title: A perceptual discrimination task abnormally facilitates reflexive saccades in Parkinson's disease.
abstract: Numerous studies have shown that Parkinson's disease (PD) affects the ability to generate voluntary saccades and the ability to suppress reflexive saccades. The effects of PD on the generation of reflexive saccades, however, are not clear. Some studies report impairments, but there are also reports of abnormal facilitation or hyper-reflexivity of the saccade system in PD. Meanwhile, it has been reported that the concurrent performance of a perceptual discrimination task facilitates saccade initiation and reduces saccade latencies in healthy subjects [A. Montagnini & L. Chelazzi (2005)Vis. Res., 45, 3391-3401; L. Trottier & J. Pratt (2005)Vis. Res., 45, 1349-1354]. To investigate the circumstances under which the saccade system may appear hyper-reflexive in PD, we compared reflexive saccades with and without a concurrent perceptual discrimination task in 20 PD patients and 20 controls. Without the discrimination task, the PD group produced reflexive saccades at normal latencies. The discrimination task reduced saccade latencies more in the PD group than in the control group, resulting in abnormally short mean reflexive saccade latencies in the PD group. The discrimination task increased saccade gain in both groups, but saccades in the PD group remained hypometric as compared with saccades in the control group. We conclude that the attentional demands of this paradigm revealed a hypersensitivity to visual inputs in the PD group.
authors.affiliation: Van der Veer Institute for Parkinson's & Brain Research, 66 Stewart Street, Christchurch, New Zealand. saskia.vanstockum@vanderveer.org.nz
authors.forename: Saskia
authors.initials: S
authors.lastname: van Stockum
authors.forename: Michael R
authors.initials: MR
authors.lastname: Macaskill
authors.forename: Daniel
authors.initials: D
authors.lastname: Myall
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Anderson
mesh_terms: D000368:Aged; D001288:Attention / Q000502:physiology; D004192:Discrimination, Psychological / Q000502:physiology*; D053483:Eye Movement Measurements; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D010775:Photic Stimulation; D012018:Reflex / Q000502:physiology*; D012438:Saccades / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*