Sudden Perturbation Research Articles

Observation of nonlinear response and Onsager regression in a photon Bose-Einstein condensate

The quantum regression theorem states that the correlations of a system at two different times are governed by the same equations of motion as the single-time averages. This provides a powerful framework for the investigation of the intrinsic microscopic behaviour of physical systems by studying their macroscopic response to a controlled external perturbation. Here we experimentally demonstrate that the two-time particle number correlations in a photon Bose-Einstein condensate inside a dye-filled microcavity exhibit the same dynamics as the response of the condensate to a sudden perturbation of the dye molecule bath. This confirms the regression theorem for a quantum gas, and, moreover, demonstrates it in an unconventional form where the perturbation acts on the bath and only the condensate response is monitored. For strong perturbations, we observe nonlinear relaxation dynamics which our microscopic theory relates to the equilibrium fluctuations, thereby extending the regression theorem beyond the regime of linear response.

Electromagnetically induced gratings created by extremely short non-overlapping pulses of light in a three-level resonant medium

In a fixed spectral range, single- and half-cycle electromagnetic pulses have the shortest duration. Half-cycle pulses are promising tools for ultrafast control of quantum systems. Previously, the possibility of using a sequence of single- and half-cycle attosecond pulses to generate and ultrafast control light-induced population difference gratings has been demonstrated. However, such studies have been carried out using different approximations, such as the sudden perturbation theory and the two-level model for the resonant medium. In this paper, based on the numerical solution of constitutive equations for elements of the density matrix and wave equation it is shown that it is possible to generate and control population gratings in a three-level medium without using the approximation of sudden perturbations used in previous studies. It is shown that taking into account the additional level of the medium does not lead to a violation of the effect of generating such gratings. This extends the applicability of previous results.

Dynamic Single-Leg Balance Tests of Physiotherapy Students: A Comparison of Body-Active Weight Shift Test and Two Sudden Disturbance Tests

BACKGROUND: Balance is essential to maintain and stabilize the transition from static to dynamic posture. The human body can maintain the center of gravity within the base of support and to process input from vision, the vestibular apparatus, and the somatic senses. AIM: The research aimed to check the correlation of the active body-weight shift test (Y balance test [YBT]) and two sudden perturbation tests in physiotherapy students. METHODS: In a cross-sectional study, a descriptive research design was used. Twenty-nine healthy adults (14 men and 15 women) with a mean age of 23.6 ± 6.3 were tested using the active body-weight shift test and two sudden perturbation tests. A descriptive statistical analysis using correlation coefficients was performed. RESULTS: Our subjects’ average values of the test results meet the normative values. There is a correlation between the YBT test and the crossover hop test in the anterior (p < 0.01), posterior-medial, and posterior-lateral directions (p < 0.05), and the triple-hop test forward in the posterior-medial and posterior-lateral directions (p < 0.05), and anterior direction (p < 0.01) for the left extremity, except for the anterior direction to the right. With the right extremity, there is a correlation between the YBT test and the crossover hop test and triple-hop test forward in the posterior medial (p < 0.05), the crossover hop test in the posterior medial and posterior lateral to the left (p < 0.05), and the right (p < 0.01), but no correlation in the anterior direction in either of them. CONCLUSION: The data of all physiotherapy students in our study meet the normative data, and no difference due to gender has been observed. There is a correlation between the active body-weight shift test and sudden perturbation tests with or without lateral movement for the left extremity, but not for the right extremity. We can assume better results when standing on an undominant limb, which can lead to insufficient support when standing on a dominant limb. What should not be the case in providing patient safety.

The interaction of in vivo muscle operating lengths and passive stiffness in rat hindlimbs.

