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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.〔Elliott R (2003). Executive functions and their disorders. British Medical Bulletin. (65); 49–59〕 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. Executive dysfunction is not the same as dysexecutive syndrome, a term coined by Alan Baddeley to describe a common pattern of dysfunction in executive functions, such as deficiencies in planning, abstract thinking, flexibility and behavioural control.〔Wilson, B.A., Evans, J.J., Emslie, H., Alderman, N., & Burgess, P. (1998). The development of an ecologically valid test for assessing patients with a dysexecutive syndrome. ''Neuropsychological Rehabilitation, 8'', 213-228.〕〔Baddeley, A., & Wilson, B. (1988). Frontal amnesia and the dysexecutive syndrome. ''Brain and Cognition, 7'', 212-230.〕 This group of symptoms, usually resulting from brain damage, tend to occur together.〔Halligan, P.W., Kischka, U., & Marshall, J.C. (2004). ''Handbook of clinical neuropsychology.'' Oxford University Press.〕 However, the existence of dysexecutive syndrome is controversial.〔Stuss, D.T. & Alexander, M.P. (2007). Is there a dysexecutive syndrome? ''Philosophical transactions of the Royal Society of London. Series B, Biological Sciences, 362'' (1481), 901-15.〕 == 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.〔Elliott R (2003). Executive functions and their disorders. British Medical Bulletin. (65); 49–59〕 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.〔Jurado MB, Rosselli M (2007). The elusive nature of executive functions: a review of our current understanding. Neuropsychol Rev, 17(3):213–33.〕 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. 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.〔Schmeichel, BJ (2007). Attention Control, memory updating, and emotion regulation temporarily reduce the capacity for executive control. Journal of Experimental Psychology: General, 136(2):241–55〕 Decline in executive functioning is also associated with both normal and clinical aging.〔Zelazo PD, Craik FI, Booth L (2004). Executive function across the life span. Acta Psychol (Amst), 115 (2–3):167–83.〕 In aging populations, the decline of memory processes appears to affect executive functions, which also points to the general role of memory in executive functioning.〔Bisiacchi PS, Borella E, Bergamaschi S, Carretti B, Mondini S (2008). Interplay between memory and executive functions in normal and pathological aging. J Clin Exp Neuropsychol, 30(6):723–33.〕 Executive dysfunction appears to consistently involve disruptions in task-oriented behavior, which requires executive control in the inhibition of habitual responses and goal activation.〔Nieuwenhuis S, Broerse A, Nielen MM, de Jong R (2004). A goal activation approach to the study of executive function: an application to antisaccade tasks. Brain Cogn. 56(2):198–214. Review.〕 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.〔Avila C, Barros A, Ortet G, Parcet MA & Ibanez M I (2003). Set-shifting and sensitivity to reward: A possible dopamine mechanism for explaining disinhibitory disorders. Cognition and Emotion, 17, 951–59.〕 This offers a parsimonious explanation for the common occurrence of impulsive, hyperactive, disorganized, and aggressive behaviour in clinical patients with executive dysfunction. 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.〔Schmeichel BJ, Volokhov RN & Demaree HA (2008). Working memory capacity and the Self-Regulation of Emotional Expression and Experience" ''Journal of Personality and Social Psychology'' 95(6), 1526–40.〕 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.〔Hoffmann MW, & Bill PLA (1992). The environmental dependency syndrome, imitation behaviour and utilization behaviour as presenting symptoms of bilateral frontal lobe infarction due to moyamoya disease. South African medical journal, 81(5): 271–73〕 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.〔Perrotin A, Tournell L, Isingrini M (2008). Executive functioning and memory as potential mediators of the episodic feeling-of-knowing accuracy" ''Brain and Cognition'' 67:76–87.〕 There is some evidence suggesting that executive dysfunction may produce beneficial effects as well as maladaptive ones. Abraham et al.〔Abraham A, Windmann S, McKenna P, Güntürkün O (2007). Creative thinking in schizophrenia: the role of executive dysfunction and symptom severity. Cognitive Neuropsychiatry, 12(3), 235–58.〕 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.〔Keshavan MS, Sujata M, Mehra A, Montrose DM, Sweeney JA (2003). Psychosis proneness and ADHD in young relatives of schizophrenia patients. Schizophrenia Research, 59(1), 85–92.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Executive dysfunction」の詳細全文を読む スポンサード リンク
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