@article {3382, title = {Electrocorticographic activity over sensorimotor cortex and motor function in awake behaving rats.}, journal = {J Neurophysiol}, volume = {113}, year = {2015}, month = {04/2015}, pages = {2232-41}, abstract = {

Sensorimotor cortex exerts both short-term and long-term control over the spinal reflex pathways that serve motor behaviors. Better understanding of this control could offer new possibilities for restoring function after central nervous system trauma or disease. We examined the impact of ongoing sensorimotor cortex (SMC) activity on the largely monosynaptic pathway of the H-reflex, the electrical analog of the spinal stretch reflex. In 41 awake adult rats, we measured soleus electromyographic (EMG) activity, the soleus H-reflex, and electrocorticographic activity over the contralateral SMC while rats were producing steady-state soleus EMG activity. Principal component analysis of electrocorticographic frequency spectra before H-reflex elicitation consistently revealed three frequency bands: μβ (5-30 Hz), low γ (γ1; 40-85 Hz), and high γ (γ2; 100-200 Hz). Ongoing (i.e., background) soleus EMG amplitude correlated negatively with μβ power and positively with γ1 power. In contrast, H-reflex size correlated positively with μβ power and negatively with γ1 power, but only when background soleus EMG amplitude was included in the linear model. These results support the hypothesis that increased SMC activation (indicated by decrease in μβ power and/or increase in γ1 power) simultaneously potentiates the H-reflex by exciting spinal motoneurons and suppresses it by decreasing the efficacy of the afferent input. They may help guide the development of new rehabilitation methods and of brain-computer interfaces that use SMC activity as a substitute for lost or impaired motor outputs.

}, keywords = {brain-computer interface, cortex, H-Reflex, Motor control, Spinal Cord}, issn = {1522-1598}, doi = {10.1152/jn.00677.2014}, url = {http://www.ncbi.nlm.nih.gov/pubmed/25632076}, author = {Chadwick B. Boulay and Xiang Yang Chen and Jonathan Wolpaw} } @article {3383, title = {Persistent beneficial impact of H-reflex conditioning in spinal cord-injured rats.}, journal = {J Neurophysiol}, volume = {112}, year = {2014}, month = {11/2014}, pages = {2374-81}, abstract = {

Operant conditioning of a spinal cord reflex can improve locomotion in rats and humans with incomplete spinal cord injury. This study examined the persistence of its beneficial effects. In rats in which a right lateral column contusion injury had produced asymmetric locomotion, up-conditioning of the right soleus H-reflex eliminated the asymmetry while down-conditioning had no effect. After the 50-day conditioning period ended, the H-reflex was monitored for 100 [{\textpm}9 (SD)] (range 79-108) more days and locomotion was then reevaluated. After conditioning ended in up-conditioned rats, the H-reflex continued to increase, and locomotion continued to improve. In down-conditioned rats, the H-reflex decrease gradually disappeared after conditioning ended, and locomotion at the end of data collection remained as impaired as it had been before and immediately after down-conditioning. The persistence (and further progression) of H-reflex increase but not H-reflex decrease in these spinal cord-injured rats is consistent with the fact that up-conditioning improved their locomotion while down-conditioning did not. That is, even after up-conditioning ended, the up-conditioned H-reflex pathway remained adaptive because it improved locomotion. The persistence and further enhancement of the locomotor improvement indicates that spinal reflex conditioning protocols might supplement current therapies and enhance neurorehabilitation. They may be especially useful when significant spinal cord regeneration becomes possible and precise methods for retraining the regenerated spinal cord are needed.

