Biology subjects

Tai, Y. F.

Publications and source records attributed to Tai, Y. F..

3 recordsLinked to original sources

bioRxiv2025

Propagation of Beta bursts from the motor cortex to the motor units of multiple upper-limb muscles

Beta band (13-30 Hz) oscillations are crucial for motor control, though their functional significance remains debated. Recent research suggests that beta activity occurs in transient bursts, which may better capture its role in movement regulation than sustained oscillations. While cortical and sub- cortical beta bursts have been extensively studied, their transmission to muscles--particularly in the upper limb--remains poorly understood and has been limited by traditional bipolar EMG techniques. In this study, we used high-density surface electromyography (HDsEMG) and electroencephalography (EEG) to investigate the cortico-peripheral dynamics of beta bursts in forearm extensor muscles during isometric contractions at the motor unit (MU) level. We show that MU activity in the upper limb exhibits discrete beta bursts that are temporally aligned with cortical beta activity. Notably, beta bursts in the periphery were time-locked to cortical bursts, suggesting strong coordination and synchronisation of bursting across the corticospinal tract. We also found stronger beta synchronisation in the extensor carpi ulnaris compared to the extensor carpi radialis, indicating muscle-specific differences in shared neural drive. These findings provide the first demonstration of beta burst propagation from cortex to upper-limb MUs and show that HDsEMG can reliability detect such events in the upper limb. This work supports the cortical origin and structure of peripheral beta activity and demonstrates its potential as a neurophysiological biomarker for targeting corticospinal dynamics in motor disorders such as Parkinsons disease. Significance StatementWe provide the first evidence of cortical beta bursting in motor unit (MU) activity of forearm extensors across varying force levels. Our results show that MU beta bursting is time-locked to cortical beta bursts, supporting the idea of direct corticospinal transmission in the upper limb. Our findings highlight the value of MU level analysis in understanding beta burst transmission and indicate that burst timing is robust to changes in contraction levels. Unlike traditional bipolar EMG, MU-level analysis offers higher temporal precision and source specificity, enabling the reliable detection of beta bursts in individual muscles. These findings demonstrate a robust cortical-peripheral beta relationship during isometric contractions and reinforces the utility of HDsEMG for investigating burst dynamics and refining neurophysiological biomarkers.

neuroscience↗

bioRxiv2024

Anatomical Abnormalities Suggest a Compensatory Role of the Cerebellum in Early Parkinson's Disease

Brain atrophy is detected in early Parkinsons disease (PD) and accelerates over the first few years post-diagnosis. This was captured by multiple cross-sectional studies and a few longitudinal studies in early PD. Yet only a longitudinal study with a control group can capture accelerated atrophy in early PD and differentiate it from healthy ageing. Accordingly, we performed a multicohort longitudinal analysis between PD and healthy ageing, examining subcortical regions implicated in PD pathology, including the basal ganglia, thalamus, corpus callosum (CC), and cerebellum. Longitudinal volumetric analysis was performed on 56 early PD patients and 53 matched controls, with scans collected 2-3 years apart. At baseline, the PD group showed a greater volume in the pallidum, thalamus, and cerebellar white matter (WM), suggesting potential compensatory mechanisms in prodromal and early PD. After 2-3 years, accelerated atrophy in PD was observed in the putamen and cerebellar WM. Interestingly, healthy controls - but not PD patients - demonstrated a significant decline in Total Intracranial Volume (TIV), and atrophy in the thalamus and mid-CC. Between-group analysis revealed more severe atrophy in the right striatum and cerebellar WM in PD, and in the mid-posterior CC in controls. Using CEREbellum Segmentation (CERES) for lobule segmentation on the longitudinal PD cohort, we found a significant decline in the WM of non-motor regions in the cerebellum, specifically Crus I and lobule IX. Our results highlight an initial increase in cerebellar WM volume during prodromal PD, followed by significant degeneration over the first few years post-diagnosis.

neuroscience↗

bioRxiv2023

Modulatory Effect of Levodopa on the Basal Ganglia-Cerebellum Connectivity in Parkinson's Disease

Levodopa has remained the mainstay of medical therapy for Parkinsons disease since its development in the 1980s. However, long-term medication use is associated with declining clinical efficacy and the emergence of motor complications. Unveiling the effects of levodopa on brain functional reorganisation at a relatively early treatment phase is therefore imperative to inform the optimisation of Parkinsons therapeutics. In this study, we comprehensively investigated levodopas modulation on the resting-state functional connectivity in the cortico- basal ganglia-cerebellum system at regional and network levels, with dual cross-sectional and longitudinal designs. The data was extracted from the Parkinsons Progression Marker Initiative (PPMI) dataset. The cross-sectional patient groups comprised 17 Parkinsons patients on stable levodopa medication and 15 drug-naive patients, while the longitudinal set included 14 Parkinsons patients measured at both drug-naive and levodopa-medicated conditions. With nodes defined across cortical, basal ganglia, and cerebellar networks, we conducted univariate comparisons of the internodal connectivity strength between the medication conditions using nonparametric permutation. At the network level, we computed multivariate combinations of individual connections within and between the networks, followed by an assessment of their discriminative capabilities on patients medication classes using supervised machine learning. The univariate seed-based approach showed no statistically significant effect of levodopa in either dataset. However, the network connectivity pattern between basal ganglia and the cerebellum displayed a robust classification power in the longitudinal dataset and a similar trend was observed in the cross-sectional. The role of the cerebellum is often overlooked in previous functional integration investigations of Parkinsons disease and levodopa effects. Considering the recent evidence suggesting the bidirectional communications between the cerebellum and basal ganglia networks, our study provides further insight into the importance of inter-network functional connectivity in Parkinsons, as well as in the functional and plastic processes following levodopa medication.

neuroscience↗