This research study examined motor control and procedural learning abilities in the oral and manual motor systems of adults who stutter, using people with Parkinson's disease, and age-matched controls as comparison groups. Participants in this study were asked to track a moving target on a computer screen with their jaw and with their dominant hand. Specifically, we compared their tracking accuracy for predictable and unpredictable signals. Procedural learning (defined as increased accuracy over time) was assessed by examining changes in tracking accuracy within a single tracking trial and between consecutive tracking trials of the same predictable condition.
There were two main findings in this study related to tracking accuracy and procedural learning in people who stutter (PWS) and age-matched controls (CPWS). First, our analyses revealed that there was no significant difference between PWS and CPWS in the accuracy of tracking of either predictable or unpredictable conditions for either the hand or the jaw, although a trend was observed in which PWS performed more poorly in both for decreased accuracy. Second, both PWS and CPWS showed evidence of procedural learning to the same extent.
There were two main findings in this study related to tracking accuracy and procedural learning in people who have Parkinson's disease (PPD) and age-matched controls (CPPD). First, tracking accuracy analyses revealed that PPD performed significantly more poorly than CPPD during jaw tracking of predictable conditions, but they were not significantly different from CPPD in jaw tracking of unpredictable conditions. During hand tracking PPD differed significantly from CPPD in tracking of both predictable and unpredictable conditions for their less accurate performance. Second, there was no significant difference between the two groups in the extent of procedural learning during jaw tracking. However, during hand tracking the PPD group improved less with time than the CPPD, suggesting that the PPD group had reduced procedural learning ability in the manual motor domain.
Lastly, age was found to be an important factor determining tracking accuracy in our participants. Younger participants (PWS and CPWS) in the age range of 18-40 years had significantly better accuracy of jaw and hand tracking than the older individuals (PPD and CPPD) in the age range of 57-79 years.