Biology subjects

Simoneau, M.

Publications and source records attributed to Simoneau, M..

8 recordsLinked to original sources

bioRxiv2026

Vestibular control of posture deviates from Weber's law in response to electrical vestibular stimulation

Standing balance relies on the continuous detection of body motion across a wide range of amplitudes and frequencies. According to Weber's law, sensory discrimination should degrade in proportion to stimulus amplitude, yet vestibular self-motion perception deviates from this prediction. Whether this deviation extends to the vestibular control of posture remains unknown. To test this hypothesis, we delivered amplitude-increasing electrical vestibular stimulation (EVS, 0-2 mA) at four frequencies (0.1, 0.2, 0.5, and 1 Hz) to 10 healthy young adults, and quantified balance discrimination thresholds (DTs) from the gain and inter-trial variability of the lateral ground reaction force, using signal detection theory. Balance control DTs increased sublinearly with EVS amplitude at all frequencies, deviating from Weber's law. Both balance-correcting response gain and variability accounted for this deviation: gain decreased more slowly than the strictly inverse relationship that would have alone produced strict adherence to Weber's law, while variability exhibited an initial increase followed by saturation at higher EVS amplitudes, a signal-dependent structure necessary to reproduce the observed DT pattern. EVS frequency modulated the shape of this deviation but affected neither overall DT nor the signal-to-noise ratio of the balance-correcting response, which instead remained similar across frequencies. This study revealed a particular property of postural control discrimination by extending the psychophysical and neural deviations from Weber's law previously reported for vestibular perception. Overall, these results provide a better understanding of the balance control discrimination process and provide potential additional assessment criteria for vestibular impairments.

neuroscience↗

bioRxiv2026

Athletes exposed to uncommon vestibular stimulation strengthen their tactile-neural pathway

Strikingly, highly trained athletes engaged in vertiginous activities (e.g., dance and slacklining) and patients with bilateral vestibular loss show a similar pattern of neural plasticity, likely resulting from reduced vestibular sensory processes. However, unlike patients, these athletes show no balance impairments, quite the opposite. This suggests that the attenuation of vestibular processing represents an adaptive recalibration to excessive vestibular stimulation rather than a sign of dysfunction. Concurrently, tactile processing increases as vestibular processing attenuates. Our findings indicate that effective adaptation extends beyond simple tactile compensation: it involves a strengthened tactile-brain pathway. Indeed, following unexpected base-of-support translations, the coupling between plantar shear forces (i.e., a proxy of plantar sole tactile afferents) and cortical responses over the somatosensory areas was markedly enhanced in Athletes. Cross-correlation analysis revealed stronger (r = 0.71) and faster (36 ms) tactile-brain coupling in Athletes (n = 25) compared with age- and gender-matched Controls (n = 18). This enhancement occurred within the first 180 ms following translation, that is, during the critical early phase of skin-surface interaction. Notably, artistic swimmers, who undergo intense vestibular stimulation in a weightless underwater environment without balance equilibrium constraints, also exhibit enhanced tactile-brain coupling. This suggests that strengthening the tactile-brain coupling is not merely a byproduct of balance expertise, but rather a broader adaptive response to sustained vestibular stimulation. Multimodal neurons integrating vestibular and somatosensory inputs, such as those in the somatosensory cortex and thalamus, may increase their responsiveness to foot tactile afferents when vestibular inputs become excessive. In such contexts, the somatosensory system may assume a dominant role in providing gravity-related information for balance control.

neuroscience↗

bioRxiv2025

Neuromuscular, Cardiovascular, and Cognitive Fatigue in Motor Learning: A Systematic Review

