Cross, K. A. | bioRxiv Science

bioRxiv2023

Dopamine lesions alter the striatal encoding of single-limb gait

The striatum an important role in motor control, and neurons in this area encode the bodys initiation, cessation, and speed of locomotion. However, it remains unclear whether the same neurons also encode the step-by-step rhythmic motor patterns of individual limbs that characterize gait. By combining high-speed video tracking, electrophysiology, and optogenetic tagging, we found that a sizable population of both D1 and D2 receptor expressing medium spiny projection neurons (MSNs) were phase-locked to the gait cycle of individual limbs in mice. Healthy animals showed balanced limb phase-locking between D1 and D2 MSNs, while dopamine depletion led to stronger phase-locking in D2 MSNs. These findings indicate that striatal neurons represent gait on a single-limb and step basis, and suggest that elevated limb phase-locking of D2 MSNs may underlie some of the gait impairments associated with dopamine loss.

neuroscience↗

bioRxiv2020

Movement-related changes in pallidocortical synchrony differentiate action execution and observation in humans

Suppression of local and network alpha (8-12 Hz) and beta (12-35 Hz) oscillations in the human basal ganglia-thalamocortical (BGTC) circuit is a prominent feature of movement. Local alpha/beta power, cross-region beta phase coupling, and phase-amplitude coupling (PAC) have all been shown to be suppressed during movement in multiple nodes of the BGTC. However, the specificity of these various movement-related changes to actual movement execution remains poorly understood. To differentiate signals that are specifically related to movement execution, we compared changes in globus pallidus internus (GPi) and motor cortical local oscillatory activity and coupling (cross-region phase coupling and local PAC) during movement execution and movement observation in 12 patients with Parkinson disease undergoing deep brain stimulator implantation. We hypothesized that network coupling is more directly related to movement execution than local power changes, given the putative role of pathological network coupling in movement disorders such as Parkinson disease. We observed suppression of alpha/beta power during action observation and execution in the globus pallidus and motor cortex during both action execution and action observation. In contrast, pallidocortical coherence and GPi and motor cortical alpha/beta-gamma PAC were significantly suppressed only during action execution. Our results demonstrate a functional dissociation within the BG-cortical network during action execution and observation in which suppression of BG-cortical functional connectivity and local phase amplitude coupling are features specifically of overt movement, suggesting a particularly important role in motor execution. This has implications for identification and use of intracranial signals for closed loop brain stimulation therapies.

neuroscience↗