Biology subjects

Torres-Oviedo, G.

Publications and source records attributed to Torres-Oviedo, G..

17 recordsLinked to original sources

bioRxiv2026

Perceptual sensitivity supports online control, while perceptual errors drive motor memory formation during locomotor adaptation

1.To maintain stable locomotion, the nervous system must continually adapt, whether reacting to an unexpected perturbation, such as a trip on uneven terrain, or anticipating external demands, such as walking on snow, by forming and updating motor memories. Error-based learning is the dominant computational account of such adaptation, in which motor commands are updated to reduce prediction errors, that is, the mismatch between predicted and actual limb state. Yet this framework was largely defined in reduced, single-effector paradigms, where the sensory consequences of movement are isolated and the prediction error is directly observable. Whether the same principle governs whole-body, multi-segmental, multi-sensory behaviors such as walking has remained untested, owing in part to the challenge of identifying a behavioral proxy for prediction errors in this complex, dynamic setting. Here, we combined a split-belt treadmill paradigm with a novel method for quantifying perception of leg motion to address this open question. We found two perceptual contributions to locomotor adaptation: perceptual sensitivity predicted initial motor corrections during early adaptation, whereas perceptual errors (i.e., the mismatch between perceived and observed leg speed) predicted the magnitude of motor aftereffects during post-adaptation. Together, these findings demonstrate that locomotor adaptation is fundamentally constrained by perception of limb motion. Our results identify perceived limb motion as a behavioral proxy for prediction errors, establishing error-based learning, long characterized in reduced tasks, as a core computational principle underlying human locomotion. 2. SignificanceError-based learning is the dominant account of how the brain adapts movement, yet it was defined almost entirely in reduced laboratory tasks, such as cursor rotations, planar reaching, and saccades, where prediction errors are directly observable. Whether it governs whole-body behaviors such as walking has remained untested. Using a novel measure of leg-motion perception during split-belt walking, we show that two dimensions of perception contribute separably to adaptation. Perceptual sensitivity, a proxy for sensory uncertainty, relates to real-time motor corrections, consistent with Bayesian integration. Perceptual error, a proxy for the prediction error that underlies error-based learning, relates to motor memory formation. These findings establish leg-motion perception as a behavioral window onto the computations driving locomotor adaptation, providing a framework for understanding individual and clinical variability in motor behavior.

bioengineering↗

bioRxiv2026

Locomotor savings relies on attentional control of walking in older, but not younger adults

The ability to recall learned movements and rapidly adapt to environmental changes, known as locomotor savings, is crucial for mobility in community-dwelling older adults. However, the influence of aging on locomotor savings and the underlying mechanisms remains poorly understood. Attentional compensation is a particularly relevant mechanism because the control of automatic motor behaviors like walking tend to recruit more attentional/executive resources with aging. We hypothesize that locomotor savings is diminished with age and relies on attentional rather than automatic control of walking. To test this, we compared savings of a novel walking pattern learned on a split-belt treadmill, where each leg moves at a different speed, across multiple days in 21 older and 21 younger adults. Attentional control of walking was assessed by overground dual-task walking while prefrontal cortex (PFC) activity was recorded using functional near-infrared spectroscopy (fNIRS). We found that older adults exhibited less locomotor savings than younger adults after practice. Older adults also relied more on attentional resources during dual-task walking. Importantly, greater locomotor savings was associated with higher attentional control of walking in older adults, suggesting that the use of attentional resources during challenging walking facilitates the recall of previously learned movements. These results indicate that cognitive compensation strategies utilizing attentional resources are important neural mechanisms modulating locomotor savings. Understanding the role of cognitive compensation in locomotor savings may inform rehabilitation design to enhance mobility in older adults ensuring movement corrections practiced in clinical settings are saved for long-term benefit in daily life.

neuroscience↗

bioRxiv2025

Webers Law in walking: sensory scaling is observed in multi-sensory, dynamic tasks

