Analysis of volition latency on antisaccadic eye movements

The antisaccadic paradigm can be applied to test the suppression of reflexi ve saccades and the activation of volitional saccades simultaneously. The i mpaired frontal cortex has been shown to have difficulty in suppressing ref lexive saccade (prosaccade) to make a successful antisaccade. Degraded anti saccade performance can also be observed in patients with Parkinson's disea se (PD). The studies of PD based on the prosaccadic and antisaccadic paradi gms have shown controversial findings; the latency between patients and age -matched controls could be either with or without significant difference. E ven with this inconsistency, our previous study and recent analysis have su pported that the latency of both prosaccade and antisaccade increases signi ficantly for patients with PD. The objective of this study is to investigat e whether prolonged antisaccade latency is caused by the affected volitiona l decision process (volition latency) or simply by the delayed initiation o f saccade with direction opposite to the cue, by measuring prosaccade and a ntisaccade latency from the intermingled paradigms. Eleven mildly affected patients with idiopathic PD and eight age-matched normal subjects were test ed in this study. As compared to the age-matched control, the results showe d that prosaccade, antisaccadic, and volition latency of the patients was s ignificantly elevated (P<0.01). We conclude that antisaccade performance fo r the PD patients was degraded for both the volition decision process and t he initiation of saccade with direction opposite to the cue. Also, volition latency analysis is a more objective method than prosaccade and antisaccad e latency analysis, which can be compared among results obtained from diffe rent analysis methodologies. (C) 1999 IPEM. Published by Elsevier Science L td. All rights reserved.