Article

Seeing Is Believing: Effects of Visual Contextual Cues on Learning and Transfer of Locomotor Adaptation

Johns Hopkins University, Baltimore, Maryland, United States
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 12/2010; 30(50):17015-22. DOI: 10.1523/JNEUROSCI.4205-10.2010
Source: PubMed

ABSTRACT

Devices such as robots or treadmills are often used to drive motor learning because they can create novel physical environments. However, the learning (i.e., adaptation) acquired on these devices only partially generalizes to natural movements. What determines the specificity of motor learning, and can this be reliably made more general? Here we investigated the effect of visual cues on the specificity of split-belt walking adaptation. We systematically removed vision to eliminate the visual-proprioceptive mismatch that is a salient cue specific to treadmills: vision indicates that we are not moving while leg proprioception indicates that we are. We evaluated the adaptation of temporal and spatial features of gait (i.e., timing and location of foot landing), their transfer to walking over ground, and washout of adaptation when subjects returned to the treadmill. Removing vision during both training (i.e., on the treadmill) and testing (i.e., over ground) strongly improved the transfer of treadmill adaptation to natural walking. Removing vision only during training increased transfer of temporal adaptation, whereas removing vision only during testing increased the transfer of spatial adaptation. This dissociation reveals differences in adaptive mechanisms for temporal and spatial features of walking. Finally training without vision increased the amount that was learned and was linked to the variability in the behavior during adaptation. In conclusion, contextual cues can be manipulated to modulate the magnitude, transfer, and washout of device-induced learning in humans. These results bring us closer to our ultimate goal of developing rehabilitation strategies that improve movements beyond the clinical setting.

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Available from: Gelsy Torres-Oviedo, May 20, 2015
    • "By maintaining the original learning context but increasing sensorimotor variability, we expected that changes in control needed to match previously learned task performance would strengthen skill. This is consistent with improved retention and generalization following small rather than abrupt errors during single-session learning [17, 41]. Our results might have shown a different pattern had the intervention been devised to amplify error. "
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    ABSTRACT: Newly acquired motor skills become stabilized through consolidation [1]. However, we know from daily life that consolidated skills are modified over multiple bouts of practice and in response to newfound challenges [2]. Recent evidence has shown that memories can be modified through reconsolidation, in which previously consolidated memories can re-enter a temporary state of instability through retrieval, and in order to persist, undergo re-stabilization [3-8]. Although observed in other memory domains [5, 6], it is unknown whether reconsolidation leads to strengthened motor skills over multiple episodes of practice. Using a novel intervention after the retrieval of a consolidated skill, we found that skill can be modified and enhanced through exposure to increased sensorimotor variability. This improvement was greatest in those participants who could rapidly adjust their sensorimotor output in response to the relatively large fluctuations presented during the intervention. Importantly, strengthening required the reactivation of the consolidated skill and time for changes to reconsolidate. These results provide a key demonstration that consolidated motor skills continue to change as needed through the remapping of motor command to action goal, with strong implications for rehabilitation.
    No preview · Article · Jan 2016 · Current biology: CB
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    • "Subjects also exploit 90 redundancy between the local variables stride length and stride time to maintain constant speed during 91 steady-state treadmill walking (Dingwell et al. 2010). Locomotor adaptation research has typically 92 focused on the changes occurring in limb-level or interlimb parameters like stride length, stride time and 93 ground reaction force (Finley et al. 2013; Dingwell et al. 2010; Torres-Oviedo and Bastian 2010; 94 Vasudevan and Bastian 2010; Dingwell et al. 1996). These global changes have a direct bearing on 95 locomotor performance and must often be modified according to the experimental paradigm. "
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    ABSTRACT: During movement, errors are typically corrected only if they hinder performance. Preferential correction of task-relevant deviations is described by the minimal intervention principle, but has not been demonstrated in the joints during locomotor adaptation. We studied hopping as a tractable model of locomotor adaptation of the joints within the context of a limb-force-specific task space. Subjects hopped while adapting to shifted visual feedback that induced them to increase peak ground reaction force (GRF). We hypothesized subjects would preferentially reduce task-relevant joint torque deviations over task-irrelevant deviations to increase peak GRF. We employed a modified uncontrolled manifold analysis to quantify task-relevant and task-irrelevant joint torque deviations for each individual hop cycle. As would be expected by the explicit goal of the task, peak GRF errors decreased in early adaptation before reaching steady state during late adaptation. Interestingly, during the early adaptation performance improvement phase, subjects reduced GRF errors by decreasing only the task-relevant joint torque deviations. In contrast, during the late adaption performance maintenance phase, all torque deviations decreased in unison regardless of task relevance. In de-adaptation, when the shift in visual feedback was removed, all torque deviations decreased in unison, possibly because performance improvement was too rapid to detect changes in only the task-relevant dimension. We conclude that limb force adaptation in hopping switches from a minimal intervention strategy during performance improvement to a noise reduction strategy during performance maintenance, which may represent a general control strategy for locomotor adaptation of limb force in other bouncing gaits, such as running. Copyright © 2014, Journal of Neurophysiology.
    Full-text · Article · Dec 2014 · Journal of Neurophysiology
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    • "Therefore, it needs to be investigated, if improvements of our FB training on the treadmill can be transferred to over ground walking. Even though it has been shown that removing vision during treadmill adaptation could improve overground transfer of the new walking pattern (Torres-Oviedo and Bastian, 2010), the ultimate goal would be to train in everyday life situations. For this purpose, mobile gait analysis systems are promising tools that provide the possibility for measurement of joint angles and time-distance parameters. "
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    ABSTRACT: Background: Incomplete spinal cord injury (iSCI) leads to motor and sensory deficits. Even in ambulatory persons with good motor function an impaired proprioception may result in an insecure gait. Limited internal afferent feedback (FB) can be compensated by provision of external FB by therapists or technical systems. Progress in computational power of motion analysis systems allows for implementation of instrumented real-time FB. The aim of this study was to test if individuals with iSCI can normalize their gait kinematics during FB and more importantly maintain an improvement after therapy. Methods: Individuals with chronic iSCI had to complete 6 days (1 day per week) of treadmill-based FB training with a 2 weeks pause after 3 days of training. Each day consists of an initial gait analysis followed by 2 blocks with FB/no-FB. During FB the deviation of the mean knee angle during swing from a speed matched reference (norm distance, ND) is visualized as a number. The task consists of lowering the ND, which was updated after every stride. Prior to the tests in patients the in-house developed FB implementation was tested in healthy subjects with an artificial movement task. Results: Four of five study participants benefited from FB in the short and medium term. Decrease of mean ND was highest during the first 3 sessions (from 3.93 ± 1.54 to 2.18 ± 1.04). After the pause mean ND stayed in the same range than before. In the last 3 sessions the mean ND decreased slower (2.40 ± 1.18 to 2.20 ± 0.90). Direct influences of FB ranged from 60 to 15% of reduction in mean ND compared to initial gait analysis and from 20 to 1% compared to no-FB sessions. Conclusions: Instrumented kinematic real-time FB may serve as an effective adjunct to established gait therapies in normalizing the gait pattern after incomplete spinal cord injury. Further studies with larger patient groups need to prove long term learning and the successful transfer of newly acquired skills to activities of daily living.
    Full-text · Article · Jun 2014 · Frontiers in Human Neuroscience
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