Reverse Visually Guided Reaching in Patients with Parkinson's Disease.

Area of Science:

• Neuroscience
• Cognitive Science
• Neurology

Background:

• Parkinson's disease (PD) is characterized by motor symptoms and non-motor executive cognitive dysfunction, including deficits in inhibitory control.
• Subthalamic nucleus deep brain stimulation (STN-DBS) and dopamine replacement therapy (DRT) improve motor function in PD but their impact on inhibitory control is not fully understood.
• STN-DBS may exacerbate inhibitory control deficits, particularly in tasks requiring the suppression of prepotent responses or complex cognitive loads.

Purpose of the Study:

• To evaluate the effect of anti-Parkinson's therapies (DRT and STN-DBS) on inhibitory control using a novel task.
• To assess the utility of the reverse visually guided reaching (RVGR) task in simultaneously measuring motor performance and response inhibition in PD patients.
• To determine if RVGR can aid in preoperative screening for inhibitory control deficits and in titrating STN-DBS therapy.

Main Methods:

• Recruited 55 healthy controls, 26 PD patients on DRT, and 7 PD patients on STN-DBS and DRT.
• Administered a reverse visually guided reaching (RVGR) task, a hand-based antisaccade paradigm, and a visually guided reaching (VGR) task.
• Assessed reaction time, mean speed, and direction errors to quantify motor performance and inhibitory control.

Main Results:

• All groups showed longer reaction times and slower mean speeds in RVGR compared to VGR, with deficits being more pronounced in untreated PD patients.
• DRT, STN-DBS, or combined therapy improved reaction time and speed in RVGR more than in VGR.
• STN-DBS (with or without DRT) led to an increase in direction errors, correlated with decreased reaction time, indicating reduced proactive inhibitory control.

Conclusions:

• The RVGR task effectively quantifies the benefits of STN-DBS on bradykinesia and the associated reduction in proactive inhibitory control.
• STN-DBS treatment in PD patients can improve motor symptoms while concurrently diminishing inhibitory control.
• The RVGR task shows potential for preoperative screening of inhibitory control deficits and for optimizing STN-DBS titration to balance motor improvement and cognitive function.