a) Mean reaction times (RT) to go arrows as a function of Group (DAAg Monotherapy, DAAg with Levodopa cotherapy) and Medication State (on DAA, off DAA). Patients taking DAAg monotherapy showed a significant speeding of RT On compared to Off DAA medications. Patients taking both DAAg and Levodopa showed a reduction in RT when compared to task performance on Levodopa only. Error bars reflect the standard error of the mean. b) Stop signal reaction time (SSRT) as a function of Group (DAAg Monotherapy, DAAg with Levodopa cotherapy) and Medication State (on DAA, off DAA). Mean SSRT was marginally, but non-significantly, faster among patients on Levodopa cotherapy compared to those on DAAg Monotherapy, regardless of medication state. Error bars reflect standard error of the mean.