03911nas a2200361   4500008004100000022001400041245007800055210006900133260001300202300001400215490000800229520287700237653001203114653001303126653002503139653001003164653002603174653001303200653001303213653000903226653001803235653002403253653000903277653002503286653001603311100001303327700001303340700001303353700002103366700002203387700002403409856011603433       2024                        eng d  a1469-779300aMotor learning changes the axon initial segment of the spinal motoneuron.0 aMotor learning changes the axon initial segment of the spinal mo  c2024 May  a2107-21260 v6023 a<p>We are studying the mechanisms of H-reflex operant conditioning, a simple form of learning. Modelling studies in the literature and our previous data suggested that changes in the axon initial segment (AIS) might contribute. To explore this, we used blinded quantitative histological and immunohistochemical methods to study in adult rats the impact of H-reflex conditioning on the AIS of the spinal motoneuron that produces the reflex. Successful, but not unsuccessful, H-reflex up-conditioning was associated with greater AIS length and distance from soma; greater length correlated with greater H-reflex increase. Modelling studies in the literature suggest that these increases may increase motoneuron excitability, supporting the hypothesis that they may contribute to H-reflex increase. Up-conditioning did not affect AIS ankyrin G (AnkG) immunoreactivity (IR), p-p38 protein kinase IR, or GABAergic terminals. Successful, but not unsuccessful, H-reflex down-conditioning was associated with more GABAergic terminals on the AIS, weaker AnkG-IR, and stronger p-p38-IR. More GABAergic terminals and weaker AnkG-IR correlated with greater H-reflex decrease. These changes might potentially contribute to the positive shift in motoneuron firing threshold underlying H-reflex decrease; they are consistent with modelling suggesting that sodium channel change may be responsible. H-reflex down-conditioning did not affect AIS dimensions. This evidence that AIS plasticity is associated with and might contribute to H-reflex conditioning adds to evidence that motor learning involves both spinal and brain plasticity, and both neuronal and synaptic plasticity. AIS properties of spinal motoneurons are likely to reflect the combined influence of all the motor skills that share these motoneurons. KEY POINTS: Neuronal action potentials normally begin in the axon initial segment (AIS). AIS plasticity affects neuronal excitability in development and disease. Whether it does so in learning is unknown. Operant conditioning of a spinal reflex, a simple learning model, changes the rat spinal motoneuron AIS. Successful, but not unsuccessful, H-reflex up-conditioning is associated with greater AIS length and distance from soma. Successful, but not unsuccessful, down-conditioning is associated with more AIS GABAergic terminals, less ankyrin G, and more p-p38 protein kinase. The associations between AIS plasticity and successful H-reflex conditioning are consistent with those between AIS plasticity and functional changes in development and disease, and with those predicted by modelling studies in the literature. Motor learning changes neurons and synapses in spinal cord and brain. Because spinal motoneurons are the final common pathway for behaviour, their AIS properties probably reflect the combined impact of all the behaviours that use these motoneurons.</p>10aAnimals10aAnkyrins10aAxon Initial Segment10aAxons10aConditioning, Operant10aH-Reflex10aLearning10aMale10aMotor Neurons10aNeuronal Plasticity10aRats10aRats, Sprague-Dawley10aSpinal Cord1 aWang, Yu1 aChen, Yi1 aChen, Lu1 aHerron, Bruce, J1 aChen, Xiang, Yang1 aWolpaw, Jonathan, R  uhttps://www.neurotechcenter.org/publications/2024/motor-learning-changes-axon-initial-segment-spinal-motoneuron00805nas a2200229   4500008004100000022001400041245013800055210006900193260001300262300000800275490000800283653002600291653001300317653001100330653002100341653001100362653001600373653002500389100002000414700002200434856011900456       2024                        eng d  a1872-895200aOperant up-conditioning of the soleus cutaneous reflex to non-noxious stimuli in a person with chronic incomplete spinal cord injury.0 aOperant upconditioning of the soleus cutaneous reflex to nonnoxi  c2024 Jan  a1-30 v15710aConditioning, Operant10aH-Reflex10aHumans10aMuscle, Skeletal10aReflex10aSpinal Cord10aSpinal Cord Injuries1 aPhipps, Alan, M1 aThompson, Aiko, K  uhttps://www.neurotechcenter.org/publications/2024/operant-conditioning-soleus-cutaneous-reflex-non-noxious-stimuli02285nas a2200253   4500008004100000022001400041245007600055210006900131260001200200300001400212490000800226520146600234653001001700653002901710653001301739653001101752653002101763653002201784653004401806100002001850700002401870700002201894856011501916       