We frequently adjust our behaviors in response to environmental changes. This behavioral flexibility requires adequate sensitivity to external stimuli to maintain optimal motor performance under evolving task demands. There is abundant empirical evidence that sensitivity scaling follows Webers Law. Webers Law states that the perception of a sensory stimulus is scaled by the magnitude of the background sensory context. However, Webers Law has so far been assessed only in uni-sensory static tasks, and it remains an open question whether this principle extends to multi-sensory, dynamic motor tasks. To address this question, we assessed somatosensory perception of relative leg motion (i.e., speed differences between right and left legs) in healthy young adults. We hypothesized that sensitivity to differences in leg speed would follow Webers Law. We estimated participants sensitivity to speed differences (sensory stimuli) using two-alternative forced choice (2AFC) tasks. Participants walked at a testing speed representing distinct sensory contexts: slow speed (low-intensity sensory context), comfortable speed (medium-intensity sensory context), and fast speed (high-intensity sensory context). All groups compared their assigned testing speed against a common reference speed. We found that sensitivity to speed differences followed Webers Law at both slow and fast non-habitual walking speeds, but this scaling differed when walking near the comfortable walking speed. Moreover, Webers Law scaling was reproduced by a drift-diffusion model that used only reaction times to quantify sensitivity, indicating that the evidence accumulation process described by the model can account for Webers Law scaling in multi-sensory, dynamic motor tasks, as well as in static, uni-sensory tasks. Author summaryAdapting motor behaviors to environmental changes requires precise sensory perception to maintain optimal performance. Webers Law, a fundamental principle of psychophysics, describes how sensory perception is scaled relative to background stimulus intensity to prevent sensory overload; however, its applicability to multi-sensory dynamic motor behaviors like locomotion remains unclear. Our results show that Webers Law partially explains how we perceive leg movement differences during walking. We found that sensitivity to speed differences scales following Webers Law when walking at non-habitual slow or fast speeds. However, near comfortable walking, people are actually more sensitive than at other speeds, departing from Webers Law. A drift-diffusion model replicated Webers Law scaling during walking, showing that the same mechanistic framework can explain the scaling of sensation in both static, uni-sensory tasks and dynamic, multi-sensory activities like walking.

bioengineering↗

bioRxiv2023

Novel automaticity index characterizing dual task walking reveals a cognitive ability-related decline in gait automaticity.

Gait automaticity refers to the ability to walk with minimal recruitment of attentional networks typically mediated through the prefrontal cortex (PFC). Reduced gait automaticity is common with aging, contributing to an increased risk of falls and reduced quality of life. A common assessment of gait automaticity involves examining PFC activation using near-infrared spectroscopy (fNIRS) during dual-task (DT) paradigms, such as walking while performing a cognitive task. However, neither PFC activity nor task performance in isolation measures automaticity accurately. For example, greater PFC activation could be interpreted as worse gait automaticity when accompanied by poorer DT performance, but when accompanied by better DT performance, it could be seen as successful compensation. Thus, there is a need to incorporate behavioral performance and PFC measurements for a more comprehensive evaluation of gait automaticity. To address this need, we propose a novel automaticity index as an analytical approach that combines changes in PFC activity with changes in DT performance to quantify gait automaticity. We validated the index in 173 participants ([≥]65 y/o) who completed DTs with two levels of difficulty while PFC activation was recorded with fNIRS. The two DTs consisted of reciting every other letter of the alphabet while walking over either an even or uneven surface. We found that as DT difficulty increases, more participants showed the anticipated decrease in automaticity as measured by the novel index compared to PFC activation. Furthermore, when comparing across individuals, lower cognitive function related to worse automaticity index, but not PFC activation or DT performance. In sum, the proposed index better quantified the differences in automaticity between tasks and individuals by providing a unified measure of gait automaticity that includes both brain activation and performance. This new approach opens exciting possibilities to assess participant-specific deficits and compare rehabilitation outcomes from gait automaticity interventions.

neuroscience↗

bioRxiv2023

Multi-site identification and generalization of clusters of walking impairment in individuals with chronic stroke

BackgroundWalking patterns in stroke survivors are highly heterogeneous, which poses a challenge in systematizing treatment prescriptions for walking rehabilitation interventions. ObjectiveWe used bilateral spatiotemporal and force data during walking to create a multi-site research sample to: 1) identify clusters of walking behaviors in people post-stroke and neurotypical controls, and 2) determine the generalizability of these walking clusters across different research sites. We hypothesized that participants post-stroke will have different walking impairments resulting in different clusters of walking behaviors, which are also different from control participants. MethodsWe gathered data from 81 post-stroke participants across four research sites and collected data from 31 control participants. Using sparse K-means clustering, we identified walking clusters based on 17 spatiotemporal and force variables. We analyzed the biomechanical features within each cluster to characterize cluster-specific walking behaviors. We also assessed the generalizability of the clusters using a leave-one-out approach. ResultsWe identified four stroke clusters: a fast and asymmetric cluster, a moderate speed and asymmetric cluster, a slow cluster with frontal plane force asymmetries, and a slow and symmetric cluster. We also identified a moderate speed and symmetric gait cluster composed of controls and participants post-stroke. The moderate speed and asymmetric stroke cluster did not generalize across sites. ConclusionsAlthough post-stroke walking patterns are heterogenous, these patterns can be systematically classified into distinct clusters based on spatiotemporal and force data. Future interventions could target the key features that characterize each cluster to increase the efficacy of interventions to improve mobility in people post-stroke.

neuroscience↗

bioRxiv2022

Large errors increase the generalization of locomotor adaptation depending on the error direction.

