Biology subjects

Grospretre, S.

Publications and source records attributed to Grospretre, S..

4 recordsLinked to original sources

bioRxiv2026

Immersive bottle effect: Influence of virtual object simulation on modulation of corticospinal excitability by motor imagery

Motor imagery is a cognitive process that engages the motor system and facilitates motor learning, recovery, and performance. Its effectiveness relies on the activation of corticospinal pathways, which can be modulated by action observation. This study investigated whether observing graspable objects facilitates corticospinal excitability during motor imagery, and whether immersive virtual reality amplifies this effect. Twelve healthy adults of either sex completed a single session involving six conditions: rest, object observation on a screen or in virtual reality, motor imagery alone, and combined observation with motor imagery. Transcranial magnetic stimulation was used to record motor-evoked potentials from hand and forearm muscles, and fatigue and imagery quality were quantified. Results showed that observing a manipulable object during motor imagery significantly increased corticospinal excitability. This facilitation was strongest when the object was presented in a virtual environment. The effect was muscle-specific, targeting the agonist hand muscle of the imagined action (Abductor Pollicis Brevis), and was more pronounced at the higher stimulation intensity. Fatigue and imagery quality were similar across conditions. These findings indicate that object affordances can prime motor circuits and enhance motor imagery-induced neural activation, with immersive environments further reinforcing this effect. This is the first study demonstrating that combining motor imagery with virtual object observation maximizes corticospinal excitability. This approach may represent a promising tool for rehabilitation and sports training. Further studies should identify the optimal parameters and the neurophysiological markers of cortical modulation for this combination. NEW & NOTEWORTHYUsing transcranial magnetic stimulation with immersive virtual reality, we showed for the first time that observing a virtual object associated with the imagined movement increased corticospinal excitability to a greater extent than motor imagery performed alone.

neuroscience↗

bioRxiv2026

Snipers under stress: mentally simulated motor actions are resistant to acute stress in police officers

Motor imagery (MI) is a sensorimotor process allowing to mentally simulate a motor action and is widely used to enhance performance in domains such as rehabilitation, sport, and professional training. Although MI is increasingly incorporated into stress-management interventions, the reciprocal relationship, that is, the effect of acute stress on MI remains paradoxically poorly understood, particularly in ecologically valid settings. The present study investigated this issue in professional police officers performing physically and mentally a precise handgun manipulation task under graded stress conditions (psychological stress). Fourteen participants (mean age = 36.57 {+/-} 2.10 years) was exposed to controlled, work-related stress scenarios designed to closely reflect real operational demands, while stress markers and temporal features of executed and imagined movements were recorded. Our results clearly indicate that motor imagery was preserved despite significant increases in stress levels, as the temporal characteristics of both executed and imagined movements remained stable across experimental conditions. These findings indicate that MI is resilient to acute psychosocial stress and support its relevance as a reliable training and performance-optimization tool in high-demand occupational settings.

neuroscience↗

bioRxiv2023

Acute effect of transcranial direct current stimulation (tDCS) on postural control of trained athletes: a randomized controlled trial

Transcranial direct current stimulation (tDCS) is used to modulate the brain function in targeted brain areas, and can acutely modulate motor control, such as postural control. While the acute effect of tDCS is well documented on patients, little is still known whether tDCS can alter the motor control of healthy populations with an already high level of motor skills. This study aimed to assess the acute effect of tDCS on postural control of trained athletes. Eighteen parkour practitioners, known for their good balance abilities, were tested on three occasions in the laboratory for each stimulation condition (2 mA ; 20 minutes) - primary motor cortex (M1), prefrontal cortex (dlPFC) and sham (placebo). Postural control was evaluated PRE and POST each stimulation by measuring Center of Pressure (CoP) displacements on a force platform during static conditions (bipedal and unipedal stance). Following M1 stimulation, significant decreases were observed in CoP area in unipedal (P=0.003) and bipedal (P<0.001) stances. As well, the CoP total length was significantly reduced in bipodal (P=0.005) as well as in unipedal stance (P<0.001), only after M1 stimulation. Relative pre-post changes observed after M1 stimulation were negatively correlated to experience in parkour only after unipedal stance (r=0.715, P<0.001), meaning that the more participants were trained the less tDCS was effective. No significant changes were noticed after sham and dlPFC stimulation. These results suggested that the modulation of gait performance in athletes following an acute intervention of tDCS is specific to the targeted brain region, and that more complex postures (such as unipedal stance) were more sensitive to the effect of tDCS according to the level of practice.

neuroscience↗

bioRxiv2019

A cross-species neural integration of gravity for motor optimisation

Recent kinematic results, combined with model simulations, have provided support for the hypothesis that the human brain uses an internal model of gravity to shape motor patterns that minimise muscle effort. Because many different muscular activation patterns can give rise to the same trajectory, here we analyse muscular activation patterns during single-degree-of-freedom arm movements in various directions, which allow to specifically investigating gravity-related movement properties. Using a well-known decomposition method of tonic and phasic electromyographic activities, we demonstrate that phasic EMGs present systematic negative phases. This negativity demonstrates that gravity effects are harvested to save muscle effort and reveals that the brain implements an optimal motor plan using gravity to accelerate downward and decelerate upward movements. Furthermore, for the first time, we compare experimental findings in humans to monkeys, thereby generalising the Effort-optimization strategy across species.

neuroscience↗