Session Time: 12:00pm-1:30pm
Objective: To test the effects of GPi DBS on susceptibility to impulsive action errors and the proficiency of reactive inhibitory control to counteract interference from action impulses.
Background: Basal ganglia are key nodes in circuitry that select and inhibit competing action commands in the motor system. Previously, we showed that STN DBS improves inhibitory control over undesired action impulses.
Methods: PD patients (n=13) with unilateral GPi DBS performed a Simon conflict task during “on” and “off” DBS stimulation and in the “off” medication state. The Simon task produces conflict between an impulsive action tendency and a goal-directed action, which interferes with response time and accuracy for executing the goal action. We applied the Dual Process Activation-Suppression (DPAS) model to separate the initial bottom-up strength of action impulses (i.e., percentage of fast, impulsive errors) from the proficiency of top-down reactive inhibition to counteract unwanted motor impulses (i.e., slope reduction of interference).
Results: The Simon task produced strong interference from impulsive action tendencies (F(1,11)=23.69, p<.001). Compared to the DBS “off” state, stimulating GPi, irrespective of which implanted side, led to increases in response time interference from impulsive action tendencies, (F(1,11)=11.22, p=.006) without affecting mean reaction speed, (F(1,11)=0.82, p=.38). Critically, GPi DBS, irrespective of side, produced higher impulsive error rates, (F(1,11)=5.16, p<.05), but had no effect on the proficiency of reactive inhibitory control, (F(1,11)=0.66, p=.43).
|Male, n (%)||8 (61.5)|
|Age, mean (SD)||62.6 (6.8)|
|Years since symptom onset, mean (SD)||12.8 (6.1)|
|Years since diagnosis, mean (SD)||9.9 (3.5)|
|Initial motor symptom|
|Side of initial motor symptom R/L||6/6|
|LED, mean (SD)||1263.5 (336.3)|
|Years since DBS surgery, mean (SD)||2.5 (1.9)|
|DBS side R/L||5/8|
|UPDRS III, mean (SD)|
|"Off" med "Off" stim||39.8 (10.7)|
|"Off" med "On" stim||29.2 (6.4)|
|Hoehn & Yahr, median||2.5|
|QUIP-RS. mean (SD)||10.7 (20.8)|
Conclusions: Stimulating GPi reduces the initial gating of bottom-up impulsive action tendencies, leading to enhanced motor system conflict and greater susceptibility to acting on strong impulsive actions. However, unlike STN DBS, GPi DBS does not alter top-down, reactive inhibitory control engaged to counteract the activation of incorrect action impulses in the motor system.
To cite this abstract in AMA style:D. Martinez-Ramirez, C.S. Little, J.P. Chapman, S. Carbunaru, J.C. Giugni, M.W. Vasquez, F. Chai, R. Walz, A. Sririam, K. Kanoff, S.A. Wylie, M.S. Okun. Impulsive action tendencies in GPi DBS Parkinson’s patients [abstract]. Mov Disord. 2016; 31 (suppl 2). https://www.mdsabstracts.org/abstract/impulsive-action-tendencies-in-gpi-dbs-parkinsons-patients/. Accessed September 27, 2023.
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MDS Abstracts - https://www.mdsabstracts.org/abstract/impulsive-action-tendencies-in-gpi-dbs-parkinsons-patients/