Biology subjects

Baudry, S.

Publications and source records attributed to Baudry, S..

4 recordsLinked to original sources

bioRxiv2026

Recurrent inhibition crosses the spinal cord midline in humans

Recurrent inhibition is known to modulate motoneuron output within an active motor pool, but it is unclear whether Renshaw cells receive projections from a contralateral pathway. Using intramuscular single motor unit recordings in humans, we demonstrated that electrical activation of the contralateral quadriceps motor axons elicits a robust decrease in soleus motor unit discharge rate, consistent with the characteristic features of recurrent inhibition. The duration of the inhibition scaled with motor unit firing rates and exhibited substantial interindividual variability. To uncover the underlying circuitry, we developed a biophysically grounded spiking network model constrained by individual experimental data. The model reproduced the observed contralateral inhibitory dynamics only when incorporating a polysynaptic commissural pathway mediated by V3-like interneurons. Model-based inference further revealed that intrinsic motoneuron properties critically shape the duration of inhibition. Together, these findings provide the first evidence for a commissural pathway influencing human spinal recurrent inhibitory networks, revealing a previously unrecognized mechanism that may contribute to bilateral motor coordination.

neuroscience↗

bioRxiv2026

Facing pain is effortful: key role of the supplementary motor area and anterior midcingulate cortex

Pain captures attention and interferes with executive and motor processes. In the presence of pain, increasing effort may represent a compensatory mechanism to counteract pain-related disruption and maintain task performance. In this preregistered fMRI study, we investigated neural mechanisms underlying preserved task performance during pain and increased perceived effort. Forty right-handed participants performed a visuomotor force-matching task consisting of isometric handgrip contractions at a low and high force levels under individually calibrated painful or non-painful thermal stimulation. Thermal stimulation was applied to the left forearm, and participants rated the intensity of perceived effort after each isometric contraction. Maintaining task performance under pain was associated with increased perceived effort and recruited brain regions involved in pain modulation and cognitive control. Region-of-interest analysis showed perceived effort was consistently linked to decreased anterior midcingulate cortex activity, whereas supplementary motor area contributions varied depending on its role in motor execution or pain processing. Across experimental condition, motor, pain-modulatory and cognitive-control regions were associated with effort perception. Independently of condition, effort perception was modulated by ventromedial prefrontal cortex and ventral striatum. These findings indicate that effort perception is a complex phenomenon reflecting brain activity within areas involved in motor, executive and valuation processes. Significance StatementThis study advances our understanding of the neural mechanisms underlying task performance under pain and increased effort perception. Brain activity was measured during a visuomotor force-matching task performed in the presence or absence of pain. By contrasting task-related activity between painful and non-painful conditions, we identified regions associated with cognitive control and pain modulation involved in preserving task performance under pain. By correlating activity in regions of interest with ratings of perceived effort, we demonstrated the involvement of the supplementary motor area and midcingulate cortex in effort perception. These findings suggest that additional neural resources are recruited to maintain performance during pain and that the supplementary motor area and midcingulate cortex contribute to heightening the effort experienced.

neuroscience↗

bioRxiv2026

Maintaining performance under pain is effortful: experimental and computational evidence

Pain creates a competing demand on attention, though its impact on performance remains debated. Motivational intensity theory predicts that resource reallocation can preserve output until motivational or capacity limits are reached. Forty adults took part in two preregistered experiments. They completed parallel cognitive (choice reaction, n=20) and motor (isometric hand grip, n=20) tasks at three difficulty levels while receiving warm, low, or high pain heat stimulation on the opposite forearm. Across both domains, participants maintained performance despite painful stimulation. This preservation, however, relied on increased effort mobilization: perceived effort rose with pain intensity, while pain perception decreased during motor and cognitive task execution. Trial wise computational modelling revealed that perceived effort was better predicted by subjective pain experience than by stimulus temperature, supporting a compensatory regulatory mechanism. Thus, maintained performance under pain reflects active resource allocation via effort, generalizable across cognitive and motor domains, but achieved at the cost of increased perceived effort.

neuroscience↗

bioRxiv2024

Estimation of the Achilles tendon twist in vivo by individual triceps surae muscle stimulation

The Achilles tendon (AT) is comprised of three distinct subtendons, each arising from the one of the three heads of the triceps surae muscles: gastrocnemius medialis (GM), gastrocnemius lateralis (GL) and soleus (SOL). These subtendons exhibit a twisted structure, classified as low (Type I), medium (Type II), and high (Type III) twist, based on cadaveric studies. Nevertheless, the in-vivo investigation of AT twist is notably scarce, resulting in a limited understanding of its functional significance. The aim of this study was to give insights into the complex 3D AT structure in vivo. 30 healthy participants underwent individual stimulation of each of the triceps surae muscles at rest with the foot attached to the pedal of an isokinetic dynamometer. Ultrasound images were captured to concomitantly examine the displacement of the superficial, middle and deep AT layers. SOL stimulation resulted in the highest AT displacement followed by GM and GL stimulation. Independent of the muscle stimulated, non-uniformity within the AT was observed with the deep layer exhibiting more displacement compared to the middle and superficial layers, hence important inter-individual differences in AT displacement were noticeable. By leveraging these individual displacement patterns during targeted stimulations in conjunction with cadaveric twist classifications providing insights into the area of each specific subtendon, our classification identified 19 subjects with a low and 11 subjects with a high AT twist. More research is needed to understand the complexity of the AT twisted structure in vivo to further understand its effect on AT properties and behaviour.

physiology↗