BackgroundFatigue is multifactorial and task-dependent, arising from the interplay between performance and perceived fatigability. Fatigue-related changes in sensorimotor control and neural activity may alter skill acquisition and retention. ObjectiveTo synthesize behavioral and neurophysiological evidence on how cognitive, cardiovascular, and neuromuscular fatigue influence motor-skill acquisition, consolidation/retention, and transfer. MethodsA systematic search was conducted within PubMed, Web of Science, and Embase. Thirty-four studies (39 experiments) met inclusion criteria (fatigue effects on motor learning in non-disabled participants). Data were extracted on fatigue protocol, learning taxonomy, learning stage (acquisition vs. retention/transfer), interval, and neurophysiology. Methodological quality was appraised with a tailored Downs & Black checklist. ResultsDuring acquisition, 64% of experiments reported impairments under fatigue, particularly for visuomotor precision and fine force control; 10% found facilitation (often after cardiovascular exertion or high cognitive load); 15% were neutral; 10% inconclusive. Retention was tested in a fresh state and in a fatigue state in 34 experiments and 6 experiments, respectively. Results during retention tests were relatively variable, depending on fatigue protocols. Neurophysiological measures were scarce (EEG/TMS in only four studies), and very few studies considered the effects of personal factors such as age or sex. ConclusionsFatigue does not uniformly impair motor learning. Neuromuscular fatigue typically hampers acquisition and sometimes retention, while cardiovascular exertion can transiently prime plasticity and enhance consolidation. Evidence for cognitive fatigue is limited and inconsistent. Future work should use longer retention windows, state-matched testing, and integrated neurophysiology to clarify mechanisms and guide training under fatigue.

neuroscience↗

bioRxiv2024

Guided by touch: Tactile Cues in Hand Movement Control

Traditionally, touch is associated with exteroception and is rarely considered a relevant sensory cue for controlling movements in space, unlike vision. We developed a technique to isolate and evaluate tactile involvement in controlling sliding finger movements over a surface. Young adults traced a 2D shape with their index finger under direct or mirror-reversed visual feedback to create a conflict between visual and somatosensory inputs. In this context, increased reliance on somatosensory input compromises movement accuracy. Based on the hypothesis that tactile cues contribute to guiding hand movements, we predicted poorer performance when the participants traced with their bare finger compared to when their tactile sensation was dampened using a smooth finger splint. The results supported this prediction. EEG source analyses revealed smaller current in the presumed somatosensory cortex during sensory conflict, but only when the finger directly touched the surface. This finding suggests the gating of task-irrelevant somatosensory inputs. Together, our results emphasize touchs involvement in movement control, challenging the notion that vision predominantly governs goal-directed hand or finger movements.

neuroscience↗

bioRxiv2022

Seeing our hand or a tool during visually-guided actions: different effects on the somatosensory and visual cortices

The processing of proprioceptive information in the context of a conflict between visual and somatosensory feedbacks deteriorates motor performance. Previous studies have shown that seeing ones hand increases the weighting assigned to arm somatosensory inputs. In this light, we hypothesized that the sensory conflict, when tracing the contour of a shape with mirror-reversed vision, will be greater for participants who trace with a stylus seen in their hand (Hand group, n=17) than for participants who trace with the tip of rod without seen their hand (Tool group, n=15). Based on this hypothesis, we predicted that the tracing performance with mirror vision will be more deteriorated for the Hand group than for the Tool group, and we predicted a greater gating of somatosensory information for the Hand group to reduce the sensory conflict. The participants of both groups followed the outline of a shape in two visual conditions. Direct vision: the participants saw the hand or portion of a light 40 cm rod directly. Mirror Vision: the hand or the rod was seen through a mirror. We measured tracing performance using a digitizing tablet and the cortical activity with electroencephalography. Behavioral analyses revealed that the tracing performance of both groups was similarly impaired by mirror vision. However, contrasting the spectral content of the cortical oscillatory activity between the Mirror and Direct conditions, we observed that tracing with mirror vision resulted in significantly larger alpha (8-12 Hz) and beta (15-25 Hz) powers in the somatosensory cortex for participants of the Hand group. The somatosensory alpha and beta powers did not significantly differ between Mirror and Direct vision conditions for the Tool group. For both groups, tracing with mirror vision altered the activity of the visual cortex: decreased alpha power for the Hand group, decreased alpha and beta power for the Tool group. Overall, these results suggest that seeing the hand enhanced the sensory conflict when tracing with mirror vision and that the increase of alpha and beta powers in the somatosensory cortex served to reduce the weight assigned to somatosensory information. The increased activity of the visual cortex observed for both groups in the mirror vision condition suggests greater visual processing with increased task difficulty. Finally, the fact that the participants of the Tool group did not show better tracing performance than those of the Hand group suggests that tracing deterioration resulted from a sensorimotor conflict (as opposed to a visuo-proprioceptive conflict).

neuroscience↗

bioRxiv2022

Cortical facilitation of somatosensory inputs using gravity-related tactile information in patients with bilateral vestibular loss

