title: Arrhythmokinesis is evident during unimanual not bimanual finger tapping in Parkinson's disease.
abstract: BACKGROUND
  Arrhythmokinesis, the variability in repetitive movements, is a fundamental feature of Parkinson's disease (PD). We hypothesized that unimanual repetitive alternating finger tapping (AFT) would reveal more arrhythmokinesis compared to bimanual single finger alternating hand tapping (SFT), in PD.
  
  
  METHODS
  The variability of inter-strike interval (CVISI) and of amplitude (CVAMP) during AFT and SFT were measured on an engineered, MRI-compatible keyboard in sixteen PD subjects off medication and in twenty-four age-matched controls.
  
  
  RESULTS
  The CVISI and CVAMP of the more affected (MA) and less affected (LA) sides in PD subjects were greater during AFT than SFT (P < 0.05). However, there was no difference between AFT and SFT for controls. Both CVISI and CVAMP were greater in the MA and LA hands of PD subjects versus controls during AFT (P < 0.01). The CVISI and CVAMP of the MA, but not the LA hand, were greater in PDs versus controls during SFT (P < 0.05). Also, AFT, but not SFT, detected a difference between the MA and LA hands of PDs (P < 0.01).
  
  
  CONCLUSIONS
  Unimanual, repetitive alternating finger tapping brings out more arrhythmokinesis compared to bimanual, single finger tapping in PDs but not in controls. Arrhythmokinesis during unimanual, alternating finger tapping captured a significant difference between both the MA and LA hands of PD subjects and controls, whereas that during a bimanual, single finger tapping task only distinguished between the MA hand and controls. Arrhythmokinesis underlies freezing of gait and may also underlie the freezing behavior documented in fine motor control if studied using a unimanual alternating finger tapping task.
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University, 300 Pasteur Drive, Stanford, CA 94305 USA.
authors.forename: Megan H
authors.initials: MH
authors.lastname: Trager
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University, 300 Pasteur Drive, Stanford, CA 94305 USA.
authors.forename: Anca
authors.initials: A
authors.lastname: Velisar
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University, 300 Pasteur Drive, Stanford, CA 94305 USA.
authors.forename: Mandy Miller
authors.initials: MM
authors.lastname: Koop
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University, 300 Pasteur Drive, Stanford, CA 94305 USA.
authors.forename: Lauren
authors.initials: L
authors.lastname: Shreve
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University, 300 Pasteur Drive, Stanford, CA 94305 USA.
authors.forename: Emma
authors.initials: E
authors.lastname: Quinn
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University, 300 Pasteur Drive, Stanford, CA 94305 USA ; Department of Neurosurgery, Stanford University, Stanford, CA USA.
authors.forename: Helen
authors.initials: H
authors.lastname: Bronte-Stewart
keywords: Arrhythmokinesis; Finger tapping; Parkinson’s disease; Quantitative Digitography; Rhythmicity