The operating length of a muscle is a key determinant of its ability to produce force in vivo. Muscles that operate near the peak of their force-length relationship will generate higher forces whereas muscle operating at relatively short length may be safe from sudden lengthening perturbations and subsequent damage. At longer lengths, passive mechanical properties have the potential to contribute to force or constrain operating length with stiffer muscle-tendon units theoretically being restricted to shorter lengths. Connective tissues typically increase in density during aging, thus increasing passive muscle stiffness and potentially limiting the operating lengths of muscle during locomotion. Here, we compare in vivo and in situ muscle strain from the medial gastrocnemius in young (7 months old) and aged (30-32 months old) rats presumed to have varying passive tissue stiffness to test the hypothesis that stiffer muscles operate at shorter lengths relative to their force-length relationship. We measured in vivo muscle operating length during voluntary locomotion on inclines and flat trackways and characterized the muscle force-length relationship of the medial gastrocnemius using fluoromicrometry. Although no age-related results were evident, rats of both age groups demonstrated a clear relationship between passive stiffness and in vivo operating length, such that shorter operating lengths were significantly correlated with greater passive stiffness. Our results suggest that increased passive stiffness may restrict muscles to operating lengths shorter than optimal lengths, potentially limiting force capacity during locomotion.

Effect of smartphone use on cervical spine stability

Using a smartphone often involves a sustained head-forward tilt posture, which may deteriorate the mechanism of muscle reaction efficiency or reduce the stiffness of connective tissues of the cervical spine. These changes in muscular and connective tissues can impair cervical spine stability and contribute to developing neck pain symptoms. In this experiment, change in the cervical spine stability associated with a sustained smartphone use posture was evaluated by quantifying the effective stiffness and the reflexive responses of the head to sudden perturbations. Seventeen young smartphone users maintained their heads tilted forward approximately 30° for 30 min while watching videos on their smartphones in sitting. Data show that the measures of cervical spine stability did not change significantly after the smartphone use task despite developing mild to moderate neck and upper body discomfort symptoms. Study findings imply that keeping the head tilt posture for 30 min for smartphone use did not significantly alter spinal stability, rejecting its association with neck discomfort.

Quick speech motor correction in the absence of auditory feedback.

A quick correction mechanism of the tongue has been formerly experimentally observed in speech posture stabilization in response to a sudden tongue stretch perturbation. Given its relatively short latency (< 150 ms), the response could be driven by somatosensory feedback alone. The current study assessed this hypothesis by examining whether this response is induced in the absence of auditory feedback. We compared the response under two auditory conditions: with normal versus masked auditory feedback. Eleven participants were tested. They were asked to whisper the vowel /e/ for a few seconds. The tongue was stretched horizontally with step patterns of force (1 N during 1 s) using a robotic device. The articulatory positions were recorded using electromagnetic articulography simultaneously with the produced sound. The tongue perturbation was randomly and unpredictably applied in one-fifth of trials. The two auditory conditions were tested in random order. A quick compensatory response was induced in a similar way to the previous study. We found that the amplitudes of the compensatory responses were not significantly different between the two auditory conditions, either for the tongue displacement or for the produced sounds. These results suggest that the observed quick correction mechanism is primarily based on somatosensory feedback. This correction mechanism could be learned in such a way as to maintain the auditory goal on the sole basis of somatosensory feedback.

Thermal processes in anisotropic metal complexes induced by non-adiabatic switching of magnetic field.

In this article we analyze the thermal processes in magnetically anisotropic metal complexes under the action of non-adiabatic switching of magnetic field. Using the non-stationary perturbation theory for the case of sudden perturbation, we show that this field can cause not only heat release, but also heat absorption, interconnected with the axial zero field splitting (parameter D) in a paramagnetic metal complex. As an illustrative example we consider the simplest S = 1-complexes having "easy axis" and "easy plane" types of anisotropy influenced by the magnetic field that is suddenly turned off. We demonstrate that the character of the thermal processes (heat dissipation or absorption) depends on the sign of D and direction of applied field and so the analysis of these processes can be in principle used as a complementary tool (in addition to SQIUD magnetometry, EPR spectroscopy and INS) for studying magnetic anisotropy. The conditions under which the non-adiabatic switching of the magnetic field gives rise to the heat absorption are revealed. This unusual phenomenon, which can be called "nonadiabatic field switching cooling", may have practical applications.

