Do Parkinson's patients feel the beat the same way we do?
We conducted a study to examine whether Parkinson's disease patients had subtle deficits in beat perception (that is, finding the regular, steady pulse that we tap our foot to when we hear a rhythm). Because a previous imaging study had found that the basal ganglia respond when a regular beat is perceived, we wanted to see if people with basal ganglia dysfunction (which occurs in Parkinson's disease), showed any deficits in beat perception.
We used rhythms created for a previous study. The metric simple rhythms are easier for most people to remember, because people feel a beat in them. The metric complex rhythms are similar, but don't give a strong feeling of a beat, so people tend to do worse in remembering these rhythms.
A Metric Simple sound
A Metric Complex sound
If Parkinson's disease patients do have a beat perception deficit, we would expect their abilities with metric simple rhythms to be not as good as healthy volunteer
We used rhythms created for a previous study. The metric simple rhythms are easier for most people to remember, because people feel a beat in them. The metric complex rhythms are similar, but don't give a strong feeling of a beat, so people tend to do worse in remembering these rhythms.
A Metric Simple sound
A Metric Complex sound
If Parkinson's disease patients do have a beat perception deficit, we would expect their abilities with metric simple rhythms to be not as good as healthy volunteer
The Task
Parkinson's disease patients and healthy volunteers listened to 3 presentations of a rhythm. Their task was to decide if the third presentation was the same as or different from the first 2 presentations.
A task example with 3 presentations: is the 3rd the same as or different from the first 2? (metric simple rhythms).
A task example with 3 presentations: is the 3rd the same as or different from the first 2? (metric complex rhythms).
Download an Eprime version of the task.
A task example with 3 presentations: is the 3rd the same as or different from the first 2? (metric simple rhythms).
A task example with 3 presentations: is the 3rd the same as or different from the first 2? (metric complex rhythms).
Download an Eprime version of the task.
The Results
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Parkinson's patients showed a significant problem in detecting changes in the metric simple condition (compared to healthy volunteers). This is shown on the left hand side of the graph below (the asterisks indicate that Parkinson's patients do reliably worse than healthy volunteers with metric simple rhythms).
However, for the metric complex rhythms, their performance was similar to healthy volunteers (right side of graph: there performance was a little bit lower, but this was not statistically significant, so the Parkinson's patients were not reliably worse for the metric complex rhythms). This suggests that Parkinson's disease patients have difficulty in either perceiving the beat, or using it to help their performance during the task. |