[Truncated abstract] There is overwhelming evidence that PD leads to impairments in executing voluntary movements. However, it is less clear whether it also leads to impairment in the preparation of movement. The current investigation first aims to further our understanding of motor preparation in people with PD. Two techniques are commonly used to assess motor preparation. These are the manipulation of response complexity and cueing response-related information in advance of the imperative signal. They were both incorporated into a motor task in which participants performed two-movement sequences on a response board. In Experiment 1, people with PD (comprising two groups one on their anti-Parkinsonian medication, and the other following a delay in its normal administration) showed patterns in their motor performance that was similar to healthy age-matched adults. They showed lengthening in their reaction time (RT) with increased response complexity, indicating that the sequences were prepared before their initiation. In addition, both of the PD groups, as well as the healthy adult group, showed shorter RTs with valid cueing and longer RTs with invalid cueing relative to the neutral cue condition. In response to a part-invalid cue (with both valid and invalid information) all three groups had very similar RTs to that in the neutral cue condition. ... in the third experiment, participants were first presented with a sequence to perform, and then, while initiating and executing that sequence, they were presented with a second sequence, providing either valid or invalid visual information about the twomovement sequence. It was expected that if invalid visual information evokes a stronger obligatory response in people with PD, then these participants would experience greater difficulties ignoring such information. This was not found to be the case. Rather the PD group showed a similar pattern of performance to the healthy adults. This indicates that they were able to ignore visual information when it was invalid and unhelpful, and so suggests that people with PD use external information strategically. The results presented in this thesis suggest that motor preparation is largely intact in people with PD. Motor preparation may, however, be incomplete under reduced visual information. Furthermore, while visual information may be particularly important to people with PD, it does not seem to evoke a stronger obligatory response than in healthy adults. Rather, people with PD seem to use external information strategically.
|Publication status||Unpublished - 2006|