A novel high-frequency resonance controllable pneumatic actuator and its high-precision motion trajectory tracking control

The strong nonlinearity and uncertainty of the pneumatic cylinder friction is one of the main reasons for the poor control accuracy of the pneumatic cylinder. For this reason, improving the friction characteristics of the pneumatic cylinder should contribute to the improvement of the pneumatic cylinder motion trajectory tracking accuracy. Reducing friction is a common method to improve the friction characteristics of pneumatic cylinders. In this paper, a novel longitudinal resonance friction-reducing pneumatic cylinder based on the principle of inverse piezoelectric effect is developed from the hardware perspective. Meanwhile, a promising adaptive robust controller (ARC) with online parameter identification and nonlinear robust control function is designed for the pneumatic position servo system from the software perspective. Finally, this paper focuses on exploring the possibility of further improving the accuracy by excitation of high-frequency resonance of the developed novel pneumatic actuator on the basis of the accuracy achievable at the software level (control algorithm). Experimental results show that friction reduction by means of high-frequency resonance can significantly improve the motion trajectory tracking accuracy of the pneumatic system. The maximum tracking error is reduced by 17.95% and 27.87% when tracking sinusoidal reference trajectories of 0.5 Hz and 0.25 Hz, respectively. The maximum tracking error is reduced by 15.79% when tracking a smooth square reference trajectory of 0.25 Hz. In addition, the designed controller is effective and robust to parameter variations and sudden perturbations.

Effect of acute temperature stress on energy metabolism, immune performance and gut microbiome of largemouth bass (Micropterus salmoides)

Frequent occurrences of extreme weather events, particularly severe temperature fluctuations, have significantly impaired the growth and health of fish and resulted in detrimental impacts on aquaculture production. Despite recognition of the crucial role that temperature plays in aquaculture, there is currently inadequate research to assess the consequences of extreme temperature fluctuations on fish health. Hence, we set up acute warming (AW) and cooling groups (AC) by increasing or decreasing water temperature by 8 °C and then gradually restoring the initial temperature (22 °C), to investigate the adaptive regulation of energy metabolism, immune function, and gut microbiota in largemouth bass (Micropterus salmoides). The fish antioxidant system responded to assist their environmental adaptation: both groups showed activation of serum superoxide dismutase (SOD) and catalase (CAT) secretion, and a significant increase in serum total antioxidant capacity (T-AOC) (P < 0.05). Distinct metabolic strategies were employed to cope with sudden environmental perturbations: upon experiencing a temperature decrease (AC1), largemouth bass exhibited a significant increase in serum triglyceride (TG) and cholesterol (CHOL) levels (P < 0.05), coupled with a reduction in blood glucose levels (P < 0.05). However, a considerable reduction in serum TG and CHOL levels was observed after acute warming stage (AW1) (P < 0.05). Following the recovery of temperature, both groups demonstrated a tendency towards normal energy metabolism (CON). Compared to the AW group, the immune function of largemouth bass in the AC group was dramatically affected: alkaline phosphatase (AKP), aspartate transaminase (AST), and alanine transaminase (ALT) increased significantly, while lysozyme (LZM) decreased significantly when the temperature dropped sharply (P < 0.05). After the temperature fluctuations, there were apparent changes in the gut morphology and microbiota of largemouth bass. Microbial functional analysis using the KEGG database revealed apparent alterations in microbial biological functions, especially during the cooling fluctuation (AC). The results indicated that dramatic weather changes, particularly extreme cold, may be detrimental to the health and welfare of largemouth bass.

Does footedness affect bilateral plantar flexor responses to sudden stance perturbations under unilateral lower leg muscular fatigue?

