Objective: The aim of the study was to identify and characterize subthalamic (STN) and nigral (SNr) neurons showing gait-related activity changes. 12 Parkinson’s disease (PD) patients had been tested with a gait-like motor paradigm during neurosurgery for deep brain stimulation (DBS) of the STN.

Background: The Parkinsonian gait disorder and freezing of gait represent fairly understood, therapeutically demanding symptoms with considerable impact on quality of life. Aberrant neuronal activity within the STN and SNr, reverberating in subcortical basal ganglia-brainstem loops, might represent key elements in the pathogenesis of gait. A better understanding of the functional role of STN and SNr in gait control promote the optimization of novel therapeutic DBS approaches as the combined STN+SNr stimulation.

Method: Intraoperative microelectrode recordings during DBS surgery within the STN and SNr were performed. 12 male patients (56 ± 7 years) suffering from moderate idiopathic PD participated in the study and performed stepping movements in a supine position. Stepping at self-paced speed for 35 s was followed by short periods of stepping in response to random start and stop cues. Single- and multi-unit activity was analysed offline in relation to different aspects of the stepping movement (start and stop of the movement, heel strike of the ipsi- and contralateral limb, movement velocity).

Results: STN and SNr neurons responded to different aspects of the stepping task. In both structures, about 60 % of the units did not show any specific modulation related to the experimental paradigm. 30% of the subthalamic neurons exhibited movement-related activity modulation as an increase of the firing rate, revealing a predominant role of the STN in motor aspects of the task. The remaining 10 % of STN neurons showed a modulation in response to the start and stop signals. In contrast, respondent SNr neurons showed inconsistently modulation by motor aspects (14 %), but predominant activity changes during “cognitive” aspects of the stepping task (29 % was changing the firing rate in response to the start and stop cues).

Conclusion: This study shows for the first time specific, task-related, single unit activity changes during gait-like movements in humans. We propose differential roles of the STN and SNr cells for motor and cognitive aspects within gait control.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-differential-role-of-subthalamic-and-nigral-neurons-in-gait-control-in-parkinsons-disease-patients/