title: Control and prediction components of movement planning in stuttering versus nonstuttering adults.
abstract: OBJECTIVE
  Stuttering individuals show speech and nonspeech sensorimotor deficiencies. To perform accurate movements, the sensorimotor system needs to generate appropriate control signals and correctly predict their sensory consequences. Using a reaching task, we examined the integrity of these control and prediction components separately for movements unrelated to the speech motor system.
  
  
  METHODS
  Nine stuttering and 9 nonstuttering adults made fast reaching movements to visual targets while sliding an object under the index finger. To quantify control, we determined initial direction error and end point error. To quantify prediction, we calculated the correlation between vertical and horizontal forces applied to the object-an index of how well vertical force (preventing slip) anticipated direction-dependent variations in horizontal force (moving the object).
  
  
  RESULTS
  Directional and end point error were significantly larger for the stuttering group. Both groups performed similarly in scaling vertical force with horizontal force.
  
  
  CONCLUSIONS
  The stuttering group's reduced reaching accuracy suggests limitations in generating control signals for voluntary movements, even for nonorofacial effectors. Typical scaling of vertical force with horizontal force suggests an intact ability to predict the consequences of planned control signals. Stuttering may be associated with generalized deficiencies in planning control signals rather than predicting the consequences of those signals.
authors.forename: Ayoub
authors.initials: A
authors.lastname: Daliri
authors.forename: Roman A
authors.initials: RA
authors.lastname: Prokopenko
authors.forename: J Randall
authors.initials: JR
authors.lastname: Flanagan
authors.forename: Ludo
authors.initials: L
authors.lastname: Max
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D013342:Stuttering / Q000503:physiopathology* / Q000523:psychology; D013647:Task Performance and Analysis; D055815:Young Adult