Micrographia in Parkinson's disease: the effect of providing external cues.
Oliveira RM., Gurd JM., Nixon P., Marshall JC., Passingham RE.
OBJECTIVE: To investigate whether micrographia in patients with Parkinson's disease is lessened either by giving visual targets or by continually reminding them that they should write with a normal amplitude. METHODS: Eleven patients with Parkinson's disease (mean age 65.4 years) were compared with 14 control subjects (mean age 67.1 years). The subjects wrote with a stylus on a graphics tablet. There were three conditions: free writing, writing with dots to indicate the required size, and writing with continuous verbal reminders ("big"). Each condition was performed twice. RESULTS: The patients wrote with a more normal amplitude when given either the visual cues or the auditory reminders. This improvement persisted when, shortly afterwards, the patients wrote freely without external cues. The increase in amplitude was achieved mainly by an increase in movement time rather than in peak velocity. CONCLUSION: Whereas the visual cues directly specified the required amplitude the auditory reminders did not. One effect of external cues is that they draw attention to the goal, and thus encourage the patients to write less automatically.