and can be utilized as a precursory measure to indicate the likelihood of further/future deficits. Also, generational, educational and cultural differences are not perceived as impacting the utility of the CDT. The procedure of the CDT begins with the instruction to the participant to draw a clock reading a specific time (generally 11:10). After the task is complete, the test administrator draws a clock with the hands set at the same specific time. Then the patient is asked to copy the image. Errors in clock drawing are classified according to the following categories: omissions, perseverations, rotations, misplacements, distortions, substitutions and additions. Those with deficits in executive functioning will often make errors on the first clock but not the second. The stimulus is a colour word that is printed in a different colour than what the written word reads. For example, the word "red" is written in a blue font. One must verbally classify the colour that the word is displayed/printed in, while ignoring the information provided by the written word. In the aforementioned example, this would require the participant to say "blue" when presented with the stimulus. Although the majority of people will show some slowing when given incompatible text versus font colour, this is more severe in individuals with deficits in inhibition. The Stroop task takes advantage of the fact that most humans are so proficient at reading colour words that it is extremely difficult to ignore this information, and instead acknowledge, recognize and say the colour the word is printed in. The Stroop task is an assessment of attentional vitality and flexibility. Trail-making test Another prominent test of executive dysfunction is known as the Trail-making test. This test is composed of two main parts (Part A & Part B). Part B differs from Part A specifically in that it assesses more complex factors of motor control and perception. Part B of the Trail-making test consists of multiple circles containing letters (A-L) and numbers (1-12). The participant's objective for this test is to connect the circles in order, alternating between number and letter (e.g. 1-A-2-B) from start to finish. The participant is required not to lift their pencil from the page. The task is also timed as a means of assessing speed of processing. Set-switching tasks in Part B have low motor and perceptual selection demands, and therefore provide a clearer index of executive function. making the WCST a good measure for this purpose. The WCST utilizes a deck of 128 cards that contains four stimulus cards. == In clinical populations ==

