scholarly journals Cerebellar motor learning: are environment dynamics more important than error size?

2013 ◽  
Vol 110 (2) ◽  
pp. 322-333 ◽  
Author(s):  
Tricia L. Gibo ◽  
Sarah E. Criscimagna-Hemminger ◽  
Allison M. Okamura ◽  
Amy J. Bastian
Keyword(s):  
Motor Learning ◽  
Force Field ◽  
Complex Dynamics ◽  
External Perturbation ◽  
Joint Space ◽  
Relative Effect ◽  
Small Error ◽  
Cerebellar Damage ◽  
Movement Dynamics ◽  
Compensatory Strategy

Cerebellar damage impairs the control of complex dynamics during reaching movements. It also impairs learning of predictable dynamic perturbations through an error-based process. Prior work suggests that there are distinct neural mechanisms involved in error-based learning that depend on the size of error experienced. This is based, in part, on the observation that people with cerebellar degeneration may have an intact ability to learn from small errors. Here we studied the relative effect of specific dynamic perturbations and error size on motor learning of a reaching movement in patients with cerebellar damage. We also studied generalization of learning within different coordinate systems (hand vs. joint space). Contrary to our expectation, we found that error size did not alter cerebellar patients' ability to learn the force field. Instead, the direction of the force field affected patients' ability to learn, regardless of whether the force perturbations were introduced gradually (small error) or abruptly (large error). Patients performed best in fields that helped them compensate for movement dynamics associated with reaching. However, they showed much more limited generalization patterns than control subjects, indicating that patients rely on a different learning mechanism. We suggest that patients typically use a compensatory strategy to counteract movement dynamics. They may learn to relax this compensatory strategy when the external perturbation is favorable to counteracting their movement dynamics, and improve reaching performance. Altogether, these findings show that dynamics affect learning in cerebellar patients more than error size.

scholarly journals Motor learning in reaching tasks leads to homogenization of task space error distribution

2021 ◽  
Author(s):  
Puneet Singh ◽  
Oishee Ghosal ◽  
Aditya Murthy ◽  
Ashitava Ghodal
Keyword(s):  
Motor Learning ◽  
Force Field ◽  
Error Distribution ◽  
Task Space ◽  
Field Perturbation ◽  
Directional Dependence ◽  
Reaching Tasks ◽  
Space Error ◽  
Human Arm ◽  
Point To Point

A human arm, up to the wrist, is often modelled as a redundant 7 degree-of-freedom serial robot. Despite its inherent nonlinearity, we can perform point-to-point reaching tasks reasonably fast and with reasonable accuracy in the presence of external disturbances and noise. In this work, we take a closer look at the task space error during point-to-point reaching tasks and learning during an external force-field perturbation. From experiments and quantitative data, we confirm a directional dependence of the peak task space error with certain directions showing larger errors than others at the start of a force-field perturbation, and the larger errors are reduced with repeated trials implying learning. The analysis of the experimental data further shows that a) the distribution of the peak error is made more uniform across directions with trials and the error magnitude and distribution approaches the value when no perturbation is applied, b) the redundancy present in the human arm is used more in the direction of the larger error, and c) homogenization of the error distribution is not seen when the reaching task is performed with the non-dominant hand. The results support the hypothesis that not only magnitude of task space error, but the directional dependence is reduced during motor learning and the workspace is homogenized possibly to increase the control efficiency and accuracy in point-to-point reaching tasks. The results also imply that redundancy in the arm is used to homogenize the workspace, and additionally since the bio-mechanically similar dominant and non-dominant arms show different behaviours, the homogenizing is actively done in the central nervous system.

scholarly journals Plastic Changes in Hand Proprioception Following Force-Field Motor Learning

2010 ◽  
Vol 104 (3) ◽  
pp. 1213-1215 ◽  
Author(s):  
Daniel J. Goble ◽  
Joaquin A. Anguera
Keyword(s):  
Motor Learning ◽  
Force Field ◽  
Recent Work ◽  
Recent Article ◽  
Sensory Feedback ◽  
Motor Output ◽  
Feedback Processing ◽  
Plastic Changes ◽  
Proprioceptive Function ◽  
New Evidence

Motor neurophysiologists are placing greater emphasis on sensory feedback processing than ever before. In line with this shift, a recent article by Ostry and colleagues provided timely new evidence that force-field motor learning influences not only motor output, but also proprioceptive sense. In this Neuro Forum, the merits and limitations of Ostry and colleagues are explored in the context of recent work on proprioceptive function, including several recent studies from this journal.