}, keywords = {H-reflex conditioning, Learning, Locomotion, Memory, Motor control, Rehabilitation, spinal cord injury, spinal cord plasticity}, issn = {1522-1598}, doi = {10.1152/jn.00422.2014}, url = {http://www.ncbi.nlm.nih.gov/pubmed/25143542}, author = {Yi Chen and Lu Chen and Wang, Yu and Jonathan Wolpaw and Xiang Yang Chen} } @article {3110, title = {H-reflex down-conditioning greatly increases the number of identifiable GABAergic interneurons in rat ventral horn.}, journal = {Neuroscience letters}, volume = {452}, year = {2009}, month = {03/2009}, pages = {124{\textendash}129}, abstract = {H-reflex down-conditioning increases GABAergic terminals on spinal cord motoneurons. To explore the origins of these terminals, we studied the numbers and distributions of spinal cord GABAergic interneurons. The number of identifiable GABAergic interneurons in the ventral horn was 78\% greater in rats in which down-conditioning was successful than in naive rats or rats in which down-conditioning failed. No increase occurred in other spinal lamina or on the contralateral side. This finding supports the hypothesis that the corticospinal tract influence that induces the motoneuron plasticity underlying down-conditioning reaches the motoneuron through GABAergic interneurons in the ventral horn.}, keywords = {activity-dependent plasticity, GABAergic interneurons, H-reflex conditioning, learning and memory, Motor control, Spinal Cord}, issn = {0304-3940}, doi = {10.1016/j.neulet.2009.01.054}, url = {http://www.ncbi.nlm.nih.gov/pubmed/19383426}, author = {Wang, Yu and Pillai, Shreejith and Jonathan Wolpaw and Xiang Yang Chen} } @article {3188, title = {Effects of H-reflex up-conditioning on GABAergic terminals on rat soleus motoneurons.}, journal = {The European journal of neuroscience}, volume = {28}, year = {2008}, month = {08/2008}, pages = {668{\textendash}674}, abstract = {To explore the role of spinal cord plasticity in motor learning, we evaluated the effects of H-reflex operant conditioning on GABAergic input to rat spinal motoneurons. Previous work indicated that down-conditioning of soleus H-reflex increases GABAergic input to soleus motoneurons. This study explored the effect of H-reflex up-conditioning on GABAergic input. Of nine rats exposed to H-reflex up-conditioning, up-conditioning was successful (H-reflex increase >or= 20\%) in seven and failed (change < 20\%) in two. These rats and eight naive control (i.e. unconditioned) rats were injected with cholera toxin subunit B-conjugated Alexa fluor 488 into the soleus muscle to retrogradely label soleus motoneurons. Sections containing soleus motoneurons were processed for GAD(67) [one of the two principal forms of the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD)] with an ABC-peroxidase system. Two blinded independent raters counted and measured GABAergic terminals on these motoneurons. Unlike successful down-conditioning, which greatly increased the number of identifiable GABAergic terminals on the motoneurons, up-conditioning did not significantly change GABAergic terminal number. Successful up-conditioning did produce slight but statistically significant increases in GABAergic terminal diameter and soma coverage. These results are consistent with other data indicating that up- and down-conditioning are not mirror images of each other, but rather have different mechanisms. Although the marked changes in GABAergic terminals with down-conditioning probably contribute to H-reflex decrease, the modest changes in GABAergic terminals associated with up-conditioning may be compensatory or reactive plasticity, rather than the plasticity responsible for H-reflex increase. As a variety of spinal and supraspinal GABAergic neurons innervate motoneurons, the changes found with up-conditioning may be in terminals other than those affected in successful down-conditioning.}, keywords = {activity-dependent plasticity, Learning, Memory, Motor control, Spinal Cord}, issn = {1460-9568}, doi = {10.1111/j.1460-9568.2008.06370.x}, url = {http://www.ncbi.nlm.nih.gov/pubmed/18657184}, author = {Pillai, Shreejith and Wang, Yu and Jonathan Wolpaw and Xiang Yang Chen} } @article {3193, title = {Motor learning changes GABAergic terminals on spinal motoneurons in normal rats.}, journal = {The European journal of neuroscience}, volume = {23}, year = {2006}, month = {01/2006}, pages = {141{\textendash}150}, abstract = {The role of spinal cord plasticity in motor learning is largely unknown. This study explored the effects of H-reflex operant conditioning, a simple model of motor learning, on GABAergic input to spinal motoneurons in rats. Soleus motoneurons were labeled by retrograde transport of a fluorescent tracer and GABAergic terminals on them were identified by glutamic acid decarboxylase (GAD)67 immunoreactivity. Three groups were studied: (i) rats in which down-conditioning had reduced the H-reflex (successful HRdown rats); (ii) rats in which down-conditioning had not reduced the H-reflex (unsuccessful HRdown rats) and (iii) unconditioned (naive) rats. The number, size and GAD density of GABAergic terminals, and their coverage of the motoneuron, were significantly greater in successful HRdown rats than in unsuccessful HRdown or naive rats. It is likely that these differences are due to modifications in terminals from spinal interneurons in lamina VI-VII and that the increased terminal number, size, GAD density and coverage in successful HRdown rats reflect and convey a corticospinal tract influence that changes motoneuron firing threshold and thereby decreases the H-reflex. GABAergic terminals in spinal cord change after spinal cord transection. The present results demonstrate that such spinal cord plasticity also occurs in intact rats in the course of motor learning and suggest that this plasticity contributes to skill acquisition.}, keywords = {activity-dependent plasticity, GABA, H-Reflex, Memory, Motor control, Spinal Cord}, issn = {0953-816X}, doi = {10.1111/j.1460-9568.2005.04547.x}, url = {http://www.ncbi.nlm.nih.gov/pubmed/16420424}, author = {Wang, Yu and Pillai, Shreejith and Jonathan Wolpaw and Xiang Yang Chen} } @article {3066, title = {Operant conditioning of H-reflex can correct a locomotor abnormality after spinal cord injury in rats.}, journal = {The Journal of neuroscience : the official journal of the Society for Neuroscience}, volume = {26}, year = {2006}, month = {11/2006}, pages = {12537{\textendash}12543}, abstract = {

