Spatially selective enhancement of proprioceptive acuity following motor learning.

Department of Psychology, The University of Western Ontario, 1151 Richmond St., London, ON Canada.
Journal of Neurophysiology (Impact Factor: 3.3). 03/2011; 105(5):2512-21. DOI: 10.1152/jn.00949.2010
Source: PubMed

ABSTRACT It is well recognized that the brain uses sensory information to accurately produce motor commands. Indeed, most research into the relationship between sensory and motor systems has focused on how sensory information modulates motor function. In contrast, recent studies have begun to investigate the reverse: how sensory and perceptual systems are tuned based on motor function, and specifically motor learning. In the present study we investigated changes to human proprioceptive acuity following recent motor learning. Sensitivity to small displacements of the hand was measured before and after 10 min of motor learning, during which subjects grasped the handle of a robotic arm and guided a cursor to a series of visual targets randomly located within a small workspace region. We used a novel method of assessing proprioceptive acuity that avoids active movement, interhemispheric transfer, and intermodality coordinate transformations. We found that proprioceptive acuity improved following motor learning, but only in the region of the arm's workspace explored during learning. No proprioceptive improvement was observed when motor learning was performed in a different location or when subjects passively experienced limb trajectories matched to those of subjects who actively performed motor learning. Our findings support the idea that sensory changes occur in parallel with changes to motor commands during motor learning.

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    ABSTRACT: Motor learning is reflected in changes to the brain's functional organization as a result of experience. We show here that these changes are not limited to motor areas of the brain and indeed that motor learning also changes sensory systems. We test for plasticity in sensory systems using somatosensory evoked potentials (SEPs). A robotic device is used to elicit somatosensory inputs by displacing the arm in the direction of applied force during learning. We observe that following learning there are short latency changes to the response in somatosensory areas of the brain that are reliably correlated with the magnitude of motor learning: Subjects that learn more show greater changes in SEP magnitude. The effects we observe are tied to motor learning. When the limb is displaced passively such that subjects experience similar movements but without experiencing learning, no changes in the evoked response are observed. Sensorimotor adaptation thus alters the neural coding of somatosensory stimuli.
    Journal of Neurophysiology 01/2013; · 3.30 Impact Factor
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    ABSTRACT: A complex interplay has been demonstrated between motor and sensory systems. We have recently shown that motor learning leads to changes in the sensed position of the limb (Ostry et al. 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.
    Journal of Neurophysiology 11/2012; · 3.30 Impact Factor
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    ABSTRACT: STUDY DESIGN: Controlled laboratory study: cross-sectional. OBJECTIVE: To determine if proprioception, measured by the threshold to detection of passive movement (TDPM), differed in individuals who regularly participate in moderate intensity exercise for fitness as compared to individuals involved in high intensity skilled exercise. BACKGROUND: Previous research has been equivocal as to whether exercise training is associated with superior proprioceptive acuity, in particular, exercise that includes dynamic postural challenges such as cutting/pivoting. METHODS: Two groups of 25 healthy individuals (18 to 32 years old) were recruited. One group consisted of individuals who performed moderate activity level exercises for 5 to 10 hours per week. Participants in the other group performed high activity level exercises, including high speed cutting and pivoting activities, at least 10 hours per week. Proprioception was determined using TDPM, in which the knee was slowly extended or flexed at an angular velocity of 0.5°/second or less from a starting position of 40° of knee flexion. An average of TDPM measures of both limbs was determined. RESULTS: Individuals participating in competitive high intensity skilled exercise demonstrated better acuity (average of both limbs) of TDPM, (mean ± SD, 0.81±0.38°; P<.001) than those participating in moderate intensity exercise for fitness (1.53 ± 0.58°). A low but statistically significant association (r = -0.38; P=.006) was found between weekly duration of exercise and proprioceptive threshold as measured by TDPM. CONCLUSION: These results suggest that perceptual thresholds of passive movement may be enhanced dependent on activity level and associated postural challenge, and that higher level and increased amount of exercise may promote enhanced neurosensory processing in these individuals. Consequently, high intensity skilled training may deserve further emphasis in orthopedic rehabilitation. J Orthop Sports Phys Ther, Epub 18 March 2013. doi:10.2519/jospt.2013.4403.
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