title: Motion perception deficit in Down Syndrome.
abstract: It is a well established fact that Down Syndrome (DS) individuals have a tendency to develop Alzheimer's disease (AD) (Lott, I.T., Head, E., 2005. Alzheimer disease and Down syndrome: factors in pathogenesis. Neurobiol. Aging 26, 383-389). They have therefore been proposed as a model to study the pre-dementia stage of Alzheimer's (Mann, D.M., 1988. The pathological association between Down syndrome and Alzheimer disease. Mech. Ageing Dev. 43, 99-136). One of the specific deficits exhibited by AD patients is optic flow motion perception (Tetewsky, S.J., Duffy, C.J., 1999. Visual loss and getting lost in Alzheimer's disease. Neurology 52, 958-965), but there are no corresponding systematic studies in DS individuals. We performed sensitivity measurements to optic flow with Visual Evoked Potentials (VEP) and psychophysical techniques in a group of young DS participants with mild mental retardation and without significant Alzheimer's clinical symptoms. We found a significant reduction in direction discrimination sensitivity to optic flow (random dots moving in radial, rotational and translational trajectories) in DS participants compared to mental age-matched controls, while their sensitivity to direction of control moving stimuli (sinusoidal gratings) was similar to age-matched controls. Measurements of Visual Evoked Potentials (VEP) showed no response to optic flow, although the response to control stimuli (contrast-reversal checkerboard patterns) was significant. Overall, our results show a selective and substantial deficit in the perception of optic flow motion and a corresponding suppression of electroencephalographic activity in DS individuals, thus establishing a further common trait between Down Syndrome and Alzheimer's disease.
authors.affiliation: NEUROFARBA Department of Neurosciences, Psychology, Drug Research and Child Health, Section of Psychology, University of Florence, Florence, Italy. Electronic address: maria.delviva@unifi.it.
authors.forename: Maria Michela
authors.initials: MM
authors.lastname: Del Viva
authors.affiliation: NEUROFARBA Department of Neurosciences, Psychology, Drug Research and Child Health, Section of Psychology, University of Florence, Florence, Italy.
authors.forename: Arianna
authors.initials: A
authors.lastname: Tozzi
authors.affiliation: Department of Developmental Neuroscience, Stella Maris Scientific Institute, Pisa, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Bargagna
authors.affiliation: Department of Developmental Neuroscience, Stella Maris Scientific Institute, Pisa, Italy; Division of Child Neurology and Psychiatry, Department of Procreation and Developmental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cioni
mesh_terms: D000328:Adult; D004314:Down Syndrome / Q000150:complications / Q000503:physiopathology*; D005074:Evoked Potentials, Visual; D006801:Humans; D009039:Motion Perception / Q000502:physiology*; D057849:Optic Flow; D010468:Perceptual Disorders / Q000209:etiology / Q000503:physiopathology*; D011601:Psychophysics; D055815:Young Adult
keywords: Alzheimer's disease; Down Syndrome; Motion perception; Optic flow