Biology subjects

Cattagni, T.

Publications and source records attributed to Cattagni, T..

9 recordsLinked to original sources

bioRxiv2026

Estimates of persistent inward currents in human spinal motor neurons: non-linear and sex-dependent trajectories from young to very old age

The contribution of persistent inward currents (PICs) to spinal motor neurons discharge rate is lower in old compared to young adults. However, whether this difference further progresses at very old age ([≥]80 years) and differs between males and females remains unknown. Thirty young (26 {+/-} 4 years, 15 females), thirty old (72 {+/-} 5 years, 15 females) and twenty-nine very old adults (85 {+/-} 3 years, 15 females) performed isometric dorsiflexion ramp contractions at 20% of maximal voluntary torque. Individual motor unit spike trains were identified from decomposed high-density surface electromyograms of the tibialis anterior. The paired motor unit technique was used to estimate the prolongation effect of PICs ({Delta}F and normalized {Delta}F), and the quasi-geometric approach to estimate neuromodulatory (brace height) and inhibitory pattern (attenuation slope) contributions. {Delta}F was lower in old and very old adults than in young adults, with no difference between old and very old adults regardless of sex. Compared with young adults, normalized {Delta}F was lower in both old and very old males, whereas in females it is only lower in the very old group. Brace height and attenuation slope did not differ across ages or sexes. These findings indicate that age-related changes in spinal motor neuron excitability are established by the seventh decade and do not progress further in healthy active very old adults, following a nonlinear trajectory that may differ between males and females. The absence of age-related differences in the neuromodulatory index does not support a lower monoaminergic drive in older adults.

physiology↗

bioRxiv2026

Recurrent inhibition, not presynaptic inhibition, contributes to the velocity-dependent control of motoneuron output during eccentric contractions

It is well documented that both motoneuron output and the effectiveness of activated Ia afferents to discharge soleus -motoneurons decrease during eccentric (muscle lengthening) contractions. Evidence suggests that these modulations can be explained by recurrent inhibition and greater presynaptic inhibition of Ia afferents. However, the influence of angular velocity on the modulation of the effectiveness of activated Ia afferents to discharge -motoneurons observed during eccentric contractions remains unclear. We investigated the influence of angular velocity on spinal mechanisms involved in the effectiveness of activated Ia afferents to discharge -motoneurons during eccentric plantar flexor contractions using 16 healthy adults. We used both simple and conditioned Hoffmann reflex with different conditioning techniques to assess presynaptic inhibition, heteronymous Ia facilitation and heteronymous recurrent inhibition coupled with electromyography during eccentric contractions of the plantar flexors at three angular velocities. Our results showed that during eccentric contractions, the effectiveness of Ia afferents to discharge -motoneurons was lower at 90{degrees}{middle dot}s-{superscript 1} than 60{degrees}{middle dot}s-{superscript 1} and 20{degrees}{middle dot}s-{superscript 1} angular velocities. A similar velocity-dependent pattern was observed for heteronymous recurrent inhibition, decreasing at 90{degrees}{middle dot}s-{superscript 1} when compared with 60{degrees}{middle dot}s-{superscript 1} and 20{degrees}{middle dot}s-{superscript 1}. In contrast, presynaptic inhibition of Ia afferents was not different between the velocities. These demonstrate a differential influence of angular velocity on spinal recurrent inhibitory mechanisms during eccentric contractions and support distinct functional roles of recurrent and presynaptic inhibition in modulating -motoneurons discharge with increasing movement velocity. The findings provide new insights into the velocity-dependent and mechanism-specific modulation of spinal inhibitory circuits during eccentric contractions. KEY POINTSO_LIDuring eccentric contractions in soleus muscle, the effectiveness of activated Ia afferents to discharge -motoneurones decreases with increasing angular velocity, indicating a velocity-dependent modulation. C_LIO_LIPresynaptic inhibition of Ia afferents does not differ between angular velocities, suggesting that it does not contribute to the observed changes. C_LIO_LIHeteronymous recurrent inhibition from the quadriceps to the soleus increases with angular velocity, indicating that increasing movement velocity promotes a functional reorganization of intermuscular recurrent inhibition. C_LIO_LIThese findings suggest a differential functional role of the two spinal inhibitory mechanisms, indicating that increasing angular velocity primarily influences recurrent postsynaptic inhibition rather than presynaptic inhibition. C_LI

neuroscience↗

bioRxiv2026

Disrupted Inhibitory-Excitatory Balance Underlies Spinal Motoneuron Dysfunction in Incomplete Spinal Cord Injury