Generalization in motor adaptation involves the transfer of movements beyond the adaptation context. We investigated the effect of size (large vs. small) and direction (unidirectional vs. bidirectional) of performance errors during adaptation on the generalization of walking patterns from a split-belt treadmill (training context) to overground (testing context). We hypothesized that unusual errors (i.e., large unidirectional or bidirectional errors) would serve as contextual cues limiting generalization. The size of unidirectional errors was modulated either implicitly (i.e., gradual vs. semi-abrupt split-belt perturbations) or explicitly (i.e., through instructed visual feedback). Bidirectional errors were induced by a sudden removal of the split-perturbation after a long adaptation period, resulting in errors in the opposite direction to those at the start of the adaptation period. Our findings did not support our hypothesis. We found that bidirectional, but not large, performance errors limited generalization across contexts, which could be mediated by two distinct mechanisms. On the one hand, bidirectional errors upon removal of the split-perturbation are also experienced when transitioning to overground walking. Thus, bidirectional errors may facilitate switching between distinct walking patterns, thereby limiting generalization. On the other hand, large unidirectional errors induce more motor adaptation, which might lead to more generalization.

neuroscience↗

bioRxiv2021

Older adults generalize their movements across walking contexts more than young during gradual and abrupt split-belt walking

Generalization of movements from experienced to novel situations is a critical aspect of motor learning. It has been demonstrated that the training period when a movement is learned influences the movements generalization to untrained situations. However, little is known about how healthy aging affects these processes. For example, young adults exhibit greater generalization of movements learned on a device (e.g. split-belt treadmill or robotic arm) to movements without it (e.g, overground walking or unconstrained reaching) when participants experience small vs. large perturbations on the training device. Here, we investigated whether a similar effect would be observed in older adults. To this end, we compared the generalization of split-belt adaptation to overground walking in older (75.9{+/-}4.8 years old) and young adults (24.7{+/-}5.9 years old) when adapted gradually (i.e., small perturbations) vs. abruptly (i.e., large perturbations). We found that both age groups adapted more to the abrupt condition compared to the gradual condition, which resulted in greater adaptation effects (i.e., aftereffects) on the treadmill in the abrupt than the gradual groups. We also found that older adults generalize more than young adults, regardless of the perturbation schedule (i.e., gradual or abrupt). Our results suggest that abrupt perturbations during adaptation do not limit the generalization of movement in older adults-perhaps because they are more likely to attribute them to their own faulty movements. These results suggest that large perturbations are better than small when training older clinical populations since abrupt disturbances would lead to more adaptation and generalization of corrected movements in older people.

bioengineering↗

bioRxiv2020

High-human acuity of speed asymmetry during walking

1Despite its central role in the proper functioning of the motor system, sensation has been less studied than motor output in sensorimotor adaptation paradigms. This deficit is probably due to the difficulty of measuring sensation: while motor output has easily observable consequences, sensation is by definition an internal variable of the motor system. In this study we asked how well can subjects estimate relevant environmental changes inducing motor adaptation. We addressed this question in the context of walking on a split-belt treadmill, which allows subjects to experience distinct belt speeds for each leg. We used a two-alternative forced-choice perceptual task (2AFC) in which subjects report which belt they thought to be moving slower. We characterized baseline accuracy in this task for healthy human subjects, and found 75% accuracy for 75 mm/s speed differences. Additionally, we used a drift-diffusion model of the task that could account for both accuracy and reaction times. We conclude that 2AFC tasks can be used to probe subjects estimates of the environment and that this approach opens an avenue for investigating perceptual deficits and its relation to motor impairments in clinical populations.

