title: Saccade reprogramming in Friedreich ataxia reveals impairments in the cognitive control of saccadic eye movement.
abstract: Although cerebellar dysfunction has known effects on motor function in Friedreich ataxia (FRDA), it remains unclear the extent to which the reprogramming of eye movements (saccades) and inhibition of well-learned automatic responses are similarly compromised in affected individuals. Here we examined saccade reprogramming to assess the ability of people with FRDA to respond toward unexpected changes in either the amplitude or direction of an "oddball" target. Thirteen individuals with genetically confirmed FRDA and 12 age-matched controls participated in the study. The saccade reprogramming paradigm was used to examine the effect of an unpredictable "oddball" target on saccade latencies and accuracy when compared to a well-learned sequence of reciprocating movements. Horizontal eye movements were recorded using a scleral search coil eye tracking technique. The results showed a proportionally greater increase in latencies for reprogrammed saccades toward an oddball-direction target in the FRDA group when compared to controls. The FRDA group were also less accurate in primary saccade gain (i.e. ratio of saccade amplitude to target amplitude) when reprogramming saccades toward an unexpected change in direction. No significant group differences were found on any of the oddball-amplitude targets. Significant correlations were revealed between latency and disease severity as measured by the Friedreich Ataxia Rating Scale. These findings provide further support to the view that cognitive changes in FRDA may arise from disruption of cerebellar connections to cortical structures.
authors.affiliation: School of Psychological Science, La Trobe University, Bundoora, Victoria 3086, Australia. Electronic address: d.hocking@latrobe.edu.au.
authors.forename: Darren R
authors.initials: DR
authors.lastname: Hocking
authors.affiliation: Bruce Lefroy Centre for Genetic Health Research, Murdoch Childrens Research Institute, Parkville, Victoria, Australia.
authors.forename: Louise A
authors.initials: LA
authors.lastname: Corben
authors.affiliation: School of Psychology and Psychiatry, Monash University, Clayton, Victoria, Australia.
authors.forename: Joanne
authors.initials: J
authors.lastname: Fielding
authors.affiliation: Royal North Shore Hospital, St. Leonards, New South Wales, Australia.
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Cremer
authors.affiliation: Department of Neurology, Royal Melbourne Hospital, Parkville, Victoria, Australia.
authors.forename: Lynette
authors.initials: L
authors.lastname: Millist
authors.affiliation: Department of Neurology, Royal Melbourne Hospital, Parkville, Victoria, Australia.
authors.forename: Owen B
authors.initials: OB
authors.lastname: White
authors.affiliation: Bruce Lefroy Centre for Genetic Health Research, Murdoch Childrens Research Institute, Parkville, Victoria, Australia; Clinical Genetics, Department of Medicine, University of Melbourne, Austin Health, Heidelberg, Victoria, Australia.
authors.forename: Martin B
authors.initials: MB
authors.lastname: Delatycki
mesh_terms: D000328:Adult; D003071:Cognition / Q000502:physiology*; D005621:Friedreich Ataxia / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D012438:Saccades
keywords: Attention; Cerebellum; Cognition; Inherited ataxias; Saccades