Incomplete spinal cord injury disrupts voluntary movement, in part through motoneuron dysfunction, yet the mechanisms underlying this dysfunction remain poorly understood. Using a non-invasive approach to decode the spiking activity of large populations of spinal motoneurons, we quantified the relative contributions of excitatory, inhibitory, and neuromodulatory inputs to motoneuron rate coding after chronic incomplete spinal cord injury. Eighteen participants with incomplete spinal cord injury and 18 age- and sex-matched control participants performed submaximal isometric plantar flexion tasks while high-density surface electromyography was recorded from the soleus and gastrocnemius medialis muscles. Motoneuron firing behaviour was analysed to estimate neuromodulatory drive and the balance between inhibitory and excitatory inputs. Participants with incomplete spinal cord injury exhibited lower rate coding, characterised by lower firing rates at recruitment, lower firing rate modulation, and lower peak firing rates compared with healthy controls. Although estimates of neuromodulatory drive did not differ between groups, individuals with spinal cord injury showed a shift in the inhibition-excitation balance toward greater inhibition compared with controls. Furthermore, increasing inhibitory input through muscle length changes and antagonist tendon vibration modulated motoneuron firing in controls, but not in individuals with incomplete spinal cord injury. Together, these findings suggest that impaired rate coding after incomplete spinal cord injury arises from an altered inhibitory-excitatory balance rather than reduced neuromodulatory drive. Taking advantage of methodological advances to decode spinal motor neuron activity during voluntary contraction, this study identified excessive inhibitory input to spinal motoneurons as a key neural mechanism contributing to muscle weakness and impaired motor function in individuals with incomplete spinal cord injury.

neuroscience↗

bioRxiv2025

Probabilistic inference of Homonymous and Heteronymous Recurrent Inhibition in Human Muscles from Large-Scale Motor Neuron Recordings

Understanding how spinal circuits shape motor neuron behavior during muscle contractions remains a major challenge. Here, we combined large-scale motor unit recordings with simulation-based inference to generate probabilistic estimates of homonymous and heteronymous recurrent inhibition, a key spinal circuit that has remained largely inaccessible during natural voluntary contractions. We constructed synchronization cross-histograms from motor neuron spike trains and extracted features representative of recurrent inhibition. Because these features are also influenced by higher-frequency components of common synaptic input, we developed a simulation-based inference framework to disentangle these effects. Following validation, we applied this framework to experimental data from six muscles at two contraction intensities, revealing previously uncharacterized muscle-and intensity-dependent patterns: recurrent inhibition decreased with contraction intensity in most muscles but increased in the vastus lateralis and medialis. The pipeline is openly available and designed for reuse on comparable datasets and for adaptation to diverse experimental contexts, including other spinal circuits. TeaserLarge-scale motor-unit recordings enable in-vivo probabilistic mapping of spinal recurrent inhibition.

neuroscience↗

bioRxiv2025

Diurnal Modulation of Persistent Inward Current Contribution to Spinal Motor Neuron Behaviour

Despite the critical role of persistent inward currents (PICs) in modulating motor neuron output, and thus neuromuscular performance, it remains unknown whether their contribution to motor neuron discharge behaviour varies throughout the day. This study aimed to determine whether PIC-related effects on motor neuron activity during submaximal dorsiflexion tasks differ between the early morning and late afternoon. Eighteen healthy adults (4 females; 27.4{+/-}5.6 years) performed triangular isometric contractions at two time-points: early morning (7:00-8:30 a.m.) and late afternoon (5:00-7:30 p.m.). Two conditions were tested: (1) a relative condition, where the target force corresponded to 40% of the maximal voluntary force (MVF) measured during that session, and (2) an absolute condition, where the target force was 40% of the MVF recorded during the first session. High-density surface electromyography signals were recorded from the tibialis anterior and decomposed into motor unit spike trains. The prolongation effect of PICs, estimated via {Delta}F, was significantly greater in the late afternoon in both the relative and absolute force conditions. The amplification effect of PICs, estimated by the acceleration phase of the discharge trajectory, was also higher in the late afternoon, but only in the relative force condition. No time-of-day differences were found for brace height, while attenuation was reduced in the late afternoon in the relative force condition. Collectively, these findings provide evidence for a diurnal modulation of the influence of PICs on motor neuron discharge behaviour, likely mediated by reduced inhibitory input in the late afternoon rather than by changes in neuromodulatory drive. Key pointsO_LI- Human neuromuscular performance fluctuates throughout the day, with higher force output typically observed in the late afternoon. C_LIO_LI- While circadian effects on peripheral determinants of muscle function (e.g., muscle- tendon properties, metabolic efficiency) are well documented, the neural mechanisms underlying these diurnal variations remain poorly understood. C_LIO_LI- Persistent inward currents (PICs) play a critical role in regulating motor neuron behaviour, yet their potential diurnal modulation has not been previously investigated. C_LIO_LI- Our results provide novel evidence for a diurnal modulation of the influence of PICs on motor neuron discharge behaviour, likely mediated by reduced inhibitory input in the late afternoon rather than by changes in neuromodulatory drive. C_LIO_LI- These findings suggest that intrinsic motor neuron excitability (and therefore spinal gain modulation) fluctuates across the day. C_LI