This study asked whether operant conditioning of the H-reflex can modify locomotion in spinal cord-injured rats. Midthoracic transection of the right lateral column of the spinal cord produced a persistent asymmetry in the muscle activity underlying treadmill locomotion. The rats were then either exposed or not exposed to an H-reflex up-conditioning protocol that greatly increased right soleus motoneuron response to primary afferent input, and locomotion was reevaluated. H-reflex up-conditioning increased the right soleus burst and corrected the locomotor asymmetry. In contrast, the locomotor asymmetry persisted in the control rats. These results suggest that appropriately selected reflex conditioning protocols might improve function in people with partial spinal cord injuries. Such protocols might be especially useful when significant regeneration becomes possible and precise methods for reeducating the regenerated spinal cord neurons and synapses are needed for restoring effective function.

}, keywords = {H-reflex conditioning, Learning, Locomotion, Memory, Motor control, Rehabilitation, spinal cord injury, spinal cord plasticity}, issn = {1529-2401}, doi = {10.1523/JNEUROSCI.2198-06.2006}, url = {http://www.ncbi.nlm.nih.gov/pubmed/17135415}, author = {Yi Chen and Xiang Yang Chen and Jakeman, Lyn B. and Lu Chen and Stokes, Bradford T. and Jonathan Wolpaw} } @article {3194, title = {The interaction of a new motor skill and an old one: H-reflex conditioning and locomotion in rats.}, journal = {The Journal of neuroscience : the official journal of the Society for Neuroscience}, volume = {25}, year = {2005}, month = {07/2005}, pages = {6898{\textendash}6906}, abstract = {New and old motor skills can interfere with each other or interact in other ways. Because each skill entails a distributed pattern of activity-dependent plasticity, investigation of their interactions is facilitated by simple models. In a well characterized model of simple learning, rats and monkeys gradually change the size of the H-reflex, the electrical analog of the spinal stretch reflex. This study evaluates in normal rats the interactions of this new skill of H-reflex conditioning with the old well established skill of overground locomotion. In rats in which the soleus H-reflex elicited in the conditioning protocol (i.e., the conditioning H-reflex) had been decreased by down-conditioning, the H-reflexes elicited during the stance and swing phases of locomotion (i.e., the locomotor H-reflexes) were also smaller. Similarly, in rats in which the conditioning H-reflex had been increased by up-conditioning, the locomotor H-reflexes were also larger. Soleus H-reflex conditioning did not affect the duration, length, or right/left symmetry of the step cycle. However, the conditioned change in the stance H-reflex was positively correlated with change in the amplitude of the soleus locomotor burst, and the correlation was consistent with current estimates of the contribution of primary afferent input to the burst. Although H-reflex conditioning and locomotion did not interfere with each other, H-reflex conditioning did affect how locomotion was produced: it changed soleus burst amplitude and may have induced compensatory changes in the activity of other muscles. These results illustrate and clarify the subtlety and complexity of skill interactions. They also suggest that H-reflex conditioning might be used to improve the abnormal locomotion produced by spinal cord injury or other disorders of supraspinal control.}, keywords = {H-reflex conditioning, Learning, Locomotion, memory consolidation, Motor control, Rehabilitation, spinal cord plasticity}, issn = {1529-2401}, doi = {10.1523/JNEUROSCI.1684-05.2005}, url = {http://www.ncbi.nlm.nih.gov/pubmed/16033899}, author = {Yi Chen and Xiang Yang Chen and Jakeman, Lyn B. and Gerwin Schalk and Stokes, Bradford T. and Jonathan Wolpaw} }