2023                        eng d  a1432-110600aEffects of active and sham tDCS on the soleus H-reflex during standing.0 aEffects of active and sham tDCS on the soleus Hreflex during sta  c06/2023  a1611-16220 v2413 a<p>Weak transcranial direct current stimulation (tDCS) is known to affect corticospinal excitability and enhance motor skill acquisition, whereas its effects on spinal reflexes in actively contracting muscles are yet to be established. Thus, in this study, we examined the acute effects of Active and Sham tDCS on the soleus H-reflex during standing. In fourteen adults without known neurological conditions, the soleus H-reflex was repeatedly elicited at just above M-wave threshold throughout 30 min of Active (N = 7) or Sham (N = 7) 2-mA tDCS over the primary motor cortex in standing. The maximum H-reflex (H) and M-wave (M) were also measured before and immediately after 30 min of tDCS. The soleus H-reflex amplitudes became significantly larger (by 6%) ≈1 min into Active or Sham tDCS and gradually returned toward the pre-tDCS values, on average, within 15 min. With Active tDCS, the amplitude reduction from the initial increase appeared to occur more swiftly than with Sham tDCS. An acute temporary increase in the soleus H-reflex amplitude within the first minute of Active and Sham tDCS found in this study indicates a previously unreported effect of tDCS on the H-reflex excitability. The present study suggests that neurophysiological characterization of Sham tDCS effects is just as important as investigating Active tDCS effects in understanding and defining acute effects of tDCS on the excitability of spinal reflex pathways.</p>10aAdult10aEvoked Potentials, Motor10aH-Reflex10aHumans10aMuscle, Skeletal10aStanding Position10aTranscranial Direct Current Stimulation1 aMcCane, Lynn, M1 aWolpaw, Jonathan, R1 aThompson, Aiko, K  uhttps://www.neurotechcenter.org/publications/2023/effects-active-and-sham-tdcs-soleus-h-reflex-during-standing03030nas a2200265   4500008004100000022001400041245016500055210006900220260001600289490000700305520208500312653002502397653002102422653001302443653001102456653002102467653002202488653002602510100002502536700001702561700002202578700002202600700002202622856012002644       2023                        eng d  a1741-255200aMethods for automated delineation and assessment of EMG responses evoked by peripheral nerve stimulation in diagnostic and closed-loop therapeutic applications.0 aMethods for automated delineation and assessment of EMG response  c2023 Jul 210 v203 a<p>Surface electromyography measurements of the Hoffmann (H-) reflex are essential in a wide range of neuroscientific and clinical applications. One promising emerging therapeutic application is H-reflex operant conditioning, whereby a person is trained to modulate the H-reflex, with generalized beneficial effects on sensorimotor function in chronic neuromuscular disorders. Both traditional diagnostic and novel realtime therapeutic applications rely on accurate definitions of the H-reflex and M-wave temporal bounds, which currently depend on expert case-by-case judgment. The current study automates such judgments.Our novel wavelet-based algorithm automatically determines temporal extent and amplitude of the human soleus H-reflex and M-wave. In each of 20 participants, the algorithm was trained on data from a preliminary 3 or 4 min recruitment-curve measurement. Output was evaluated on parametric fits to subsequent sessions' recruitment curves (92 curves across all participants) and on the conditioning protocol's subsequent baseline trials (∼1200 per participant) performed near. Results were compared against the original temporal bounds estimated at the time, and against retrospective estimates made by an expert 6 years later.Automatic bounds agreed well with manual estimates: 95% lay within ±2.5 ms. The resulting H-reflex magnitude estimates showed excellent agreement (97.5% average across participants) between automatic and retrospective bounds regarding which trials would be considered successful for operant conditioning. Recruitment-curve parameters also agreed well between automatic and manual methods: 95% of the automatic estimates of the current required to elicitfell within±1.4%of the retrospective estimate; for the 'threshold' current that produced an M-wave 10% of maximum, this value was±3.5%.Such dependable automation of M-wave and H-reflex definition should make both established and emerging H-reflex protocols considerably less vulnerable to inter-personnel variability and human error, increasing translational potential.