title: Modeling discoordination of cortical neuroactivity: relevance for the executive control of attention in Alzheimer's disease.
abstract: Executive deficits due to Alzheimer's disease (AD) seriously compromise patients' ability for concurrent manipulation of information. Understanding such deficits must integrate neurophysiological findings, results from dual-task experiments and successful psychological models of the matching of ascending and descending information to direct attention. We considered attention as dependent on an oscillatory matching between what is looked for and what is perceived. Hence we implemented a model of coordination between oscillatory neuroactivity of interconnected cortical units. We simulated executive deficits evident during dual-tasks as a breakdown of intercortical oscillatory coordination. We investigated the hypothesis that this breakdown is due to functional disconnection between cortical areas, by measuring the effect of interfering tasks in 'control' and 'lesioned' models. 'Control' models successfully reproduced many features of attention. Several neuropathological mechanisms in AD were found likely to cause functional disconnection. Functional disconnection resulted in much greater impairment of coordination during dual rather than single tasks. This could account for key neuropsychological data from the literature. Executive deficits in AD may thus be partly explained by oscillatory discoordination. Oscillatory coordination phenomena are likely to reflect large scale network interactions in the brain that are concerned with integrative function beyond the specific example considered in this study.
authors.affiliation: Department of Psychiatry and Behavioural Sciences, University College London, Wolfson Building, 48 Riding House Str., London W1N 8AA, England. fzsemmo@gn.apc.org
authors.forename: Michael
authors.initials: M
authors.lastname: Moutoussis
authors.forename: Martin W
authors.initials: MW
authors.lastname: Orrell
authors.forename: Robin
authors.initials: R
authors.lastname: Morris
mesh_terms: D000544:Alzheimer Disease / Q000503:physiopathology*; D001288:Attention / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D006801:Humans; D008959:Models, Neurological; D009483:Neuropsychological Tests; D011597:Psychomotor Performance; D011930:Reaction Time