BACKGROUND: Analysis of performance asymmetries has indicated that the right and left cerebral hemispheres are specialized for specific functions of motor control. AIM: In the current investigation, we aimed to evaluate the effect of leg dominance on electrical activation of the plantar flexor muscles in responses to unanticipated stance perturbations in a state muscular fatigue of the dominant leg. METHOD: Fatigue was induced through ankle isometric contraction targeting 40% of maximum voluntary contraction. Muscle activation of the triceps surae of the dominant and non-dominant legs were compared in reactive responses to unanticipated load released from the trunk, leading to forward body sway. Muscular responses were analyzed in two states: pre-fatigue and fatigue of the triceps surae muscles of the dominant leg only. RESULTS: Analysis of magnitude of muscular activation for balance recovery following perturbations revealed fatigue-related compensatory activation in the lateral gastrocnemius muscle, as indicated by over-activation of the non-fatigued/non-dominant leg to compensate for the low muscular activation of the dominant/fatigued leg in the unilateral fatigue state. CONCLUSION: Compensatory behavior between the legs was not evident in the medial gastrocnemius and soleus muscles. Lack of effects related to leg dominance indicates that footedness did not affect automatic muscular responses either in the pre-fatigue or fatigue states.

Development of an Elliptical Perturbation System that provides unexpected perturbations during elliptical walking (the EPES system)

Background‘Perturbation-based balance training’ (PBBT) is a training method that was developed to improve balance reactive responses to unexpected balance loss. This training method is more effective in reducing fall rates than traditional balance training methods. Many PBBTs are performed during standing or treadmill walking which targeted specifically step reactive responses, we however, aimed to develop and build a mechatronic system that can provide unexpected perturbation during elliptical walking the Elliptical Perturbation System (the EPES system), with the aim of improving specifically the trunk and upper limbs balance reactive control.MethodsThis paper describes the development, and building of the EPES system, using a stationary Elliptical Exercise device, which allows training of trunk and upper limbs balance reactive responses in older adults.ResultsThe EPES system provides 3-dimensional small, controlled, and unpredictable sudden perturbations during stationary elliptical walking. We developed software that can identify a trainee’s trunk and arms reactive balance responses using a stereo camera. After identifying an effective trunk and arms reactive balance response, the software controls the EPES system motors to return the system to its horizontal baseline position after the perturbation. The system thus provides closed-loop feedback for a person’s counterbalancing trunk and arm responses, helping to implement implicit motor learning for the trainee. The pilot results show that the EPES software can successfully identify balance reactive responses among participants who are exposed to a sudden unexpected perturbation during elliptical walking on the EPES system.ConclusionsEPES trigger reactive balance responses involving counter-rotation action of body segments and simultaneously evoke arms, and trunk reactive response, thus reactive training effects should be expected.

Age-Related Differences in Kinematics, Kinetics, and Muscle Synergy Patterns Following a Sudden Gait Perturbation: Changes in Movement Strategies and Implications for Fall Prevention Rehabilitation

Falls in older adults are leading causes of fatal and non-fatal injuries, negatively impacting quality of life among those in this demographic. Most elderly falls occur due to unrecoverable limb collapse during balance control in the single-limb support (SLS) phase. To understand why older adults are more susceptible to falls than younger adults, we investigated age-related differences in lower limb kinematics, kinetics, and muscle synergy patterns during SLS, as well as their relationship to postural control strategies. Thirteen older and thirteen younger healthy adults were compared during the SLS phase of balance recovery following an unexpected surface drop perturbation. Compared to younger adults, older adults demonstrated (1) greater trunk flexion, (2) increased hip extension torque and reduced hip abduction torque of the perturbed leg, and (3) higher postural sway. Trunk flexion was correlated with a delayed latency to the start of lateral-to-medial displacement of center of mass from the perturbation onset. The group-specific muscle synergy revealed that older adults exhibited prominent activation of the hip extensors, while younger adults showed prominent activation of the hip abductors. These findings provide insights into targeted balance rehabilitation and indicate ways to improve postural stability and reduce falls in older adults.

