title: Abnormal Electrophysiological Motor Responses in Huntington's Disease: Evidence of Premanifest Compensation.
abstract: BACKGROUND
  Huntington's disease (HD) causes progressive motor dysfunction through characteristic atrophy. Changes to neural structure begin in premanifest stages yet individuals are able to maintain a high degree of function, suggesting involvement of supportive processing during motor performance. Electroencephalography (EEG) enables the investigation of subtle impairments at the neuronal level, and possible compensatory strategies, by examining differential activation patterns. We aimed to use EEG to investigate neural motor processing (via the Readiness Potential; RP), premotor processing and sensorimotor integration (Contingent Negative Variation; CNV) during simple motor performance in HD.
  
  
  METHODS
  We assessed neural activity associated with motor preparation and processing in 20 premanifest (pre-HD), 14 symptomatic HD (symp-HD), and 17 healthy controls. Participants performed sequential tapping within two experimental paradigms (simple tapping; Go/No-Go). RP and CNV potentials were calculated separately for each group.
  
  
  RESULTS
  Motor components and behavioural measures did not distinguish pre-HD from controls. Compared to controls and pre-HD, symp-HD demonstrated significantly reduced relative amplitude and latency of the RP, whereas controls and pre-HD did not differ. However, early CNV was found to significantly differ between control and pre-HD groups, due to enhanced early CNV in pre-HD.
  
  
  CONCLUSIONS
  For the first time, we provide evidence of atypical activation during preparatory processing in pre-HD. The increased activation during this early stage of the disease may reflect ancillary processing in the form of recruitment of additional neural resources for adequate motor preparation, despite atrophic disruption to structure and circuitry. We propose an early adaptive compensation mechanism in pre-HD during motor preparation.
authors.affiliation: Research School of Psychology, College of Medicine, Biology, & Environment, Australian National University, Canberra, Australia.
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Turner
authors.affiliation: School of Psychology & Illawarra Health & Medical Research Institute, University of Wollongong, Wollongong, Australia.
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Croft
authors.affiliation: School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University, Victoria, Australia; Calvary Health Care Bethlehem Hospital, Caulfield, Victoria, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Churchyard
authors.affiliation: Research Centre for the Neurosciences of Ageing, Academic Unit of Psychiatry and Addiction Medicine, Australian National University Medical School, Canberra Hospital, Canberra, Australia; Melbourne Neuropsychiatry Centre, Department of Psychiatry, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Australia.
authors.forename: Jeffrey C L
authors.initials: JC
authors.lastname: Looi
authors.affiliation: Research School of Psychology, College of Medicine, Biology, & Environment, Australian National University, Canberra, Australia; School of Psychology & Illawarra Health & Medical Research Institute, University of Wollongong, Wollongong, Australia.
authors.forename: Deborah
authors.initials: D
authors.lastname: Apthorp
authors.affiliation: School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University, Victoria, Australia.
authors.forename: Nellie
authors.initials: N
authors.lastname: Georgiou-Karistianis
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology; D003265:Contingent Negative Variation; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006801:Humans; D006816:Huntington Disease / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D009483:Neuropsychological Tests; D011930:Reaction Time / Q000502:physiology*