Multiple Motor Learning Experiences Enhance Motor Adaptability

2004 ◽  
Vol 16 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Rachael D. Seidler
Keyword(s):  
Motor Learning ◽  
Learning Experiences ◽  
External Perturbation ◽  
Skill Learning ◽  
Learning Ability ◽  
Learning Capacity ◽  
Control Subjects ◽  
Movement Sequence ◽  
Experimental Subjects ◽  
Gain Change

Traditional motor learning theory emphasizes that skill learning is specific to the context and task performed. Recent data suggest, however, that subjects exposed to a variety of motor learning paradigms may be able to acquire general, transferable knowledge about skill learning processes. I tested this idea by having subjects learn five different motor tasks, three that were similar to each other and two that were not related. A group of experimental subjects first performed a joystick-aiming task requiring adaptation to three different visuomotor rotations, with a return to the null conditions between each exposure. They then performed the same joystick-aiming task but had to adapt to a change in display gain instead of rotation. Lastly, the subjects used the joystickaiming task to learn a repeating sequence of movements. Two groups of control subjects performed the same number of trials, but learned only the gain change or the movement sequence. Experimental subjects showed generalization of learning across the three visuomotor rotations. Experimental subjects also exhibited transfer of learning ability to the gain change and the movement sequence, resulting in faster learning than that seen in the control subjects. However, transient perturbations affected the movements of the experimental subjects to a greater extent than those of the control subjects. These data demonstrate that humans can acquire a general enhancement in motor skill learning capacity through experience, but it comes with a cost. Although movement becomes more adaptable following multiple learning experiences, it also becomes less stable to external perturbation.

scholarly journals Motor learning and its sensory effects: time course of perceptual change and its presence with gradual introduction of load

2013 ◽  
Vol 109 (3) ◽  
pp. 782-791 ◽  
Author(s):  
Andrew A. G. Mattar ◽  
Mohammad Darainy ◽  
David J. Ostry
Keyword(s):  
Motor Learning ◽  
Force Field ◽  
Motor Performance ◽  
Time Course ◽  
Sensory Perception ◽  
Learning Task ◽  
Perceptual Change ◽  
Sensory Effects ◽  
Gradual Introduction ◽  
Lateral Displacements

A complex interplay has been demonstrated between motor and sensory systems. We showed recently that motor learning leads to changes in the sensed position of the limb (Ostry DJ, Darainy M, Mattar AA, Wong J, Gribble PL. J Neurosci 30: 5384–5393, 2010). Here, we document further the links between motor learning and changes in somatosensory perception. To study motor learning, we used a force field paradigm in which subjects learn to compensate for forces applied to the hand by a robotic device. We used a task in which subjects judge lateral displacements of the hand to study somatosensory perception. In a first experiment, we divided the motor learning task into incremental phases and tracked sensory perception throughout. We found that changes in perception occurred at a slower rate than changes in motor performance. A second experiment tested whether awareness of the motor learning process is necessary for perceptual change. In this experiment, subjects were exposed to a force field that grew gradually in strength. We found that the shift in sensory perception occurred even when awareness of motor learning was reduced. These experiments argue for a link between motor learning and changes in somatosensory perception, and they are consistent with the idea that motor learning drives sensory change.

IMPAIRED NON-MOTOR LEARNING AND ERROR DETECTION ASSOCIATED WITH CEREBELLAR DAMAGE

Brain ◽  
1992 ◽  
Vol 115 (1) ◽  
pp. 155-178 ◽  
Author(s):  
JULIE A. FIEZ ◽  
STEVEN E. PETERSEN ◽  
MARSHALL K. CHENEY ◽  
MARCUS E. RAICHLE
Keyword(s):  
Motor Learning ◽  
Error Detection ◽  
Cerebellar Damage

scholarly journals On the encoding capacity of human motor adaptation

2021 ◽  
Author(s):  
Seung-Yeon Kim ◽  
Jae-Woon Kwon ◽  
Jin-Min Kim ◽  
Frank Chong-Woo Park ◽  
Sang-Hoon Yeo
Keyword(s):  
Motor Learning ◽  
Force Field ◽  
Information Content ◽  
Motor Adaptation ◽  
Movement Speed ◽  
Limiting Factor ◽  
Information Encoding ◽  
Motor Primitives ◽  
Human Motor ◽  
Human Motor Adaptation

