title: Directed and divided attention in Alzheimer's disease: impairment in shifting of attention to global and local stimuli.
abstract: This study investigated the relative performance of Alzheimer's disease (AD) patients and normal controls on directed and divided attention reaction time (RT) tasks that involved the use of global-local stimuli (e.g., a large '1' made from small '2s'). Relative to normals, AD patients displayed disproportionately greater impairment on the divided attention task compared to the directed attention task. On the divided attention task, when the target remained at the same global-local level across consecutive trials, the AD patients displayed a greater facilitation effect than did the controls when responding to the second stimulus. However, when the target changed levels across consecutive trials (i.e., from the global to the local, or vice versa) the AD patients' RTs to the second stimulus were disproportionately slower than were the controls' RTs. These results demonstrated that AD patients are impaired in disengaging and shifting attention across levels of perceptual organization within the same stimulus.
authors.affiliation: San Diego School of Medicine.
authors.forename: J V
authors.initials: JV
authors.lastname: Filoteo
authors.forename: D C
authors.initials: DC
authors.lastname: Delis
authors.forename: P J
authors.initials: PJ
authors.lastname: Massman
authors.forename: T
authors.initials: T
authors.lastname: Demadura
authors.forename: N
authors.initials: N
authors.lastname: Butters
authors.forename: D P
authors.initials: DP
authors.lastname: Salmon
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000523:psychology; D001288:Attention; D004193:Discrimination Learning; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D009949:Orientation; D010364:Pattern Recognition, Visual; D012858:Size Perception