The executive system's broad range of functions relies on, and is instrumental in, a broad range of neurocognitive processes. 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. As a result, executive dysfunction is implicated etiologically or co-morbidly in many psychiatric illnesses, which often show the same symptoms as dysexecutive syndrome. It has been assessed and researched extensively in relation to cognitive developmental disorders, psychotic disorders, mood disorders, and conduct disorder, as well as neurodegenerative diseases and acquired brain injury (ABI). Environmental dependency syndrome is a dysexecutive syndrome marked by significant behavioural dependence on environmental cues and is marked by excessive imitation and utilization behaviour. It has been observed in patients with a variety of etiologies including ABI, exposure to phendimetrazine tartrate, stroke, and various frontal lobe lesions. In both children and adults with ADHD, an underlying executive dysfunction involving the prefrontal regions and other interconnected subcortical structures has been found. Also, a more central impairment in self-regulation is noted in cases of ADHD. This being both a physical and psychological disorder has reinforced that obese individuals with ADHD need more treatment time (with associated costs), and are at a higher risk of developing physical and emotional complications. However, impaired performance was measured on psychometric measures assumed to assess higher order executive function. Working memory and multi-tasking impairments typically characterize the disorder. Patients often demonstrate noticeable deficits in the central executive component of working memory as conceptualized by Baddeley and Hitch. However, performance on tasks associated with the phonological loop and visuospatial sketchpad are typically less affected. More specifically, patients with schizophrenia show impairment to the central executive component of working memory, specific to tasks in which the visuospatial system is required for central executive control. • Fluency. Fluency refers to the ability to generate novel ideas and responses. Although adult populations are largely underrepresented in this area of research, findings have suggested that autistic children generate fewer novel words and ideas and produce less complex responses than matched controls. • Planning. Planning refers to a complex, dynamic process, wherein a sequence of planned actions must be developed, monitored, re-evaluated and updated. Autistic persons demonstrate impairment on tasks requiring planning abilities relative to typically functioning controls, with this impairment maintained over time. As might be suspected, in the case of autism comorbid with learning disability, an additive deficit is observed in many cases. • Flexibility. Poor mental flexibility, as demonstrated in autistic individuals, is characterized by perseverative, stereotyped behaviour, and deficits in both the regulation and modulation of motor acts. Some research has suggested that autistic individuals experience a sort of 'stuck-in-set' perseveration that is specific to the disorder, rather than a more global perseveration tendency. These deficits have been exhibited in cross-cultural samples and have been shown to persist over time. Autistic individuals have also been shown to react slower as well as perform slower in tasks that require mental flexibility when compared to their non-autistic peers. Although there has been some debate, inhibition is generally no longer considered to be an executive function deficit in autistic people. Moreover, these cognitive deficits appear to be consistent cross-culturally, In contrast to the more generalized cognitive impairment demonstrated in persons with schizophrenia, for example, deficits in bipolar disorder are typically less severe and more restricted. It has been suggested that a "stable dys-regulation of prefrontal function or the subcortical-frontal circuitry [of the brain] may underlie the cognitive disturbances of bipolar disorder". Executive dysfunction in bipolar disorder is suggested to be associated particularly with the manic state, and is largely accounted for in terms of the formal thought disorder that is a feature of mania. Persons affected by PD often demonstrate difficulties in working memory, a component of executive functioning. Cognitive deficits found in early PD process appear to involve primarily the fronto-executive functions. Moreover, studies of the role of dopamine in the cognition of PD patients have suggested that PD patients with inadequate dopamine supplementation are more impaired in their performance on measures of executive functioning. This suggests that dopamine may contribute to executive control processes. Increased distractibility, problems in set formation and maintaining and shifting attentional sets, deficits in executive functions such as self-directed planning, problems solving, and working memory have been reported in PD patients. Similarly, they often have trouble remembering the locations of objects that they have recently seen, and thus also have trouble with encoding this information into long-term memory. ;Central executive aspects: PD is often characterized by a difficulty in regulating and controlling one's stream of thought, and how memories are utilized in guiding future behaviour. Also, persons affected by PD often demonstrate perseverative behaviours such as continuing to pursue a goal after it is completed, or an inability to adopt a new strategy that may be more appropriate in achieving a goal. However, some research from 2007 suggests that PD patients may actually be less persistent in pursuing goals than typical persons and may abandon tasks sooner when they encounter problems of a higher level of difficulty. ;Locating events in time: PD patients often demonstrate deficits in their ability to sequence information, or date events. Part of the problems is hypothesized to be due to a more fundamental difficulty in coordinating or planning retrieval strategies, rather than failure at the level of encoding or storing information in memory. This deficit is also likely to be due to an underlying difficulty in properly retrieving script information. PD patients often exhibit signs of irrelevant intrusions, incorrect ordering of events, and omission of minor components in their script retrieval, leading to disorganized and inappropriate application of script information. == Treatment ==

Medication Methylphenidate- and amphetamine-based medications are first-line treatments for ADHD. On average, these stimulants are more effective at treating core ADHD symptoms including executive dysfunction than psychosocial treatment alone. or norepinephrine reuptake inhibitor reduces core ADHD symptoms equally well with or without psychosocial treatment. However, psychosocial treatment may confer other benefits. One kind of psychosocial treatment has been found to be particularly helpful, Behavioral Parent Training (BPT). Behavioral Parent Training (BPT) helps parents learn, through the help of a trained mental health professional, how to help their child behave better. This outlines proper use of reward and punishment with the child, mostly using methods of positive and negative reinforcement rather than punishment. For example, taking away a positive reinforcement such as praise, as opposed to adding a punishment. Psychosocial treatments are effective for adults with attention-deficit/hyperactivity disorder (ADHD) as well. One study shows that there are a number of useful psychosocial interventions that help adults with ADHD live better lives too. These included mindfulness training, cognitive based behavioral therapy, as well as education to help the participants recognize problem behaviors in their lives. Cognitive behavioral therapy and group rehabilitation Cognitive behavioral therapy (CBT) is a frequently suggested treatment for executive dysfunction, but has shown limited effectiveness. However, a study of CBT in a group rehabilitation setting showed a significant increase in positive treatment outcome compared with individual therapy. Patients' self-reported symptoms on 16 different ADHD/executive-related items were reduced following the treatment period. Treatment for patients with acquired brain injury The use of auditory stimuli has been examined in the treatment of dysexecutive syndrome. The presentation of auditory stimuli causes an interruption in current activity, which appears to aid in preventing "goal neglect" by increasing the patients' ability to monitor time and focus on goals. Given such stimuli, subjects no longer performed below their age group average IQ. Patients with acquired brain injury have also been exposed to goal management training (GMT). GMT skills are associated with paper-and-pencil tasks that are suitable for patients having difficulty setting goals. From these studies there has been support for the effectiveness of GMT and the treatment of executive dysfunction due to ABI. == Developmental context ==

