executive dysfunction executive dysfunction in psychology and neuroscience, executive dysfunction, or executive function deficit, is a disruption to the efficacy of the executive functions, which is a group of cognitive processes that regulate, control, and manage other cognitive processes. executive dysfunction can refer to both neurocognitive deficits and behavioural symptoms. it is implicated in numerous psychopathologies and mental disorders, as well as short-term and long-term changes in non-clinical executive control. overview 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. 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. 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. impairments in set shifting ability are a notable feature of executive dysfunction; set shifting is the cognitive ability to dynamically change focus between points of fixation based on changing goals and environmental stimuli. this offers a parsimonious explanation for the common occurrence of impulsive, hyperactive, disorganized, and aggressive behaviour in clinical patients with executive dysfunction. a recent 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. other common and distinctive symptoms of executive dysfunction include utilization behaviour, which is compulsive manipulation/use of nearby objects due simply to their presence and accessibility (rather than a functional reason); and imitation behaviour, a tendency to rely on imitation as a primary means of social interaction. 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. more recent research confirms 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 attention-deficit/hyperactivity disorder is a classification given to a set of subjectively-determined symptoms implicating executive dysfunction – current models indicate that such clinical symptoms are caused by executive dysfunction. neurophysiology as previously mentioned, executive functioning is not a unitary concept. 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. a common assumption is that disrupted executive control processes are associated with pathology in prefrontal brain regions. 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. neuroimaging with pet and fmri has confirmed the relationship between executive function and functional frontal pathology. neuroimaging studies have also suggested that some constituent functions are not discretely localized in prefrontal regions. 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 and appear to be the genuine result of basal ganglia damage. with substantial cognitive load, fmri signals indicate a common network of frontal, parietal and occipital cortices, thalamus, and the cerebellum. this observation suggests that executive function is mediated by dynamic and flexible networks that are characterized using functional integration and effective connectivity analyses. the complete circuit underlying executive function includes both a direct and an indirect circuit. the neural circuit responsible for executive functioning is, in fact, located primarily in the frontal lobe. this main circuit originates in the dorsolateral prefrontal cortex/orbitofrontal cortex and then projects through the striatum and thalamus to return to the prefrontal cortex. not surprisingly, plaques and tangles in the frontal cortex can cause disruption in functions as well as damage to the connections between prefrontal cortex and the hippocampus. another important point is in the finding that structural mri images link the severity of white matter lesions to deficits in cognition. the emerging view suggests that cognitive processes materialize from networks that span multiple cortical sites with closely collaborative and over-lapping functions. 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. genetics certain genes have been identified with a clear correlation to executive dysfunction and related psychopathologies. according to friedman et al. (2008), 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. 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. memory, concentration, initiation, energy, mental clarity and indecision are all measures that are scored during this activity. those with deficits in executive functioning will often make errors on the first clock but not the second. in other words, they will be unable to generate their own example, but will show proficiency in the copying task. stroop task the cognitive mechanism involved in the stroop task is referred to as directed attention. 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. 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. more modern variations of the stroop task tend to be more difficult and often try to limit the sensitivity of the test. wisconsin card sorting test 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. these abilities are primarily determined by the frontal lobes and basal ganglia, which are crucial components of executive functioning; making the wcst a good measure for this purpose. the wcst utilizes a deck of 128 cards that contains four stimulus cards. the figures on the cards differ with respect to color, quantity, and shape. the participants are then given a pile of additional cards and are asked to match each one to one of the previous cards. typically, children between ages 9 and 11 are able to show the cognitive flexibility that is needed for this test. 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