Pilotto, A. | bioRxiv Science

bioRxiv2026

Bandpass corticospinal transmission during repetitive TMS revealed by motor unit recordings

We employed a noninvasive high-density surface electromyography (HDsEMG) framework to track spinal motor neuron responses during repetitive transcranial magnetic stimulation (rTMS) and characterize corticospinal transmission of different stimulation frequencies and intensities to the alpha motor neuron pool. Eleven healthy individuals performed isometric thumb flexion at 10% of maximal voluntary contraction while rTMS was delivered over the motor cortex at five frequencies (5, 10, 20, 30, and 50 Hz) and three subthreshold intensities (50%, 60%, and 70% of resting motor threshold). Motor units were decomposed from HDsEMG signals before stimulation and tracked during rTMS. Input-output coupling was quantified using coherence between the rTMS train and individual motor unit spike trains or the cumulative spike train (CST), with shuffled spike trains used as surrogate controls. rTMS inputs were robustly transmitted to spinal motor neurons for all frequencies except 5 Hz, indicating widespread corticospinal coupling. Transmission behaved linearly, with CST output spectra reproducing input frequencies and scaling proportionally with stimulation intensity. The estimated transfer function revealed a bandpass-like profile, with maximal transmission between 10 and 60 Hz. Transmitted inputs also induced oscillatory components in the common synaptic input to motor neurons at stimulation frequency. Simulations indicated that this frequency selectivity emerges from balanced excitatory and inhibitory inputs to the motor neuron pool, with specific synaptic dynamics. These findings demonstrate that corticospinal transmission during rTMS acts as a frequency-selective linear system and provide a framework for assessing and modulating corticospinal pathways, with potential application as tool for tracking disease progression and neurorehabilitation. Highlights- HDsEMG decomposition tracks spinal motor neuron activity during rTMS. - Corticospinal transmission scales with rTMS stimulation intensity. - Corticospinal pathways act as a frequency-selective system. - rTMS transfer function shows maximal transmission at 10-60 Hz. - EPSP-IPSP interactions explain bandpass corticospinal transmission during rTMS.

neuroscience↗

bioRxiv2026

Promoting Healthy Ageing through Choral Training: A 9-Month Multidomain Intervention (MultiMusic) Enhances Neural Processing Speed in Community-Dwelling Older Adults

BackgroundOlder adulthood is often accompanied by declines in auditory processing and cognitive functioning, increasing the risk of reduced autonomy and quality of life. Multidomain lifestyle interventions have shown potential to counteract these changes, and choir-based activities represent a promising approach by simultaneously engaging auditory, cognitive, physical, and social domains. However, evidence regarding their feasibility and neurophysiological impact in community-dwelling older adults, particularly those without formal musical training, remains scarce. MethodsThis 9-month quasi-experimental feasibility study involved 54 community-dwelling older adults (mean age = 72.9 years) with no formal musical background. Participants self-selected into a choir-based intervention group, an active control group engaging in non-musical leisure activities, or a passive control group; however, some participants in the control groups were selected from the waiting list for the choir. Assessments were conducted at baseline and follow-up and included measures of global cognition, cognitive reserve, psychological well-being (Flourishing Scale), multidimensional frailty (Selfy-MPI), music perception, pure-tone audiometry, and auditory evoked potentials recorded using a standardized clinical oddball paradigm. ResultsThe choir-based intervention was feasible in a community setting. At the neurophysiological level, choir participation was associated with a bilateral, significant shortening of the N2-P3 inter-peak latency, indicating faster auditory-cortical processing. Additionally, through explorative analyses multidimensional frailty, as assessed by the Selfy-MPI, showed a significant reduction in individuals engaging in a higher number of activities, irrespective of group allocation. Similarly, psychological well-being revealed a decrease in flourishing scores in the passive control group relative to the choir group. No changes were observed in audiometric thresholds or music perception measures. ConclusionChoir-based multidomain participation is a feasible intervention for community-dwelling older adults without formal musical training and is associated with selective benefits in cognitive reserve, psychological well-being, auditory-cortical processing speed, and multidimensional frailty. These findings provide a foundation for a larger randomized controlled trial aimed at clarifying the cognitive, psychosocial, and neural mechanisms underlying choir-based interventions in ageing. Trial RegistrationThe upcoming trial has been prospectively registered on ClinicalTrials.gov (ID: NCT06767410; registration date: January 9, 2025).

neuroscience↗