Neuronal population activity in the olivocerebellum encodes the frequency of essential tremor in mice and patients

The cerebellum shapes motions by encoding motor frequencies with precision and cross-individual uniformity

Understanding brain behaviour encoding or designing neuroprosthetics requires identifying precise, consistent neural algorithms across individuals. However, cerebral microstructures and activities are individually variable, posing challenges for identifying precise codes. Here, despite cerebral variability, we report that the cerebellum shapes motor kinematics by encoding dynamic motor frequencies with remarkable numerical precision and cross-individual uniformity. Using in vivo electrophysiology and optogenetics in mice, we confirm that deep cerebellar neurons encode frequencies using populational tuning of neuronal firing probabilities, creating cerebellar oscillations and motions with matched frequencies. The mechanism is consistently presented in self-generated rhythmic and non-rhythmic motions triggered by a vibrational platform or skilled tongue movements of licking in all tested mice with cross-individual uniformity. The precision and uniformity allowed us to engineer complex motor kinematics with designed frequencies. We further validate the frequency-coding function of the human cerebellum using cerebellar electroencephalography recordings and alternating current stimulation during voluntary tapping tasks. Our findings reveal a cerebellar algorithm for motor kinematics with precision and uniformity, the mathematical foundation for a brain-computer interface for motor control.

Protocol for recording physiological signals from the human cerebellum using electroencephalography

As Purkinje cells of the cerebellum have a very fast firing rate, techniques with high temporal resolution are required to capture cerebellar physiology. Here, we present a protocol to record physiological signals in humans using cerebellar electroencephalography (cEEG). We describe steps for electrode placement and recording. We then detail solutions for dealing with potential muscle, ocular, and electrical artifacts. This protocol has applications in recording patients with cerebellar disorders such as essential tremor, cerebellar ataxia, and dystonia. For complete details on the use and execution of this protocol, please refer to Pan et al.,1 Wong et al.,2 and Wang et al.3.

Reduced cerebellar rhythm by climbing fiber denervation is linked to motor rhythm deficits in mice and ataxia severity in patients

Cerebellar ataxia results from various genetic and nongenetic disorders and is characterized by involuntary movements that impair precision and motor rhythm. Here, we report that climbing fiber (CF) denervation is a common pathophysiology underlying motor rhythm loss in cerebellar ataxia. By examining cerebellar pathology in patients with spinocerebellar ataxia (SCA) types 1, 2, and 6 and multiple system atrophy, we identified CF degeneration with synaptic loss as a shared pathophysiology. Optogenetic silencing of CF synaptic activity in mice induced ataxia-like motor dysfunctions and loss of motor precision. In addition, CF silencing resulted in cerebellar and motor rhythm loss, another core feature of ataxia. This rhythm loss was predominantly CF dependent and resistant to Purkinje cell-specific lesioning by diphtheria toxin. Correspondingly, two patients with inferior olive pathology, the brain site that provides CFs to Purkinje cells, presented with ataxia and cerebellar rhythm loss. Patients with genetic or nongenetic cerebellar ataxia exhibited cerebellar rhythm loss that correlated with the Scale for the Assessment and Rating of Ataxia. Chemogenetic stimulation of CFs improved cerebellar and motor rhythms as well as motor performance in the SCA type 1 mouse model of ataxia. These results suggest that CF-dependent cerebellar rhythm loss occurs across different types of cerebellar ataxia, contributing to motor imprecision and motor rhythm loss, two defining features of ataxia.

Targeting the fundamentals for tremors: the frequency and amplitude coding in essential tremor

Essential tremor (ET) is one of the most common movement disorders with heterogeneous pathogenesis involving both genetic and environmental factors, which often results in variable therapeutic outcomes. Despite the diverse etiology, ET is defined by a core symptom of action tremor, an involuntary rhythmic movement that can be mathematically characterized by two parameters: tremor frequency and tremor amplitude. Recent advances in neural dynamics and clinical electrophysiology have provided valuable insights to explain how tremor frequency and amplitude are generated within the central nervous system. This review summarizes both animal and clinical evidence, encompassing the kinematic features of tremors, circuitry dynamics, and the neuronal coding mechanisms for the two parameters. Neural population coding within the olivocerebellum is implicated in determining tremor frequency, while the cerebellar circuitry synchrony and cerebellar-thalamo-cortical interactions play key roles in regulating tremor amplitude. Novel therapeutic strategies aimed at tuning tremor frequency and amplitude are also discussed. These neural dynamic approaches target the conserved mechanisms across ET patients with varying etiologies, offering the potential to develop universally effective therapies for ET.

Cerebellar Oscillatory Patterns in Essential Tremor: Modulatory Effects of VIM-DBS

Essential tremor (ET) is a common movement disorder, and while ventral intermediate nucleus deep brain stimulation (VIM-DBS) is a well-established treatment, its precise mechanisms or modulatory effects, particularly in relation to cerebellar oscillations, remain unclear. In this study, we hypothesized that VIM-DBS would modulate cerebellar oscillatory activity across both resting and motor task conditions, reflecting its impact on cerebello-thalamic pathways. Ten patients diagnosed with ET participated in this study. We examined the effects of VIM-DBS on mid-cerebellar oscillations during resting-state and lower-limb pedaling motor tasks. Frequency analysis was conducted on the resting-state signal and time-frequency analysis was performed on motor task-related signals. We explored the modulatory effects of VIM-DBS on oscillatory activity across delta, theta, alpha, beta, and gamma frequency bands. We found that ON VIM-DBS increased mid-cerebellar relative theta power during resting-state conditions, with no significant changes in other frequency bands. During a pedaling motor task, VIM-DBS led to significant reductions in theta, alpha, and gamma power, highlighting the frequency-specific effects of stimulation. VIM-DBS also increased peak acceleration of leg movements during the pedaling task. Furthermore, VIM-DBS selectively increased mid-frontal relative theta and beta power as well as mid-occipital relative theta power during resting condition, suggesting localized mid-cerebellar modulation. Moreover, similarity analyses between mid-cerebellar and nearby mid-occipital signals revealed differences in coherence, phase coherence, and cross-spectrum phase coherence. Overall, these results support the role of VIM-DBS in modulating mid-cerebellar oscillations in ET and provide new insights into the neural mechanisms underlying DBS efficacy.

Implantable Self-Powered Systems for Electrical Stimulation Medical Devices

With the integration of bioelectronics and materials science, implantable self-powered systems for electrical stimulation medical devices have emerged as an innovative therapeutic approach, garnering significant attention in medical research. These devices achieve self-powering through integrated energy conversion modules, such as triboelectric nanogenerators (TENGs) and piezoelectric nanogenerators (PENGs), significantly enhancing the portability and long-term efficacy of therapeutic equipment. This review delves into the design strategies and clinical applications of implantable self-powered systems, encompassing the design and optimization of energy harvesting modules, the selection and fabrication of adaptable electrode materials, innovations in systematic design strategies, and the extensive utilization of implantable self-powered systems in biological therapies, including the treatment of neurological disorders, tissue regeneration engineering, drug delivery, and tumor therapy. Through a comprehensive analysis of the latest research progress, technical challenges, and future directions in these areas, this paper aims to provide valuable insights and inspiration for further research and clinical applications of implantable self-powered systems.