Biology subjects

Abbagnano, E.

Publications and source records attributed to Abbagnano, E..

3 recordsLinked to original sources

bioRxiv2026

Neurofeedback Training on Motor Cancellation Enhances Peripheral but not Cortical Beta Band Oscillations

Beta oscillations (13-30 Hz) are a prominent sensorimotor neural rhythm and an important biomarker in neurorehabilitation. These oscillations propagate along the corticospinal pathway and are expressed in the discharge patterns of spinal motor neurons, enabling the assessment of corticomuscular coupling. Moreover, peripheral beta band oscillations have recently emerged as a potential control signal for motor augmentation interfaces. However, it remains unclear whether peripheral beta activity simply reflects cortical oscillations or is partly shaped by peripheral mechanisms, and to what extent it can be voluntarily controlled. To address these questions, we developed a 10-day neurofeedback protocol in which participants learned to up-regulate peripheral beta band activity. Subjects were trained to exploit movement cancellation, a behaviour naturally associated with increased cortical and muscle beta band activity, as a two-state strategy to voluntarily modulate peripheral beta band power. Each session included a guided familiarization phase based on a GO/NO-GO task, in which participants familiarized with movement cancellation through guided visual cues, followed by an asynchronous control phase in which they self-initiated the same strategy without external guidance to increase peripheral beta band activity in a target window. Participants progressively improved their ability to voluntarily modulate peripheral beta band activity. Peripheral beta band power during movement cancellation increased significantly across training days in both the familiarization and asynchronous control phases. Intramuscular coherence in the beta band also increased, indicating enhanced common synaptic input to the motor neuron pool in this band. In contrast, cortical beta power and corticomuscular coherence remained unchanged. Together, these findings demonstrate that peripheral beta band activity is a dynamic neural feature that can be voluntarily shaped through training, supporting its potential as a non-invasive control signal for future neurorehabilitation and motor augmentation technologies.

bioengineering↗

bioRxiv2026

High-frequency common inputs entrain motoneuron subpopulations differently

Spinal motoneuron (MN) pools behave as linear systems that transmit common synaptic input to muscles. However, MNs are biophysically heterogeneous and intrinsically nonlinear. How different MN subpopulations integrate and transmit high-frequency inputs remains poorly understood, partly because conventional analyses treat the MN pool as a single functional system rather than examining subpools with different firing rates. Here, we addressed this gap using a combination of computational simulations and human MN recordings. Simulations of MNs receiving a common synaptic input at varying frequencies showed that MNs firings become phase-locked to input oscillations when the input frequency approximates the neurons firing rate or its harmonics. We refer to this frequency-dependent synchronization as entrainment. Importantly, this subpool-specific effect was masked when MN activity was analysed at the whole-pool level. Because entrained MNs effectively sample the input at their firing instants, we developed a MN-firing locked method that uses individual MN firings as endogenous triggering events for peristimulus frequencygrams across the pool. In simulations, this method revealed entrainment-driven firing rate modulations across MN subpools. We then applied this MN-firing locked method to MNs decomposed from high-density surface electromyography recordings obtained during isometric contractions in healthy individuals. We found that faster-firing MNs exhibited larger transient firing rate increases, time-locked to slower MN activity. Furthermore, these modulations correlated with common input in the alpha and beta bands implicating high frequency common input as the driving source. Together, these findings demonstrate that MN nonlinearities generate heterogeneous, frequency-dependent dynamics that remain hidden in conventional pool-level analyses.

neuroscience↗

bioRxiv2025

Projection of Cortical Beta Band Oscillations to a Motor Neuron Pool Across the Full Range of Recruitment

Cortical beta band oscillations (13-30 Hz) are associated with sensorimotor control, but their precise role remains unclear. Evidence suggests that for low-threshold motor neurons, these oscillations are conveyed to muscles via the fastest corticospinal fibers. However, their transmission to motor neurons of different sizes may vary due to differences in the relative strength of corticospinal and reticulospinal projections across the motor neuron pool. Consequently, it remains uncertain whether corticospinal beta transmission follows similar pathways and maintains consistent strength across the entire motor neuron pool. To investigate this, we examined beta activity in motor neurons innervating the tibialis anterior muscle across the full range of recruitment thresholds in a study involving 12 participants of both sexes. We characterized beta activity at both the cortical and motor unit levels while participants performed contractions from mild to submaximal levels. Corticomuscular coherence remained unchanged across contraction forces after normalizing for the net motor unit spike rate, suggesting that beta oscillations are transmitted with uniform strength to motor neurons, regardless of size. To further explore beta transmission, we estimated corticospinal delays using the cumulant density function, identifying peak correlations between cortical and muscular activity. Once compensated for variable peripheral axonal propagation delay across motor neurons, the corticospinal delay remained stable, and its value (approximately 14 ms) indicated projections through the fastest corticospinal fibers for all motor neurons. These findings demonstrate that corticospinal beta band transmission is determined by the fastest pathway connecting in the corticospinal tract, projecting uniformly across the entire motor neuron pool.

bioengineering↗