neuroscience↗

bioRxiv2025

Expert drummers replicate neuromechanical signatures of physiological tremor at extreme movement frequencies.

This study investigates the neuromechanical characteristics associated with expert drummers ability to achieve unilateral ankle oscillation frequencies of up to 10 Hz, surpassing known limits for lower-body movements. Eighteen experienced drummers performed trials at various frequencies, using a protocol combining H-reflex measurement, motion analysis, and electromyography. Our findings closely parallel neuromechanical signatures observed in ankle tremors, with an average movement frequency of 6.3 Hz (SD: 0.5 Hz), and a modulation range of 5.5-7.3 Hz. Oscillatory behavior may result from the interplay between muscle-tendon mechanics and stretch reflex loops. At 6.3 Hz, soleus activation lasts 56.2 ms, shortening by 2.5 ms/Hz (p < 0.001), while tibialis anterior activation lasts 52.7 ms, decreasing by 5.3 ms/Hz (p < 0.001). The latency between ankle dorsiflexion and soleus activation is 48.5 ms at 6.3 Hz, matching the short-latency stretch reflex, and decreases by 11 ms/Hz (p<0.001). Limiting factors for the drummers maximal frequency are soleus and tibialis anterior co-activation, reducing ankle movement, and high levels of activation in hip and back muscles, associated with discomfort and pain. Drummers with higher maximal frequencies (above 7.5 Hz, n = 6) show shorter tibialis anterior activation durations (34.3 ms vs. 53.2 ms, p = 0.0013) and reduced tensor fascia latae activation (6.2% vs. 21.0%, p = 0.0135). These findings highlight phenomenological similarities between the ankle technique and physiological tremors, in terms of neuromechanical timing and oscillatory patterns. Precise tibialis anterior timing and relaxed proximal muscle activation are critical for performance, while injury prevention strategies remain essential. Significance StatementThis study provides a neuromechanical analysis of expert metal drummers producing exceptionally high-frequency ankle movements--up to 10 Hz--that surpass known limits for lower-body movements, and draws parallels with physiological action tremors. By comparing their motor patterns to those reported in tremor literature, this work highlights the role of neuromuscular timing and mechanical adaptations, such as stretch reflex dynamics and muscle-tendon interactions. The findings demonstrate that precise tibialis anterior timing and relaxed proximal muscles are critical for performance, while stabilization demands increase the risk of musculoskeletal disorders in the lower back and hips. These insights bridge performance science, biomechanics, and injury prevention, offering valuable perspectives for optimizing high-frequency movements in music, sports, and rehabilitation.

physiology↗

bioRxiv2024

Muscle length modulates recurrent inhibition and post-activation depression differently according to contraction type