Comparison of effects of Mulligan taping and Kinesio taping on ankle neuromuscular control in response to a sudden inversion perturbation in individuals with chronic ankle instability

ObjectivesThis study was aimed to compare the effects of Mulligan taping (MT) with Kinesio taping (KT) and the un-taped ankle on neuromuscular control during a sudden inversion perturbation in individuals with chronic ankle instability (CAI). DesignRandomized, single blind cross-over. SettingBiomechanics lab. Participants16 individuals with chronic ankle instability. Main outcome measuresThe outcome measures were the onset time and magnitude of short (SLR) and medium latency response (MLR) for peroneus brevis (PB), peroneus longus (PL), tibialis anterior (TA), and soleus (SOL) muscles and the TA/P and SOL/TA antagonist co-activation. ResultsIn the groups of KT and MT, the onset time was significantly decreased at post-taping compared to pre-taping, such that for the onset time of PB MLR, the groups of KT and MT had an earlier onset time than the un-taped group. For the magnitude of TA SLR and PB MLR, groups exhibited different behaviors. In the KT group, the magnitude was significantly increased post-taping, however, in the MT group, it was decreased. Regarding the TA/P and SOL/TA co-activation, the groups of KT and MT showed significant changes post-taping. ConclusionThis study suggests that KT and MT significantly affect neuromuscular control in response to a sudden perturbation in individuals with CAI, although the behavior of KT and MT appears to be somewhat different from each other.

Stepping strategies of young adults undergoing sudden external perturbation from different directions

Stepping strategies following external perturbations from different directions is investigated in this work. We analysed the effect of the perturbation angle as well as the level of awareness of individuals and characterised steps out of the sagittal plane between Loaded Side Steps (LSS), Unloaded Medial Steps (UMS) and Unloaded Crossover Steps (UCS). A novel experimental paradigm involving perturbations in different directions was performed on a group of 21 young adults (10 females, 11 males, 20–38 years). Participants underwent 30 randomised perturbations along 5 different angles with different levels of awareness of the upcoming perturbations (with and without wearing a sensory impairment device) for a total of 1260 recorded trials. Results showed that logistic models based on the minimal values of the Margin of Stability (MoS) or on the minimal values of the Time to boundary (Ttb) performed the best in the sagittal plane. However, their accuracy stayed above 79% regardless of the perturbation angle or level of awareness. Regarding the effect of the experimental condition, evidences of different balance recovery behaviours due to the variation of perturbation angles were exposed, but no significant effect of the level of awareness was observed. Finally, we proposed the Distance to Foot boundary (DtFb) as a relevant quantity to characterise the stepping strategies in response to perturbations out of the sagittal plane.

Perturbation-based balance training leads to improved reactive postural responses in individuals with Parkinson's disease and freezing of gait.

Perturbation-based balance training (PBT) exposes individuals to a series of sudden upright balance perturbations to improve their reactive postural responses. In this study, we aimed to evaluate the effect of a short PBT program on body balance recovery following a perturbation in individuals with freezing of gait due to Parkinson's disease. Volunteers (mean age = 64 years, SD = 10.6) were pseudorandomly assigned either to a PBT (n = 9) or to a resistance training (RT, n = 10) group. PBT was implemented through balance perturbations varying in the kind, direction, side, and magnitude of support base displacements. Both groups exercised with progressive difficulty/load activities twice a week for four weeks. Specific gains and generalization to dual-tasking and faster-than-trained support base displacements were evaluated 24 h after the end of the training, and retention was evaluated after 30 days of no training. Results showed that, compared to RT, PBT led to more stable postural responses in the 30-day retention evaluation, as indicated by decreased CoP displacement, velocity, and time to direction reversal and reduced numbers of near-falls. We found no transfer either to a dual-task or to a higher perturbation velocity. In conclusion, a training program based on diverse unpredictable balance perturbations improved the stability of reactive postural responses to those perturbations suffered during the training, without generalization to more challenging tasks.

