The Moving Platform Aftereffect: Limited Generalization of a Locomotor Adaptation

2004 ◽  
Vol 91 (1) ◽  
pp. 92-100 ◽  
Author(s):  
R. F. Reynolds ◽  
A. M. Bronstein
Keyword(s):  
Baseline Period ◽  
Adaptation Period ◽  
Locomotor Adaptation ◽  
Walking Pattern ◽  
After Effect ◽  
Walking Velocity ◽  
Full Knowledge ◽  
Flashing Light ◽  
Moving Platform ◽  
Insight Into

We have recently described a postural after-effect of walking onto a stationary platform previously experienced as moving, which occurs despite full knowledge that the platform will no longer move. This experiment involves an initial baseline period when the platform is kept stationary (BEFORE condition), followed by a brief adaptation period when subjects learn to walk onto the platform moving at 1.2 m/s (MOVING condition). Subjects are clearly warned that the platform will no longer move and asked to walk onto it again (AFTER condition). Despite the warning, they walk toward the platform with a velocity greater than that observed during the BEFORE condition, and a large forward sway of the trunk is observed once they have landed on the platform. This aftereffect, which disappears within three trials, represents dissociation of knowledge and action. In the current set of experiments, to gain further insight into this phenomenon, we have manipulated three variables, the context, location, and method of the walking task, between the MOVING and AFTER conditions, to determine how far the adaptation will generalize. It was found that when the gait initiation cue was changed from beeps to a flashing light, or vice versa, there was no difference in the magnitude of the aftereffect, either in terms of walking velocity or forward sway of the trunk. Changing the leg with which gait was initiated, however, reduced sway magnitude by approximately 50%. When subjects changed from forward walking to backward walking, the aftereffect was abolished. Similarly, walking in a location other than the mobile platform did not produce any aftereffect. However, in these latter two experiments, the aftereffect reappeared when subjects reverted to the walking pattern used during the MOVING condition. Hence, these results show that a change in abstract context had no influence, whereas any deviation from the way and location in which the moving platform task was originally performed profoundly reduced the size of the aftereffect. Although the moving platform aftereffect is an example of inappropriate generalization by the motor system across time, these results show that this generalization is highly limited to the method and location in which the original adaptation took place.

scholarly journals Different Error Size During Locomotor Adaptation Affects Transfer to Overground Walking Poststroke

2018 ◽  
Vol 32 (12) ◽  
pp. 1020-1030 ◽  
Author(s):  
Carolina C. Alcântara ◽  
Charalambos C. Charalambous ◽  
Susanne M. Morton ◽  
Thiago L. Russo ◽  
Darcy S. Reisman
Keyword(s):  
Catch Trial ◽  
Step Length ◽  
Similar Amount ◽  
Adaptation Period ◽  
Overground Walking ◽  
Locomotor Adaptation ◽  
Walking Pattern ◽  
Gradual Group ◽  
Adaptation Response ◽  
Group A

Background. Studies in neurologically intact subjects suggest that the gradual presentation of small perturbations (errors) during learning results in better transfer of a newly learned walking pattern to overground walking. Whether the same result would be true after stroke is not known. Objective. To determine whether introducing gradual perturbations, during locomotor learning using a split-belt treadmill influences learning the novel walking pattern or transfer to overground walking poststroke. Methods. Twenty-six chronic stroke survivors participated and completed the following walking testing paradigm: baseline overground walking; baseline treadmill walking; split-belt treadmill/adaptation period (belts moving at different speeds); catch trial (belts at same speed); post overground walking. Subjects were randomly assigned to the Gradual group (gradual changes in treadmill belts speed during adaptation) or the Abrupt group (a single, large, abrupt change during adaptation). Step length asymmetry adaptation response on the treadmill and transfer of learning to overground walking was assessed. Results. Step length asymmetry during the catch trial was the same between groups ( P = .195) confirming that both groups learned a similar amount. The magnitude of transfer to overground walking was greater in the Gradual than in the Abrupt group ( P = .041). Conclusions. The introduction of gradual perturbations (small errors), compared with abrupt (larger errors), during a locomotor adaptation task seems to improve transfer of the newly learned walking pattern to overground walking poststroke. However, given the limited magnitude of transfer, future studies should examine other factors that could impact locomotor learning and transfer poststroke.

Gender Differences in Empathy During Adolescence: Does Emotional Self-Awareness Matter?

