Invited Symposium: What Can Genetic Models Tell Us About Attention-Deficit Hyperactivity Disorder (ADHD)?
Attention Deficit/ Hyperactivity Disorder (ADHD) is a childhood psychiatric disorder which went carefully defined, affects around 1% of the childhood population (Swanson et al., 1998). The primary symptoms: distractibility, impulsivity and overactivity vary in degree and association in such children, which led DSM IV to propose three subgroups. Only one of these subgroups, the combined subtype: deficits in all three areas, meets the ICD-10 criteria. Since the other two subtypes are used extensively in North America (but not in Europe), widely different results between centers are to be expected and have been reported. Central to the ADHD syndrome is the idea of an attention deficit. In order to investigate attention, it is necessary to define what one means by this term and to operationalise it in such a manner that others can test and replicate findings. We have advocated the use of a cognitive-energetic model (Sanders, 1983). The cognitive-energetic model of ADHD approaches the ADHD deficiency at three distinct levels. First, a lower set of cognitive processes: encoding, central processing and response organisation are postulated. Study of these processes has indicated that there are no deficits of processing at encoding or central processing but are present in motor organization (see for Review Sergeant & van der Meere, 1990). A second level of the cognitive-energetic model consists of the energetic pools: arousal, activation and effort. At this level, the primary deficits of ADHD are associated with the activation pool and (to some extent) effort. The third level of the model contains a management or executive function system. Barkley (1997) reviewed the literature and concluded that executive function deficiencies were primarily due to a failure of inhibition. Oosterlaan, Logan & Sergeant (1998) demonstrated that this explanation was not specific to ADHD but also applied to children with the associated disorders of oppositional defiant and conduct disorder. Other executive functions seem to be intact, while others, are deficient. It will be argued here that the cognitive-energetic model is a useful guide to determining not only ADHD deficiencies and associated disorders but also linking, on the one hand, human cognitive neuroscience studies with, on the other hand, neurobiological models of ADHD using animals (Saddile et al, 1998; Papa et al 1998). A plea will be made for an integrated attack on this research problem and the suggestion offered that conceptual refinement between levels of analysis is essential for further fundamental work to succeed.
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|Sergeant, J.; (1998). Cognitive-energetic Model of Attention Deficit Hyperactivity Disorder. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/sadile/sergeant0228/index.html|
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