title: Specific impairment of visual spatial covert attention mechanisms in Parkinson's disease.
abstract: Visual deficits in early and high level processing nodes have been documented in Parkinson's disease (PD). Non-motor high level visual integration deficits in PD seem to have a cortical basis independently of a low level retinal contribution. It is however an open question whether sensory and visual attention deficits can be separated in PD. Here, we have explicitly separated visual and attentional disease related patterns of performance, by using bias free staircase procedures measuring psychophysical contrast sensitivity across visual space under covert attention conditions with distinct types of cues (valid, neutral and invalid). This further enabled the analysis of patterns of dorsal-ventral (up-down) and physiological inter-hemispheric asymmetries. We have found that under these carefully controlled covert attention conditions PD subjects show impaired psychophysical performance enhancement by valid attentional cues. Interestingly, PD patients also show paradoxically increased visual homogeneity of spatial performance profiles, suggesting flattening of high level modulation of spatial attention. Finally we have found impaired higher level attentional modulation of contrast sensitivity in the visual periphery, where mechanisms of covert attention are at higher demands. These findings demonstrate a specific loss of attentional mechanisms in PD and a pathological redistribution of spatial mechanisms of covert attention.
authors.affiliation: Visual Neuroscience Laboratory, IBILI, Faculty of Medicine, University of Coimbra, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Sampaio
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Bobrowicz-Campos
authors.forename: Rui
authors.initials: R
authors.lastname: André
authors.forename: Inês
authors.initials: I
authors.lastname: Almeida
authors.forename: Pedro
authors.initials: P
authors.lastname: Faria
authors.forename: Cristina
authors.initials: C
authors.lastname: Januário
authors.forename: António
authors.initials: A
authors.lastname: Freire
authors.forename: Miguel
authors.initials: M
authors.lastname: Castelo-Branco
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000209:etiology*; D003463:Cues; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications*; D010468:Perceptual Disorders / Q000175:diagnosis / Q000209:etiology*; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology; D012720:Severity of Illness Index; D013028:Space Perception / Q000502:physiology*; D013223:Statistics as Topic; D014796:Visual Perception / Q000502:physiology*