2021 ◽  
pp. 003329412097663
Author(s):  
Cristina Trentini ◽  
Renata Tambelli ◽  
Silvia Maiorani ◽  
Marco Lauriola
Keyword(s):  
Gender Differences ◽  
Reactivity Index ◽  
Self Awareness ◽  
Emotional States ◽  
Personal Distress ◽  
Full Knowledge ◽  
Emotional Concern ◽  
Insight Into ◽  
Tas 20

Empathy refers to the capacity to experience emotions similar to those observed or imagined in another person, with the full knowledge that the other person is the source of these emotions. Awareness of one's own emotional states is a prerequisite for self-other differentiation to develop. This study investigated gender differences in empathy during adolescence and tested whether emotional self-awareness explained these differences. Two-hundred-eleven adolescents (108 girls and 103 boys) between 14 and 19 years completed the Interpersonal Reactivity Index (IRI) and the Toronto Alexithymia Scale (TAS-20) to assess empathy and emotional self-awareness, respectively. Overall, girls obtained higher scores than boys on IRI subscales like emotional concern, personal distress, and fantasy. Regarding emotional self-awareness, we found gender differences in TAS-20 scores, with girls reporting greater difficulty identifying feelings and less externally oriented thinking than boys. Difficulty identifying feelings explained the greatest personal distress experienced by girls. Lower externally oriented thinking accounted for girls’ greater emotional concern and fantasy. These findings offer an insight into the role of emotional self-awareness–which is essential for self-other differentiation–as an account for gender differences in empathic abilities during adolescence. In girls, difficulty identifying feelings can impair the ability to differentiate between ones’ and others’ emotions, leading them to experience self-focused and aversive responses when confronted with others’ suffering. Conversely, in boys, externally oriented thinking can mitigate personal distress when faced with others’ discomfort.

scholarly journals Limited Attention Diminishes Spatial Suppression From Large Field Glass Patterns

Perception ◽  
2019 ◽  
Vol 48 (4) ◽  
pp. 286-315 ◽  
Author(s):  
Andrea Pavan ◽  
Adriano Contillo ◽  
Filippo Ghin ◽  
Matthew J. Foxwell ◽  
George Mather
Keyword(s):  
Large Scale ◽  
Spatial Summation ◽  
Visual Presentation ◽  
Large Field ◽  
Limited Attention ◽  
Adaptation Period ◽  
After Effect ◽  
Glass Patterns ◽  
Coherence Level

Glass patterns (GPs) consist of randomly distributed dot pairs (dipoles) whose orientations are determined by specific geometric transforms. We investigated the role of visuospatial attention in the processing of global form from GPs by measuring the effect of distraction on adaptation to GPs. In the nondistracted condition, observers were adapted to coherent GPs. After the adaptation period, they were presented with a test GP divided in two halves along the vertical and were required to judge which side of the test GP was more coherent. In the attention-distracted condition, a high-load rapid serial visual presentation task was performed during the adapting period. The magnitude of the form after-effect was measured using a technique that measures the coherence level at which the test GP appears random. The rationale was that if attention has a modulatory effect on the spatial summation of dipoles, in the attention-distracted condition, we should expect a weaker form after-effect. However, the results showed stronger form after-effect in the attention-distracted condition than in the nondistracted condition, suggesting that distraction during adaptation increases the strength of form adaptation. Additional experiments suggested that distraction may reduce the spatial suppression from large-scale textures, strengthening the spatial summation of local-oriented signals.

scholarly journals Blocking trial-by-trial error correction does not interfere with motor learning in human walking

2016 ◽  
Vol 115 (5) ◽  
pp. 2341-2348 ◽  
Author(s):  
Andrew W. Long ◽  
Ryan T. Roemmich ◽  
Amy J. Bastian
Keyword(s):  
Error Correction ◽  
Motor Pattern ◽  
Step Length ◽  
The Other ◽  
Human Walking ◽  
Not Given ◽  
Foot Placement ◽  
Locomotor Adaptation ◽  
Walking Pattern ◽  
Environmental Demands

Movements can be learned implicitly in response to new environmental demands or explicitly through instruction and strategy. The former is often studied in an environment that perturbs movement so that people learn to correct the errors and store a new motor pattern. Here, we demonstrate in human walking that implicit learning of foot placement occurs even when an explicit strategy is used to block changes in foot placement during the learning process. We studied people learning a new walking pattern on a split-belt treadmill with and without an explicit strategy through instruction on where to step. When there is no instruction, subjects implicitly learn to place one foot in front of the other to minimize step-length asymmetry during split-belt walking, and the learned pattern is maintained when the belts are returned to the same speed, i.e., postlearning. When instruction is provided, we block expression of the new foot-placement pattern that would otherwise naturally develop from adaptation. Despite this appearance of no learning in foot placement, subjects show similar postlearning effects as those who were not given any instruction. Thus locomotor adaptation is not dependent on a change in action during learning but instead can be driven entirely by an unexpressed internal recalibration of the desired movement.

scholarly journals A novel optic flow pattern speeds split-belt locomotor adaptation

2014 ◽  
Vol 111 (5) ◽  
pp. 969-976 ◽  
Author(s):  
James M. Finley ◽  
Matthew A. Statton ◽  
Amy J. Bastian
Keyword(s):  
Flow Pattern ◽  
Optic Flow ◽  
Learning Rate ◽  
Locomotor Training ◽  
Belt Speed ◽  
Locomotor Adaptation ◽  
Walking Pattern ◽  
Foot Strike ◽  
Pattern Speeds ◽  
Congruent Group

