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Predictive responses in Parkinson's disease: manual keypresses and saccadic eye movements to regular stimulus events

Research output: Contribution to journalJournal article

Published

Journal publication date1989
JournalJournal of Neurology Neurosurgery and Psychiatry
Journal number9
Volume52
Number of pages10
Pages1033-1042
Original languageEnglish

Abstract

In a coincidence timing task, Parkinsonian patients and a control group were instructed
to synchronise a keypress with the onset of a visual signal which had been preceded by a regular train
of warning signals. Although the Parkinsonian group had previously exhibited slower reactions in a
conventional simple reaction-time task, they were able to generate predictive responses that fell as
close to the target onset as the controls' but showed greater variability. In a second experiment,
Parkinsonian patients and controls made saccadic eye movements to a visual target that stepped at
regular intervals between two fixed locations. After a few trials all the subjects tended to make predictive saccades that were initiated before the target excursion. However, the Parkinsonian group were slower to develop this strategy and when they did their saccades became considerably more
hypometric than those of the controls. Both groups were able to maintain predictive responding even
when the visual target disappeared and responses were paced by a buzzer. We concluded that
Parkinsonian patients are capable ofinitiating predictive responses of the eye and the hand, at least in
some circumstances, but such responses tend to be inaccurate in execution. This, in turn, may dispose
the Parkinsonian patient against predictive movement.