Objective: To understand single unit recruitment strategies for upper and lower extremity movements in the human subthalamic nucleus (STN), which is the main target for deep brain stimulation (DBS) in patients with Parkinson’s disease (PD).

Background: DBS of the STN is a routine neurosurgical procedure for alleviating motor symptoms of advanced PD. Its neuronal activity has been related to tremor, hand grip force, target appearance event, and movement onset and direction, but the strategies for neuronal recruitment for kinematic control of hand movements and gait are unclear.

Methods: Subjects were 10 PD patients undergoing DBS implantation for clinical reasons (mean: 59.2 years, SD=11.7; disease duration: 11.1 years, SD=4.2; all right-handed; 8 males). Patients performed hand and feet tapping movements intra-operatively by one limb, bipedally or bimanually (in an alternating pattern), each repeated at 3 paces: patient self-selected “normal” pace, slow pace, and fast pace. During the tasks, patients wore small measurement devices that recorded kinematics (acceleration, angular velocity and orientation) in synchrony with the recording of single unit activity.

Results: We recorded the activity of 89 single units. For feet movements, both uni- and bi-pedal, normal, patient-selected, pace recruited the largest percentage of units (mean: 90%, SE: 1.2%). A significantly smaller percentage was involved in slow pace movements (mean: 86%, SE: 2.6%; p=0.042, paired-sample t-test), and an even smaller, in fast movements (mean: 79%, SE: 1.7%). For hand movements, the largest percentage of the neurons involved was during the slow pace (mean: 84%, SE: 0.6%), followed by a significantly smaller percentage during normal pace (mean: 77%, SE: 0.5%; p=0.0026, paired-sample t-test), and the smallest percentage again for the fast pace (mean: 69%, SE: 1.6%).

Conclusions: The difference in neuronal recruitment during normal and slow paces between feet and hand movements may be due to the different roles of the human upper and lower limbs in the expression of cognitive processes: for hands, expression by fine object manipulations (more neurons); for feet, reduced attention during dual tasking (less neurons). These results may, in the future, help tailor DBS to the specific hand or feet symptoms.

ISPGR 2015.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/recruitment-of-single-subthalamic-neurons-for-kinematic-control-of-hand-and-feet-movements-employs-different-strategies/