title: The dynamics of resting and postural tremor in Parkinson's disease.
abstract: OBJECTIVE
  The study examines the time and frequency structure of Parkinson's disease tremor in patients that exhibit no clinical signs of tremor.
  
  
  METHODS
  Eight mild to moderate Parkinson's disease and 8 matched control subjects maintained their limb in a constant position (30 s) under a postural finger, postural hand and resting tremor condition. Finger acceleration from the middle phalange, electromyographic (EMG) activity from extensor digitorum communis and flexor digitorum superficialis (FDS) were recorded.
  
  
  RESULTS
  The data confirmed that there were no differences in the amount of limb motion and the modal frequency was around 9 Hz for each subject group. The time-dependent organization of tremor was more regular (lower approximate entropy [ApEn]) in Parkinson's disease. Both time and frequency analyses between the acceleration and extensor EMG signals demonstrate a reduction in the 20-25 Hz tremor component and an increase in the 8-12 Hz region of tremor.
  
  
  CONCLUSIONS
  The results are discussed in relation to the proposal that increased regularity results from an increase in motor unit synchronization at 8-12 Hz and a reduction in the amplitude of the 20-25 Hz tremor component. The time and frequency structure of tremor may be useful in assessing individuals with Parkinson's disease.
authors.affiliation: Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802, USA. dev107@psu.edu
authors.forename: D E
authors.initials: DE
authors.lastname: Vaillancourt
authors.forename: K M
authors.initials: KM
authors.lastname: Newell
mesh_terms: D000368:Aged; D004576:Electromyography; D005260:Female; D005385:Fingers / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000503:physiopathology*; D010300:Parkinson Disease / Q000503:physiopathology*; D011187:Posture