Primitive-based models of motor learning suggest that adaptation occurs by tuning the responses of motor primitives. Based on this idea, we consider motor learning as an information encoding procedure, that is, a procedure of encoding a motor skill into primitives. The capacity of encoding is determined by the number of recruited primitives, which depends on how many primitives are "visited" by the movement, and this leads to a rather counter-intuitive prediction that faster movement, where a larger number of motor primitives are involved, allows learning more complicated motor skills. Here we provide a set of experimental results that support this hypothesis. First, we show that learning occurs only with movement, i.e., only with non-zero encoding capacity. When participants were asked to counteract a rotating force applied to a robotic handle, they were unable to do so when maintaining a static posture but were able to adapt when making small circular movements. Our second experiment further investigated how adaptation is affected by movement speed. When adapting to a simple (low-information-content) force field, fast (high-capacity) movement did not have an advantage over slow (low-capacity) movement. However, for a complex (high-information-content) force field, the fast movement showed a significant advantage over slow movement. Our final experiment confirmed that the observed benefit of high-speed movement is only weakly affected by mechanical factors. Taken together, our results suggest that the encoding capacity is a genuine limiting factor of human motor adaptation.

scholarly journals Pupil-linked arousal modulates trial-by-trial motor adaptation in humans

2021 ◽  
Author(s):  
Atsushi Yokoi ◽  
Jeff Weiler
Keyword(s):  
Motor Learning ◽  
Force Field ◽  
Learning Rate ◽  
Sudden Increase ◽  
Rapid Reduction ◽  
Non Invasive ◽  
Arousal System ◽  
Series Of Experiments ◽  
The Rich ◽  
Task Irrelevant

Research in reward-based decision-making showed that humans and animals dynamically modulate learning rate according to their belief about environmental change (volatility) and surprise about observation. Recent evidence also suggests that neuromodulator noradrenaline (NA) signals volatility and surprise. Despite the rich anatomical evidence suggesting the potential influence of NA on the motor system, it is still elusive how NA and volatility/surprise affect human motor learning. To address this issue, we ran a series of experiments in which we simultaneously tracked the pupil diameter, a non-invasive proxy for the central NA/arousal activity, during a short-term force-field reach adaptation paradigm. A sudden increase in error due to the force-field resulted in increased pupil dilation during movement followed by an elevated baseline diameter in the following trials. These online and offline pupil responses showed a consistent pattern with surprise and volatility simulated by a recent computational model which dynamically adjusts learning rate according to volatility estimated from experienced error (surprise). However, unlike the model's prediction, when participants experienced frequent reversals in force-field, the size of pupil responses rapidly diminished regardless of large errors induced by reversals. We further confirmed that the causal manipulation of participants' arousal by task-irrelevant auditory stimuli modulated the single-trial motor learning rate. Collectively, these results provide a compelling evidence that NA/arousal system acts as a common modulator of learning rate in both cognitive and motor domains. Rapid reduction in pupil responses at reversals suggests that error sensitivity for computing current environmental uncertainty and surprise is also highly dynamic.

scholarly journals Separate representations of dynamics in rhythmic and discrete movements: evidence from motor learning

2011 ◽  
Vol 105 (4) ◽  
pp. 1722-1731 ◽  
Author(s):  
Ian S. Howard ◽  
James N. Ingram ◽  
Daniel M. Wolpert
Keyword(s):  
Motor Learning ◽  
Force Field ◽  
Motor System ◽  
Neural Mechanisms ◽  
Control Mechanisms ◽  
Discrete Movements ◽  
Field Perturbation ◽  
Movement Path ◽  
Neural Representations ◽  
Separate Control

Rhythmic and discrete arm movements occur ubiquitously in everyday life, and there is a debate as to whether these two classes of movements arise from the same or different underlying neural mechanisms. Here we examine interference in a motor-learning paradigm to test whether rhythmic and discrete movements employ at least partially separate neural representations. Subjects were required to make circular movements of their right hand while they were exposed to a velocity-dependent force field that perturbed the circularity of the movement path. The direction of the force-field perturbation reversed at the end of each block of 20 revolutions. When subjects made only rhythmic or only discrete circular movements, interference was observed when switching between the two opposing force fields. However, when subjects alternated between blocks of rhythmic and discrete movements, such that each was uniquely associated with one of the perturbation directions, interference was significantly reduced. Only in this case did subjects learn to corepresent the two opposing perturbations, suggesting that different neural resources were employed for the two movement types. Our results provide further evidence that rhythmic and discrete movements employ at least partially separate control mechanisms in the motor system.

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