Cortical oscillations and interareal synchronization as a preparatory activity for postural response.

Neural mechanisms of human standing are expected to be elucidated for preventing fallings. Postural response evoked by sudden external perturbation originates from various areas in the central nervous system. Recent studies have revealed that the corticospinal pathway is one of key nodes for an appropriate postural response. The corticospinal pathway that mediates the early part of electromyographic response is modulated with prediction before a perturbation occurs. Temporal prediction explicitly exhibiting an onset timing contributes to enhancing corticospinal excitability. However, how the cortical activities in the sensorimotor area with temporal prediction are processed before the corticospinal pathway enhancement remains unclear. In this study, using electroencephalography, we investigated how temporal prediction affects both neural oscillations and synchronization between sensorimotor and distal areas. Our results revealed that desynchronization of cortical oscillation at α- and β-bands was observed in the sensorimotor and parietooccipital areas (Cz, CPz, Pz, and POz), and those are nested in the phase at θ-band frequency. Furthermore, a reduction in the interareal phase synchrony in the α-band was induced after the timing cue for the perturbation onset. The phase synchrony at the low-frequency can relay the temporal prediction among the distant areas and initiate the modulation of the local cortical activities. Such modulations contribute to the preparation for sensory processing and motor execution that are necessary for optimal responses.

Age-related differences in reactive balance control and fall-risk in people with chronic stroke

BackgroundImpaired reactive responses to sudden environmental perturbations contribute to heightened fall-risk in healthy aging and neurologically impaired populations. Previous studies have demonstrated individual contributions of paretic and non-paretic sides to fall-risk in people with stroke with variable levels of motor impairment. However, the combined effect of aging and unilateral cortical lesion on reactive balance control is not clearly understood. We therefore aimed to examine age-related differences in reactive balance control and fall-risk during laboratory-induced gait-slips in people with comparable stroke-related motor impairments. MethodsThirteen younger (45.61 ± 4.61 years) and thirteen older (71.92 ± 6.50 years) adults with similar stroke-related impairment (on Fugl-Meyer Lower Extremity Assessment) were exposed to one overground gait-slip under each limb (paretic and non-paretic). Center of mass state stability and slipping kinematics (slip displacement and velocity) were computed. Clinical balance and mobility were also assessed. ResultsOn non-paretic slips, older adults with chronic stroke demonstrated greater falls and lower center of mass stability (its position and velocity) at post-slip touchdown compared to younger adults with chronic stroke (p < 0.01). This was accompanied with a greater peak slip displacement and faster peak slip velocity (p < 0.01). However, there were no such group differences noted on the paretic slips (p > 0.01). ConclusionAging may have an independent, detrimental effect on reactive balance control in people with chronic stroke. Non-paretic deficits in controlling slip intensities (slip displacement and velocity) can accentuate fall-risk in older adults with chronic stroke. Further investigation is necessary to identify additional factors attributing to heightened fall-risk in older adults with chronic stroke.

A 3-DoF robotic platform for the rehabilitation and assessment of reaction time and balance skills of MS patients.