bioengineering↗

bioRxiv2020

Cognitive and motor perseveration are associated in older adults

Aging causes perseveration (difficulty to switch between actions) in motor and cognitive tasks, suggesting that the same neural processes could govern these abilities in older adults. To test this, we evaluated the relation between independently measured motor and cognitive perseveration in young (21.4{+/-}3.7 y/o) and older participants (76.5{+/-}2.9 y/o). Motor perseveration was measured with a locomotor task in which participants had to transition between distinct walking patterns. Cognitive perseveration was measured with a card matching task in which participants had to switch between distinct matching rules. We found that perseveration in the cognitive and motor domains were positively related in older, but not younger individuals, such that participants exhibiting greater perseveration in the motor task also perseverated more in the cognitive task. Additionally, exposure reduces motor perseveration: older adults who had practiced the motor task could transition between walking patterns as proficiently as naive, young individuals. Our results suggest an overlap in neural processes governing cognitive and motor perseveration with aging and that exposure can counteract the age-related motor perseveration. HighlightsO_LIMovement carryover from the treadmill to overground indicates motor perseveration. C_LIO_LIGreater motor and cognitive perseveration are associated in older adults. C_LIO_LIMotor perseveration in older adults can be reduced with practice. C_LIO_LINew motor memories are similarly forgotten in older and younger adults. C_LI

bioengineering↗

bioRxiv2019

Motorized shoes induce robust sensorimotor adaptation in walking

The motor system has the flexibility to update motor plans according to systematic changes in the environment or the body. This capacity is studied in the laboratory through sensorimotor adaptation paradigms imposing sustained and predictable motor demands specific to the task at hand. However, these studies are tied to the laboratory setting. Thus, we asked if a portable device could be used to elicit locomotor adaptation outside the laboratory. To this end we tested the extent to which a pair of motorized shoes could induce similar locomotor adaptation to split-belt walking, which is a well-established sensorimotor adaptation paradigm in locomotion. We specifically compared two groups of young, healthy subjects adapted on the treadmill by moving their feet at different speeds with a split-belt treadmill or with a pair of motorized shoes. We found that the adaptation of joint motions and measures of spatial and temporal asymmetry, which are commonly used to quantify sensorimotor adaptation in locomotion, were indistinguishable between groups. We only found small differences in the join angle kinematics during baseline walking between the groups-potentially due to the relatively large weight and height of the motorized shoes. Our results indicate that robust sensorimotor adaptation in walking can be induced with a paired of motorized shoes, opening the exciting possibility to study sensorimotor adaptation during more realistic situations outside the laboratory.

bioengineering↗

bioRxiv2019

Augmenting propulsion demands during split-belt walking increases locomotor adaptation in the asymmetric motor system

BackgroundPromising studies have shown that the mobility of individuals with hemiparesis due to brain lesions, such as stroke, can improve through motor adaptation protocols forcing patients to use their affected limb more. However, little is known about how to facilitate this process. Here we asked if increasing propulsion demands during split-belt walking (i.e., legs moving at different speeds) leads to more motor adaptation and more symmetric gait in survivors of a stroke, as we previously observed in subjects without neurological disorders.\n\nMethodsWe investigated the effect of propulsion forces on locomotor adaptation during and after split-belt walking in the asymmetric motor system post-stroke. To test this, 12 subjects in the chronic phase post-stroke experienced a split-belt protocol in a flat and incline session so as to contrast the effects of two different propulsion demands. Step length asymmetry and propulsion forces were used to compare the motor behavior between the two sessions because these are clinically relevant measures that are altered by split-belt walking.\n\nResultsThe incline session resulted in more symmetric step lengths during late split-belt walking and larger after-effects following split-belt walking. In both testing sessions, subjects who have had a stroke adapted to regain speed and slope-specific leg orientations similarly to young, intact adults. Importantly, leg orientations during baseline walking were predictive of those achieved during split-belt walking, which in turn predicted each individuals post-adaptation behavior.\n\nConclusionThese results indicated that survivors of a stroke can adapt their movements to meet leg-specific kinetic demands. This promising finding suggests that augmenting propulsion demands during split-belt walking could favor symmetric walking in individuals who had a stroke, possibly making split-belt interventions a more effective gait rehabilitation strategy.

bioengineering↗

bioRxiv2019

Cerebral contribution to the execution, but not recalibration, of motor commands in a novel walking environment.

