title: Speech motor programming in apraxia of speech: evidence from a delayed picture-word interference task.
abstract: OBJECTIVE
  Apraxia of speech (AOS) is considered a speech motor programming impairment, but the specific nature of the impairment remains a matter of debate. This study investigated 2 hypotheses about the underlying impairment in AOS framed within the Directions Into Velocities of Articulators (DIVA; Guenther, Ghosh, & Tourville, 2006) model: The retrieval hypothesis states that access to the motor programs is impaired, and the damaged programs hypothesis states that the motor programs themselves are damaged.
  
  
  METHODS
  The experiment used a delayed picture-word interference paradigm in which participants prepare their response and auditory distracters are presented with the go signal. The overlap between target and distracter words was manipulated (i.e., shared sounds or no shared sounds), and participants' reaction times (RTs) were measured. Participants included 5 speakers with AOS (4 with concomitant aphasia), 2 speakers with aphasia without AOS, and 9 age-matched control speakers.
  
  
  RESULTS
  The control speakers showed no effects of distracter type or presence. The speakers with AOS had longer RTs in the distracter condition compared to the no-distracter condition. The speakers with aphasia without AOS were comparable to the control group in their overall RTs and RT pattern.
  
  
  CONCLUSIONS
  Results provide preliminary support for the retrieval hypothesis, suggesting that access to motor programs may be impaired in speakers with AOS. However, the possibility that the motor programs may also be damaged cannot be ruled out.
authors.affiliation: University of Arizona, Tucson, AZ, USA. mailend@email.arizona.edu
authors.forename: Marja-Liisa
authors.initials: ML
authors.lastname: Mailend
authors.forename: Edwin
authors.initials: E
authors.lastname: Maas
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000368:Aged; D001037:Aphasia / Q000503:physiopathology* / Q000628:therapy; D001072:Apraxias / Q000503:physiopathology* / Q000628:therapy; D001288:Attention / Q000502:physiology; D055317:Evidence-Based Practice; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010470:Perceptual Masking / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D011930:Reaction Time / Q000502:physiology; D013060:Speech / Q000502:physiology*; D013064:Speech Disorders / Q000503:physiopathology* / Q000628:therapy; D013068:Speech Production Measurement; D013070:Speech Therapy
keywords: aphasia; apraxia of speech; speech motor control; speech production