Ten patients with mild to moderate Parkinson’s disease were compared with
ten age-matched normal controls in a series of saccadic paradigms in order
to test various hypotheses relating to the origin of the Parkinsonian saccadic
defect. The paradigms comprised a reflex saccade paradigm, a standard
remembered saccade paradigm, a remembered saccade paradigm with delayed
centre-offset, and a remembered saccade paradigm with a second target flash
immediately prior to saccade execution. Finally, subjects executed both reflex
and remembered saccades in a standard remembered paradigm (the “twosaccade”
paradigm). As has been reported previously, Parkinsonian subjects
demonstrated hypometria on all remembered saccade paradigms, particularly
the “two-saccade” paradigm. There was, however, no significant difference
between the first three remembered saccade paradigms. These studies serve
to refute a simple attentional capture hypothesis, and a hypothesis that
suggests that the abnormality of remembered saccades is due to concurrent reflex saccade suppression. On the basis of the results, further hypotheses
are advanced in an attempt to explain all published work on Parkinsonian
saccades.