title: Where attention falls: Increased risk of falls from the converging impact of cortical cholinergic and midbrain dopamine loss on striatal function.
abstract: Falls are a major source of hospitalization, long-term institutionalization, and death in older adults and patients with Parkinson's disease (PD). Limited attentional resources are a major risk factor for falls. In this review, we specify cognitive-behavioral mechanisms that produce falls and map these mechanisms onto a model of multi-system degeneration. Results from PET studies in PD fallers and findings from a recently developed animal model support the hypothesis that falls result from interactions between loss of basal forebrain cholinergic projections to the cortex and striatal dopamine loss. Striatal dopamine loss produces inefficient, low-vigor gait, posture control, and movement. Cortical cholinergic deafferentation impairs a wide range of attentional processes, including monitoring of gait, posture and complex movements. Cholinergic cell loss reveals the full impact of striatal dopamine loss on motor performance, reflecting loss of compensatory attentional supervision of movement. Dysregulation of dorsomedial striatal circuitry is an essential, albeit not exclusive, mediator of falls in this dual-system model. Because cholinergic neuromodulatory activity influences cortical circuitry primarily via stimulation of α4β2* nicotinic acetylcholine receptors, and because agonists at these receptors are known to benefit attentional processes in animals and humans, treating PD fallers with such agonists, as an adjunct to dopaminergic treatment, is predicted to reduce falls. Falls are an informative behavioral endpoint to study attentional-motor integration by striatal circuitry.
authors.affiliation: Department of Psychology, Neuroscience Program, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: msarter@umich.edu.
authors.forename: Martin
authors.initials: M
authors.lastname: Sarter
authors.affiliation: Neurology Service and Geriatric Research, Education and Clinical Center, Veterans Administration Ann Arbor Healthcare System, University of Michigan, Ann Arbor, MI 48109, USA; Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Roger L
authors.initials: RL
authors.lastname: Albin
authors.affiliation: Department of Psychology, Neuroscience Program, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Kucinski
authors.affiliation: Department of Psychology, Neuroscience Program, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Cindy
authors.initials: C
authors.lastname: Lustig
mesh_terms: D000058:Accidental Falls / Q000401:mortality; D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001288:Attention; D002540:Cerebral Cortex / Q000473:pathology*; D003342:Corpus Striatum / Q000503:physiopathology*; D004298:Dopamine / Q000378:metabolism*; D006801:Humans; D008636:Mesencephalon / Q000378:metabolism*; D010300:Parkinson Disease / Q000473:pathology / Q000503:physiopathology
chemical_list: D000109:Acetylcholine; D004298:Dopamine
keywords: Acetylcholine; Basal forebrain; Dopamine; Falls; Striatum