Human movements are flexible as they continuously adapt to changes in the environment by updating planned actions and generating corrective movements. Planned actions are updated upon repeated exposure to predictable changes in the environment, whereas corrective responses serve to overcome unexpected environmental transitions. It has been shown that corrective muscle responses are tuned through sensorimotor adaptation induced by persistent exposure to a novel situation. Here, we asked whether cerebral structures contribute to this recalibration using stroke as a disease model. To this end, we characterized changes in muscle activity in stroke survivors and unimpaired individuals before, during, and after walking on a split-belt treadmill moving the legs at different speeds, which has been shown to induce recalibration of corrective responses in walking in healthy individuals. We found that the recalibration of corrective muscle activity was comparable between stroke survivors and controls, which was surprising given then known deficits in feedback responses post-stroke. Also, the intact recalibration in the group of stroke survivors contrasted the patients limited ability to adjust their muscle activity during steady state split-belt walking compared to controls. Our results suggest that the recalibration and execution of motor commands in new environments are partially dissociable: cerebral lesions interfere with the execution, but not the recalibration, of motor commands upon novel movement demands.

neuroscience↗

bioRxiv2019

Explicit control of step timing during split-beltwalking reveals interdependent recalibrationof movements in space and time

Split-belt treadmills that move the legs at different speeds are thought to update internal representations of the environment, such that this novel condition generates a new locomotor pattern with distinct spatio-temporal features compared to those of regular walking. It is unclear the degree to which such recalibration of movements in the spatial and temporal domains is interdependent. In this study, we explicitly altered subjects limb motion in either space or time during split-belt walking to determine its impact on the adaptation of the other domain. Interestingly, we observed that motor adaptation in the spatial domain was susceptible to altering the temporal domain, whereas motor adaptation in the temporal domain was resilient to modifying the spatial domain. This nonreciprocal relation suggests a hierarchical organization such that the control of timing in locomotion has an effect on the control of limb position. This is of translational interest because clinical populations often have a greater deficit in one domain compared to the other. Our results suggest that explicit changes to temporal deficits cannot occur without modifying the spatial control of the limb.

neuroscience↗

bioRxiv2019

Split-Belt walking induces changes in active, but not passive, perception of step length

The estimation of limbs position is critical for motor control. While motor adaptation changes the estimation of limb position in volitional arm movements, this has not been observed in locomotion. We hypothesized that split-belt walking with the legs moving at different speeds changes the estimation of the legs position when taking a step. Thus, we assessed young subjects perception of step length (i.e., inter-feet distance at foot landing) when they moved their legs (active perception) or these were moved by the experimenter (passive perception). Step lengths active, but not passive perception was altered by split-belt walking; indicating that adapted efferent inputs changed the perceived limbs position without changing information from sensory signals. These perceptual shifts were sensitive to how they were tested: they were observed in the trailing, but not the leading leg, and they were more salient when tested with short than long step lengths. Our results suggest that sensory changes following motor adaptation might arise from mismatched limb position estimates from different sensory sources (i.e., proprioception and vision), which is less prominent in walking. We also speculate that split-belt walking could improve the deficient perception of step length post-stroke, which contributes to their gait asymmetry impairing patients mobility.

neuroscience↗

bioRxiv2018

Augmenting cognitive load during split-belt walking increases the generalization of motor memories across walking contexts

Cognitive load plays a role on the movement recalibration induced by sensorimotor adaptation, but little is known about its impact on the generalization of movements from trained to untrained situations. We hypothesized that altering cognitive load by distracting subjects during sensorimotor adaptation would facilitate the generalization of recalibrated movements beyond the training condition. We reasoned that awareness of the novel condition inducing adaptation could be used to consciously contextualize movements to that particular situation. To test this hypothesis, young adults adapted their gait on a split-belt treadmill (moving their legs at different speeds) while they observed visual information that either distracted them or made them aware of the speed difference between their feet. We assessed the adaptation and aftereffects of spatial and temporal gait features known to adapt and generalize differently when walking on the treadmill or overground. We found similar adaptation and aftereffects on the treadmill across all groups. In contrast, both groups with altered cognitive load (i.e., distraction and awareness groups) generalized their movements from the treadmill to overground more than controls, who walked without altered cognitive load. Of note, this effect was only observed in temporal gait features, which are less susceptible to online motor adjustments, and were eliminated upon experiencing large errors by briefly removing the split perturbation during adaptation (i.e., catch trial). Taken together, increasing cognitive demands during sensorimotor adaptation facilitates the generalization of movement recalibration, but this cognitive-mediated effect cannot eliminate the specificity of actions due to context-specific errors.

neuroscience↗

bioRxiv2018

The adaptation of muscle activity during split-belt walking reveals age-dependent decline of motor learning