Visual input provides vital information for helping us modify our walking pattern. For example, artificial optic flow can drive changes in step length during locomotion and may also be useful for augmenting locomotor training for individuals with gait asymmetries. Here we asked whether optic flow could modify the acquisition of a symmetric walking pattern during split-belt treadmill adaptation. Participants walked on a split-belt treadmill while watching a virtual scene that produced artificial optic flow. For the Stance Congruent group, the scene moved at the slow belt speed at foot strike on the slow belt and then moved at the fast belt speed at foot strike on the fast belt. This approximates what participants would see if they moved over ground with the same walking pattern. For the Stance Incongruent group, the scene moved fast during slow stance and vice versa. In this case, flow speed does not match what the foot is experiencing, but predicts the belt speed for the next foot strike. Results showed that the Stance Incongruent group learned more quickly than the Stance Congruent group even though each group learned the same amount during adaptation. The increase in learning rate was primarily driven by changes in spatial control of each limb, rather than temporal control. Interestingly, when this alternating optic flow pattern was presented alone, no adaptation occurred. Our results demonstrate that an unnatural pattern of optic flow, one that predicts the belt speed on the next foot strike, can be used to enhance learning rate during split-belt locomotor adaptation.

Predictive control of ankle stiffness at heel contact is a key element of locomotor adaptation during split-belt treadmill walking in humans

2014 ◽  
Vol 111 (4) ◽  
pp. 722-732 ◽  
Author(s):  
Tetsuya Ogawa ◽  
Noritaka Kawashima ◽  
Toru Ogata ◽  
Kimitaka Nakazawa
Keyword(s):  
Muscle Activity ◽  
Stance Phase ◽  
Treadmill Walking ◽  
Adaptation Period ◽  
Propulsive Force ◽  
Locomotor Adaptation ◽  
Ankle Stiffness ◽  
Heel Contact ◽  
Braking Force ◽  
The Impact

Split-belt treadmill walking has been extensively utilized as a useful model to reveal the adaptability of human bipedal locomotion. While previous studies have clearly identified different types of locomotor adaptation, such as reactive and predictive adjustments, details of how the gait pattern would be adjusted are not fully understood. To gain further knowledge of the strategies underlying split-belt treadmill adaptation, we examined the three-dimensional ground reaction forces (GRF) and lower limb muscle activities during and after split-belt treadmill walking in 22 healthy subjects. The results demonstrated that the anterior component of the GRF (braking force) showed a clear pattern of adaptation and subsequent aftereffects. The muscle activity in the tibialis anterior muscle during the early stance phase was associated with the change of braking force. In contrast, the posterior component of GRF (propulsive force) showed a consistent increase/decrease in the fast/slow leg during the adaptation period and was not followed by subsequent aftereffects. The muscle activity in the gastrocnemius muscle during the stance phase gradually decreased during the adaptation phase and then showed a compensatory reaction during the washout phase. The results indicate that predictive feedforward control is required to set the optimal ankle stiffness in preparation for the impact at the heel contact and passive feedback control is used for the production of reflexively induced propulsive force at the end of the stance phase during split-belt treadmill adaptation. The present study provides information about the detailed mechanisms underlying split-belt adaptation and should be useful for the construction of specific rehabilitation protocols.

scholarly journals Split-belt walking adaptation recalibrates sensorimotor estimates of leg speed but not position or force

2015 ◽  
Vol 114 (6) ◽  
pp. 3255-3267 ◽  
Author(s):  
Alejandro Vazquez ◽  
Matthew A. Statton ◽  
Stefanie A. Busgang ◽  
Amy J. Bastian
Keyword(s):  
Motor Learning ◽  
Contact Force ◽  
Learning Task ◽  
Lower Limbs ◽  
Locomotor Adaptation ◽  
Walking Pattern ◽  
Speed Perception ◽  
Perceptual Changes ◽  
Walking Adaptation ◽  
Leg Position

Motor learning during reaching not only recalibrates movement but can also lead to small but consistent changes in the sense of arm position. Studies have suggested that this sensory effect may be the result of recalibration of a forward model that associates motor commands with their sensory consequences. Here we investigated whether similar perceptual changes occur in the lower limbs after learning a new walking pattern on a split-belt treadmill—a task that critically involves proprioception. Specifically, we studied how this motor learning task affects perception of leg speed during walking, perception of leg position during standing or walking, and perception of contact force during stepping. Our results show that split-belt adaptation leads to robust motor aftereffects and alters the perception of leg speed during walking. This is specific to the direction of walking that was trained during adaptation (i.e., backward or forward). The change in leg speed perception accounts for roughly half of the observed motor aftereffect. In contrast, split-belt adaptation does not alter the perception of leg position during standing or walking and does not change the perception of stepping force. Our results demonstrate that there is a recalibration of a sensory percept specific to the domain of the perturbation that was applied during walking (i.e., speed but not position or force). Furthermore, the motor and sensory consequences of locomotor adaptation may be linked, suggesting overlapping mechanisms driving changes in the motor and sensory domains.

Self-initiated gait increases susceptibility to the moving platform after-effect

Neuroreport ◽  
2006 ◽  
Vol 17 (14) ◽  
pp. 1503-1505 ◽  
Author(s):  
Raymond F. Reynolds ◽  
Adolfo M. Bronstein
Keyword(s):  
After Effect ◽  
Moving Platform
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