A few years after their bilateral vestibular loss, individuals usually show a motor repertoire that is almost back to normal. This recovery is thought to involve an up-regulation of the visual and proprioceptive information that compensates for the lack of vestibular information. Here, we investigated whether plantar tactile inputs, which provide body information relative to the ground and to the Earth-vertical, contribute to this compensation. More specifically, we tested the hypothesis that somatosensory cortex response to electric stimulation of the plantar sole in standing adults will be greater in patients (n = 10) with bilateral vestibular loss than in an aged-matched healthy group (n = 10). Showing significant greater somatosensory evoked potentials (i.e., P1N1) in patients than in controls, the electroencephalographic recordings supported this hypothesis. Furthermore, we found evidence that increasing the differential pressure between both feet, by adding a 1 kg mass at each pending wrist, enhanced the internal representation of body orientation and motion relative to a gravitational reference frame. The large decreased in alpha/beta power in the right posterior parietal cortex (and not in the left) is in line with this assumption. Finally, our behavioral analyses showed smaller body sway oscillations for patients, likely originated from a tactile-based control strategy. Conversely, healthy subjects showed smaller head oscillations suggesting a vestibular-based control strategy, the head serving as a reference for balance control. HighlightsO_LISomatosensory cortex excitability is greater in patients with bilateral vestibular loss than in aged-matched healthy individuals C_LIO_LITo control balance, healthy individuals "locked" the head while vestibular patients "locked" their pelvis C_LIO_LIFor vestibular patients, increasing loading/unloading mechanism enhances the internal representation of body state in the posterior parietal cortex C_LI

neuroscience↗

bioRxiv2021

On the dynamics of spatial updating

Most of our knowledge on the human neural bases of spatial updating comes from fMRI studies in which recumbent participants moved in virtual environments. As a result, little is known about the dynamic of spatial updating during real body motion. Here, we exploited the high temporal resolution of electroencephalography (EEG) to investigate the dynamics of cortical activation in a spatial updating task where participants had to remember their initial orientation while they were passively rotated about their vertical axis in the dark. After the rotations, the participants pointed towards their initial orientation. We contrasted the EEG signals with those recorded in a control condition in which participants had no cognitive task to perform during body rotations. We found that the amplitude of the P1N1 complex of the rotation-evoked potential (RotEPs) (recorded over the vertex) was significantly greater in the Updating task. The analyses of the cortical current in the source space revealed that the main significant task-related cortical activities started during the N1P2 interval (136-303 ms after rotation onset). They were essentially localised in the temporal and frontal (supplementary motor complex, dorsolateral prefrontal cortex, anterior prefrontal cortex) regions. During this time-window, the right superior posterior parietal cortex (PPC) also showed significant task-related activities. The increased activation of the PPC became bilateral over the P2N2 component (303-470 ms after rotation onset). In this late interval, the cuneus and precuneus started to show significant task-related activities. Together, the present results are consistent with the general scheme that the first task-related cortical activities during spatial updating are related to the encoding of spatial goals and to the storing of spatial information in working memory. These activities would precede those involved in higher order processes also relevant for updating body orientation during rotations linked to the egocentric and visual representations of the environment.

paleontology↗

bioRxiv2019

Balance Control Mechanisms Do Not Benefit From Successive Stimulation Of Different Sensory Systems

In humans, to reduce deviations from a perfect upright position, information from various sensory cues is combined and continuously weighted based on its reliability. Combining noisy sensory information to produce a coherent and accurate estimate of body sway is a central problem in human balance control. In this study, we first compared the ability of the sensorimotor control mechanisms to deal with altered ankle proprioception or vestibular information (i.e., the single sensory condition). Then, we evaluated whether successive stimulation of difference sensory systems (e.g., Achilles tendon vibration followed by electrical vestibular stimulation, or vice versa) produced a greater alteration of balance control (i.e., the mix sensory condition). Electrical vestibular stimulation (head turned [~]90{degrees}) and Achilles tendon vibration induced backward body sways. We calculated the root mean square value of the scalar distance between the center of pressure and the center of gravity as well as the time needed to regain balance (i.e., stabilization time). Furthermore, the peak ground reaction force along the anteroposterior axis, immediately following stimulation offset, was determined to compare the balance destabilization across the different conditions. In single conditions, during vestibular or Achilles tendon vibration, no difference in balance control was observed. When sensory information returned to normal, balance control was worse following Achilles tendon vibration. Compared to that of the single sensory condition, successive stimulation of different sensory systems (i.e., mix conditions) increased stabilization time. Overall, the present results reveal that single and successive sensory stimulation challenges the sensorimotor control mechanisms differently.

neuroscience↗