Recent studies suggest that planned and corrective actions are recalibrated during some forms of motor adaptation. However, corrective (a.k.a., reactive) movements in human locomotion are thought to simply reflect sudden environmental changes independently from sensorimotor recalibration. Thus, we asked if corrective responses can indicate the motor systems adapted state following prolonged exposure to a novel walking situation inducing sensorimotor adaptation. We recorded electromyographic signals bilaterally on 15 leg muscles before, during, and after split-belts walking (i.e., novel walking situation), in which the legs move at different speeds. We exploited the rapid temporal dynamics of corrective responses upon introduction or removal of an unexpected speed transition to isolate them from the overall motor output. We found that corrective muscle activity was structurally different following short vs. long exposures to split-belts walking. Only after a long exposure, removal of the novel environment elicited corrective muscle patterns that matched those expected in response to a perturbation opposite to the one originally experienced. This indicated that individuals who recalibrated their motor system adopted split-belts environment as their new "normal" and transitioning back to the original walking environment causes subjects to react as if it was novel to them. Interestingly, this learning declined with age, but steady state modulation of muscle activity during split-belts walking did not, suggesting potentially different neural mechanisms underlying these motor patterns. Taken together, our results show that corrective motor commands reflect the adapted state of the motor system, which is less flexible as we age. Significance statementWe showed that corrective muscle activity elicited by sudden environmental transitions is revealing of the underlying recalibration process during sensorimotor adaptation. This allowed us to identify age-related decline in motor learning that was not discernible from kinematic measures conventionally used in motor adaptation studies. These findings suggest that older populations may have limited potential to correct their movements through error-based protocols simply given their age. Moreover, we describe the distinct motor patterns recruited during and after the split condition, informing our understanding of the therapeutic effect of this task. Therefore, our detailed EMG characterization provides valuable normative data of muscle activity that could be reinforced with repeated exposure of split-belts walking.

neuroscience↗

bioRxiv2018

Large propulsion demands increase locomotor learning at the expense of step length asymmetry

There is a clinical interest in increasing the extent of locomotor learning induced by split-belt treadmills that move each leg at different speeds. However, factors facilitating locomotor learning are poorly understood. We hypothesized that augmenting the braking forces, rather than propulsion forces, experienced at the feet would increase locomotor adaptation and learning. To test this, forces were modulated during split-belt walking with distinct slopes: inclined (larger propulsion than braking), declined (larger braking than propulsion), and flat (similar propulsion and braking). These groups were compared using step length asymmetry, which is a clinically relevant measure robustly adapted on split-belt treadmills. Unexpectedly, the group with larger propulsion demands (i.e., the incline group) adapted faster and more, and had larger after-effects when the split-belt perturbation was removed. We also found that subjects who propelled more during baseline and experienced larger disruptions of propulsion forces in early adaptation exhibited greater after-effects, which further highlights the catalytic role of propulsion on locomotor learning. The relevance of mechanical demands on shaping our movements was also indicated by the steady state split-belt behavior, during which each group recovered their baseline leg orientation to meet leg-specific force demands at the expense of step length symmetry. Notably, the flat group was nearly symmetric, whereas the incline and decline group overshot and undershot symmetry, respectively. Taken together, our results indicate that forces propelling the body facilitate gait adaptation during split-belt walking. Therefore, interventions that increase propulsion demands may be a viable strategy for augmenting locomotor learning in individuals with hemiparesis.\n\nKey Points SummaryO_LISplit-belt walking (i.e., legs moving at different speeds) can induce locomotor learning and even improve hemiparetic gait, but little is known about how to facilitate this process.\nC_LIO_LIWe investigated the effect of braking and propulsion forces on locomotor learning by testing young unimpaired subjects on the split-belt condition at different slopes (i.e., flat, decline, and incline), which distinctively modified these forces.\nC_LIO_LIPropulsion forces facilitated locomotor learning indicated by 1) greater adaptation and after-effects following split-belt walking of the inclined group, which experienced larger propulsion demands and 2) a positive correlation between individual after-effects and subject-specific propulsion during regular walking and initial steps in the split condition.\nC_LIO_LIInterestingly, incline and decline groups self-selected asymmetric step lengths at steady state in the split condition, challenging the prominent view that step length asymmetry is a biomarker for inefficient gait.\nC_LIO_LIOur results suggest that interventions augmenting propulsion demands could correct hemiparetic gait more effectively.\nC_LI

neuroscience↗