An understanding of how executive dysfunction shapes development has implications how we conceptualize executive functions and their role in shaping the individual. Disorders affecting children such as ADHD, along with oppositional defiant disorder, conduct disorder, high functioning autism, and Tourette's syndrome have all been suggested to involve executive functioning deficits. The main focus of research in 2000s had been on working memory, planning, set shifting, inhibition, and fluency. This research suggests that differences exist between typically functioning, matched controls, and clinical groups, on measures of executive functioning. One study required children to perform a task from a series of psychological tests, with their performance used as a measure of executive function. The exact distinction between parenting style and the importance of family structure on child development is still somewhat unclear. However, in infancy and early childhood, parenting is among the most critical external influences on child reactivity. In Mahoney's study of maternal communication, results indicated that the way mothers interacted with their children accounted for almost 25% of variability in children's rate of development. Every child is unique, making parenting an emotional challenge that should be most closely related to the child's level of emotional self-regulation (persistence, frustration and compliance). Based on the principle of "active learning", responsive teaching is a method that was being applauded in 1980s as adaptable for individual caregivers, children and their combined needs The effect of parenting styles on the development of children is an important area of research that seems to be forever ongoing and altering. == Comorbidity ==

Flexibility problems are more likely to be related to anxiety, and metacognition problems are more likely to be related to depression. == Socio-cultural implications ==

Education In the classroom environment, children with executive dysfunction typically demonstrate skill deficits that can be categorized into two broad domains: a) self-regulatory skills; and b) goal-oriented skills. The table below is an adaptation of McDougall's Ultimately, executive function difficulties should not be attributed to negative personality traits or characteristics (e.g. laziness, lack of motivation, apathy, and stubbornness) as these attributions are neither useful nor accurate. Several factors should be considered in the development of intervention strategies. These include, but are not limited to: developmental level of the child, comorbid disabilities, environmental changes, motivating factors, and coaching strategies. This can hinder their attention for lectures, readings, and completing assignments. Individuals with this disorder have also been found to require more stimuli for information processing in reading and writing. Also, these individuals can be found to repeat words or phrases consistently either immediately after they are learned or after a delayed period of time. The prefrontal cortex is involved with mental functions including; effective range of emotions, forethought, and self-control. In a 2008 study conducted by Barbosa & Monteiro, it was discovered that the recurrent criminals that were considered in this study had executive dysfunction. The uncontrollable deficiency of executive function has an increased expectancy for aggressive behavior that can result in a criminal deed. Orbitofrontal injury also hinders the ability to be risk avoidant, make social judgments, and may cause reflexive aggression. A common retort to these findings is that the higher incidence of cerebral lesions among the criminal population may be due to the peril associated with a life of crime. Along with this reasoning, it would be assumed that some other personality trait is responsible for the disregard of social acceptability and reduction in social aptitude. Furthermore, some think the dysfunction cannot be entirely to blame. There are interacting environmental factors that also have an influence on the likelihood of criminal action. 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. One must recognize that the frustrations of life, combined with a limited ability to control life events, can easily cause aggression and/or other criminal activities. == See also ==