It is well documented that, in soleus, motoneuron output and the effectiveness of activated Ia afferents to discharge -motoneurons both decrease during eccentric contractions. Evidence suggests that these regulations can be explained by (1) recurrent inhibition and (2) greater post-activation depression by primary afferent depolarization. However, the influence of muscle length on the regulation of the effectiveness of Ia afferents to discharge -motoneurons observed during eccentric contractions remains unclear. We conducted a study on 16 healthy young individuals. We used simple and conditioned Hoffmann reflex with different conditioning techniques such as paired H reflex, D1 method and heteronymous Ia facilitation coupled with electromyography during eccentric, isometric and concentric contractions at long, intermediate and short soleus muscle lengths. Our results confirm that during eccentric contraction the effectiveness of Ia afferents to discharge U-motoneurons decreases only at intermediate and short muscle lengths but is similar between all contraction types at long muscle length. Findings are similar for recurrent inhibition. Post-activation depression is significantly more pronounced during eccentric contractions compared with isometric and concentric contractions at long muscle length. Our analysis also shows that recurrent inhibition and post-activation depression are greater at long muscle length compared with short muscle length, whatever the contraction type. These new findings demonstrate an important influence of muscle length on the activity of spinal regulatory mechanisms and the effectiveness of activated Ia afferents to discharge -motoneurons during eccentric contractions.

neuroscience↗

bioRxiv2024

Flexible Control of Motor Units: Is the Multidimensionality of Motor Unit Manifolds a Sufficient Condition?

Understanding flexibility in the neural control of movement requires identifying the distribution of common inputs to the motor units. In this study, we identified large samples of motor units from two lower limb muscles: the vastus lateralis (VL; up to 60 motor units/participant) and the gastrocnemius medialis (GM; up to 67 motor units/participant). First, we applied a linear dimensionality reduction method to assess the dimensionality of the manifolds underlying the motor unit activity. We subsequently investigated the flexibility in motor unit control under two conditions: sinusoidal contractions with torque feedback, and online control with visual feedback on motor unit firing rates. Overall, we found that the activity of GM motor units was effectively captured by a single latent factor defining a unidimensional manifold, whereas the VL motor units were better represented by three latent factors defining a multidimensional manifold. Despite this difference in dimensionality, the recruitment of motor units in the two muscles exhibited similarly low levels of flexibility. Using a spiking network model, we tested the hypothesis that dimensionality derived from factorization does not solely represent descending cortical commands but is also influenced by spinal circuitry. We demonstrated that a heterogeneous distribution of inputs to motor units, or specific configurations of recurrent inhibitory circuits, could produce a multidimensional manifold. This study clarifies an important debated issue, demonstrating that while motor unit firings of a non-compartmentalised muscle can lie in a multidimensional manifold, the central nervous system may still have limited capacity for flexible control of these units. Key pointsO_LITo generate movement, the central nervous system distributes both excitatory and inhibitory inputs to the motor units. C_LIO_LIThe level of flexibility in the neural control of these motor units remains a topic of debate with significant implications for identifying the smallest unit of movement control. C_LIO_LIBy combining experimental data and in silico models, we demonstrated that the activity of a large sample of motor units from a single muscle can be represented by a multidimensional linear manifold; however, these units show very limited flexibility in their recruitment. C_LIO_LIThe dimensionality of the linear manifold may not directly reflect the dimensionality of descending inputs but could instead relate to the organisation of local spinal circuits. C_LI

neuroscience↗

bioRxiv2023

Estimates of persistent inward currents in lower limb muscles are not different between inactive, resistance-trained and endurance-trained young individuals

Persistent inward currents (PICs) increase the intrinsic excitability of -motoneurons. The main objective of this study was to determine whether estimates of -motoneuronal PIC magnitude is influenced by chronic endurance and resistance training. We also aimed to investigate whether there is a relationship in the estimates of -motoneuronal PIC magnitude between muscles. Estimates of PIC magnitude were obtained in three groups of young individuals: resistance-trained (n=12), endurance-trained (n=12), and inactive (n=13). We recorded high-density surface electromyography (HDsEMG) signals from tibialis anterior, gastrocnemius medialis, soleus, vastus medialis, and vastus lateralis. Then, signals were decomposed with convolutive blind source separation to identify motor units spike trains. Participants performed triangular isometric contractions to a peak of 20% of their maximum voluntary contraction. A paired-motor-unit analysis was used to calculate {Delta}F, which is assumed to be proportional to PIC magnitude. Despite the substantial differences in physical training experience between groups, we found no differences in {Delta}F, regardless of the muscle. Significant correlations of estimates of PICs magnitude were found between muscles of the same group (VL-VM, SOL-GM). Only one correlation (out of 8) between muscles of different groups was found (GM and TA). Overall, our findings suggest that estimates of PIC magnitude in the lower limb muscles are not influenced by physical training experience in healthy young individuals. They also suggest muscle-specific and muscle group-specific regulations of the diffuse monoamine inputs.

neuroscience↗