Behavioral Inhibition Errors in Parkinson's Disease Tested Using an Antisaccade and Antitapping Task

Background: The antisaccade (AS) paradigm is frequently used to assess errors in reflexive behavioral responses in Parkinson's disease (PD) patients. Although PD pathology of frontal-striatal circuits suggests increased errors, reports on sensitivity and specificity of the AS task are lacking. We increased the level of cognitive complexity by adding to the AS task an antitapping instruction, i.e. an antisaccade and antitapping (ASAT) task. Objective: In this study, we compared saccadic error rates between PD patients and age-matched controls in 1) an AS task, using only eye movements and 2) an ASAT task, using eye and hand movements. Methods: 30 PD patients en 30 healthy age-matched controls performed an AS task and an ASAT task. The measurement setup consisted of a touch screen, an eye tracking system and a motion capture system. Error rates and eye - and hand latencies were compared between groups. Results: PD patients show higher error rates in the ASAT task, but not in the AS task compared to controls. In correctly performed ASAT task trials, PD patients are on average 60 milliseconds faster to initiate an eye movement. Subject classification based on error rates and eye latencies in the ASAT task results in a sensitivity of 0.77 and a specificity of 0.63. Conclusions: The results suggest that saccadic error rates and eye latencies in the cognitively more demanding ASAT task are sensitive measures to differentiate PD patients from controls. This task is a potentially useful addition to current methods to investigate visuomotor deficits in PD.