The central nervous system (CNS) exploits anticipatory (APAs) and compensatory (CPAs) postural adjustments to maintain the balance. The postural adjustments comprising stability of the center of mass (CoM) and the pressure distribution of the body influence each other if there is a lack of performance in either of them. Any predictable or sudden perturbation may pave the way for the divergence of CoM from equilibrium and inhomogeneous pressure distribution of the body. Such a situation is often observed in the daily lives of Multiple Sclerosis (MS) patients due to their poor APAs and CPAs and induces their falls. The way of minimizing the risk of falls in neurological patients is by utilizing perturbation-based rehabilitation, as it is efficient in the recovery of the balance disorder. In light of the findings, we present the design, implementation, and experimental evaluation of a novel 3 DoF parallel manipulator to treat the balance disorder of MS. The robotic platform allows angular motion of the ankle based on its anthropomorphic freedom. Moreover, the end-effector endowed with upper and lower platforms is designed to evaluate both the pressure distribution of each foot and the CoM of the body, respectively. Data gathered from the platforms are utilized to both evaluate the performance of the patients and used in high-level control of the robotic platform to regulate the difficulty level of tasks. In this study, kinematic and dynamic analyses of the robot are derived and validated in the simulation environment. Low-level control of the first prototype is also successfully implemented through the PID controller. The capacity of each platform is evaluated with a set of experiments considering the assessment of pressure distribution and CoM of the foot-like objects on the end-effector. The experimental results indicate that such a system well-address the need for balance skill training and assessment through the APAs and CPAs.

Splashes in isotropic media.

The response of a weakly absorbing isotropic medium to a sudden localized perturbation (a "splash") is explained within the framework of linear response theory. In this theory splashes result from the interference of the collective excitations of the medium, with the outcome determined by the interplay between their phase and group velocities as well as the sign of the latter. The salient features of splashes are controlled by the existence of extremal values of the phase and the group velocities: the group velocity gives the expansion rate of the locus of the points where new wave fronts nucleate or existing ones disappear, while the phase velocity determines the large-time expansion rate of a group of wave fronts. If the group velocity is negative in a spectral range and takes on a minimal value within it, then converging wave fronts will be present in the splash. These results are relevant to the studies of several experimentally viable setups, such as a splash on the surface of deep water due to a small pebble or a raindrop, a splash in the two-dimensional electron gas caused by a short voltage pulse applied with the tip of a scanning tunneling microscope, or a bulk splash in superfluid ^{4}He due to formation of an electron bubble. Specifically, the gross features of a splash in superfluid ^{4}He are determined by five extremal velocities. Additionally, due to the existence of a negative group-velocity spectral range, some of the wave fronts in the superfluid splash are converging.

The brain integrates proprioceptive information to ensure robust locomotion.

Robust locomotion relies on information from proprioceptors: sensory organs that communicate the position of body parts to the spinal cord and brain. Proprioceptive circuits in the spinal cord are known to coarsely regulate locomotion in the presence of perturbations. Yet, the regulatory importance of the brain in maintaining robust locomotion remains less clear. Here, through mouse genetic studies and in vivo electrophysiology, we examined the role of the brain in integrating proprioceptive information during perturbed locomotion. The systemic removal of proprioceptors left the mice in a constantly perturbed state, similar to that observed during mechanically perturbed locomotion in wild-type mice and characterised by longer and less accurate synergistic activation patterns. By contrast, after surgically interrupting the ascending proprioceptive projection to the brain through the dorsal column of the spinal cord, wild-type mice showed normal walking behaviour, yet lost the ability to respond to external perturbations. Our findings provide direct evidence of a pivotal role for ascending proprioceptive information in achieving robust, safe locomotion. KEY POINTS: Whether brain integration of proprioceptive feedback is crucial for coping with perturbed locomotion is not clear. We showed a crucial role of the brain for responding to external perturbations and ensure robust locomotion. We used mouse genetics to remove proprioceptors and a spinal lesion model to interrupt the flow of proprioceptive information to the brain through the dorsal column in wild-type animals. Using a custom-built treadmill, we administered sudden and random mechanical perturbations to mice during walking. External perturbations affected locomotion in wild-type mice similar to the absence of proprioceptors in genetically modified mice. Proprioceptive feedback from muscle spindles and Golgi tendon organs contributed to locomotor robustness. Wild-type mice lost the ability to respond to external perturbations after interruption of the ascending proprioceptive projection to the brainstem.