Characterising Upper Limb Movements in Huntington's Disease and the Impact of Restricted Visual Cues.

Jessica Despard,Nellie Georgiou-Karistianis,Govinda Poudel,Bleydy Dimech-Betancourt,Andrew Churchyard,Anne-Marie Ternes

doi:10.1371/journal.pone.0133709

Jessica Despard, Nellie Georgiou-Karistianis + Show 4 more

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https://doi.org/10.1371/journal.pone.0133709

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Abstract

BackgroundVoluntary motor deficits are a common feature in Huntington's disease (HD), characterised by movement slowing and performance inaccuracies. This deficit may be exacerbated when visual cues are restricted.ObjectiveTo characterize the upper limb motor profile in HD with various levels of difficulty, with and without visual targets.MethodsNine premanifest HD (pre-HD), nine early symptomatic HD (symp-HD) and nine matched controls completed a motor task incorporating Fitts' law, a model of human movement enabling the quantification of movement timing, via the manipulation of task difficulty (i.e., target size, and distance between targets). The task required participants to make reciprocal movements under cued and blind conditions. Dwell times (time stationary between movements), speed, accuracy and variability of movements were compared between groups.ResultsSymp-HD showed significantly prolonged and less consistent movement times, compared with controls and pre-HD. Furthermore, movement planning and online control were significantly impaired in symp-HD, compared with controls and pre-HD, evidenced by prolonged dwell times and deceleration times. Speed and accuracy were comparable across groups, suggesting that group differences observed in movement time, variability, dwell time and deceleration time were evident over and above simple performance measures. The presence of cues resulted in greater movement time variability in symp-HD, compared with pre-HD and controls, suggesting that the deficit in movement consistency manifested only in response to targeted movements.ConclusionsCollectively, these findings provide evidence of a deficiency in both motor planning, particularly in relation to movement timing and online control, which became exacerbated as a function of task difficulty during symp-HD stages. These variables may provide a more sensitive measure of motor dysfunction than speed and/or accuracy alone in symp-HD.

Highlights

Huntington’s disease (HD) is an autosomal-dominant neurodegenerative disorder caused by the pathological expansion of a CAG trinucleotide repeat, disrupting cognitive, affective and motor functions [1,2,3]
Movement planning and online control were significantly impaired in symptomatic HD (symp-HD), compared with controls and premanifest stage of HD (pre-HD), evidenced by prolonged dwell times and deceleration times
Speed and accuracy were comparable across groups, suggesting that group differences observed in movement time, variability, dwell time and deceleration time were evident over and above simple performance measures

Summary

Introduction

Huntington’s disease (HD) is an autosomal-dominant neurodegenerative disorder caused by the pathological expansion of a CAG trinucleotide repeat, disrupting cognitive, affective and motor functions [1,2,3]. While the focus of recent research has predominantly entailed the use of advanced neuroimaging technologies to track neuronal activity [7,8,9], their functional relevance has been less well understood [4] It is the behavioural impact at a functional level that renders an individual incapable of living independently many studies have characterised motor deficits in HD [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29], most notably focus on rudimentary measures, such as speed and accuracy, and often comprise of simple finger tapping tasks [11,30]. This deficit may be exacerbated when visual cues are restricted

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