title: Voice acoustic changes during bilateral subthalamic stimulation in patients with Parkinson's disease.
abstract: OBJECTIVE
  The purpose of this study was to investigate the effects of bilateral subthalamic nucleus deep brain stimulation on the phonation of patients with Parkinson's disease in three drug-free conditions: (1) stimulation off, (2) with clinically optimised stimulation parameters, and (3) subthreshold overstimulation, in order to detect differences following voice analysis.
  
  
  METHODS
  Conversational speech and sustained vowel sounds /a/, /i/, /o/, /u/ and high /i/ were recorded from 22 PD patients. Perceptual analysis, perturbation jitter, shimmer, noise-to-harmonics ratio, and nonlinear dynamic analysis (NDA) with detrended fluctuation analysis and recurrence period density entropy were measured and compared to the above conditions. Quadratic discriminant analysis (QDA) was used to investigate stimulation conditions for given acoustic data.
  
  
  RESULTS
  The changes of perturbation measurements for the above conditions were not significant. With differences between vowels, NDA showed more significant changes and more powerful correlation with perceptual scores than perturbation measurements. NDA was significantly more sensitive during the QDA of the conditions.
  
  
  CONCLUSIONS
  Acoustic voice analysis of sustained vowels can help with recognizing the overstimulated condition, and, with an appropriate test battery and software package including nonlinear dynamic analysis, it can be a valuable tool for fine adjustments of stimulation parameters.
authors.affiliation: Department of Neurosurgery, St. John's Hospital Budapest, 1-3 Diós árok, H-1125 Budapest, Hungary. valalik@parkinson.hu
authors.forename: István
authors.initials: I
authors.lastname: Valálik
authors.forename: György
authors.initials: G
authors.lastname: Smehák
authors.forename: László
authors.initials: L
authors.lastname: Bognár
authors.forename: András
authors.initials: A
authors.lastname: Csókay
mesh_terms: D000368:Aged; D001307:Auditory Perception; D046690:Deep Brain Stimulation; D016002:Discriminant Analysis; D004566:Electrodes; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D010300:Parkinson Disease / Q000503:physiopathology / Q000628:therapy*; D012727:Sex Characteristics; D013060:Speech; D013067:Speech Perception; D020531:Subthalamic Nucleus; D014057:Tomography, X-Ray Computed; D014831:Voice