</p>10aElectric Stimulation10aElectromyography10aH-Reflex10aHumans10aMuscle, Skeletal10aPeripheral Nerves10aRetrospective Studies1 aMcKinnon, Michael, L1 aHill, Jeremy1 aCarp, Jonathan, S1 aDellenbach, Blair1 aThompson, Aiko, K  uhttps://www.neurotechcenter.org/publications/2023/methods-automated-delineation-and-assessment-emg-responses-evoked03130nas a2200313   4500008004100000022001400041245013900055210006900194260001500263520206900278653002002347653002602367653002102393653002202414653001302436653001102449653002702460653002502487100001702512700001702529700001902546700002402565700002302589700002102612700001402633700002402647700002202671856012302693       2022                        eng d  a1940-087X00aThe Evoked Potential Operant Conditioning System (EPOCS): A Research Tool and an Emerging Therapy for Chronic Neuromuscular Disorders.0 aEvoked Potential Operant Conditioning System EPOCS A Research To  c2022 08 253 a<p>The Evoked Potential Operant Conditioning System (EPOCS) is a software tool that implements protocols for operantly conditioning stimulus-triggered muscle responses in people with neuromuscular disorders, which in turn can improve sensorimotor function when applied appropriately. EPOCS monitors the state of specific target muscles-e.g., from surface electromyography (EMG) while standing, or from gait cycle measurements while walking on a treadmill-and automatically triggers calibrated stimulation when pre-defined conditions are met. It provides two forms of feedback that enable a person to learn to modulate the targeted pathway's excitability. First, it continuously monitors ongoing EMG activity in the target muscle, guiding the person to produce a consistent level of activity suitable for conditioning. Second, it provides immediate feedback of the response size following each stimulation and indicates whether it has reached the target value. To illustrate its use, this article describes a protocol through which a person can learn to decrease the size of the Hoffmann reflex-the electrically-elicited analog of the spinal stretch reflex-in the soleus muscle. Down-conditioning this pathway's excitability can improve walking in people with spastic gait due to incomplete spinal cord injury. The article demonstrates how to set up the equipment; how to place stimulating and recording electrodes; and how to use the free software to optimize electrode placement, measure the recruitment curve of direct motor and reflex responses, measure the response without operant conditioning, condition the reflex, and analyze the resulting data. It illustrates how the reflex changes over multiple sessions and how walking improves. It also discusses how the system can be applied to other kinds of evoked responses and to other kinds of stimulation, e.g., motor evoked potentials to transcranial magnetic stimulation; how it can address various clinical problems; and how it can support research studies of sensorimotor function in health and disease.</p>10aChronic Disease10aConditioning, Operant10aElectromyography10aEvoked Potentials10aH-Reflex10aHumans10aNeuromuscular Diseases10aSpinal Cord Injuries1 aHill, Jeremy1 aGupta, Disha1 aEftekhar, Amir1 aBrangaccio, Jodi, A1 aNorton, James, J S1 aMcLeod, Michelle1 aFake, Tim1 aWolpaw, Jonathan, R1 aThompson, Aiko, K  uhttps://www.neurotechcenter.org/publications/2022/evoked-potential-operant-conditioning-system-epocs-research-tool-and02454nas a2200265   4500008004100000022001400041245007300055210006900128260001200197300001400209490000800223520163500231653001001866653001601876653002101892653001301913653001101926653002001937653002101957100001801978700002401996700002602020700002202046856012002068       2022                        eng d  a1432-110600aSoleus H-reflex modulation during a double-legged drop landing task.0 aSoleus Hreflex modulation during a doublelegged drop landing tas  c04/2022  a1093-11030 v2403 a<p>Muscle spindle afferent feedback is modulated during different phases of locomotor tasks in a way that facilitates task goals. However, only a few studies have studied H-reflex modulation during landing. This study aimed to characterize soleus (SOL) H-reflex modulation during the flight and early landing period of drop landings. Since landing presumably involves a massive increase in spindle afferent firing due to rapid SOL muscle stretching, we hypothesized H-reflex size would decrease near landing reflecting neural modulation to prevent excessive motoneuron excitation. The soleus H-reflex was recorded during drop landings from a 30 cm height in nine healthy adults. Electromyography (SOL, tibialis anterior (TA), medial gastrocnemius, and vastus lateralis), ankle and knee joint motion and ground reaction force were recorded during landings. Tibial nerve stimulation was timed to elicit H-reflexes during the flight and early ground contact period (five 30 ms Bins from 90 ms before to 60 ms after landing). The H-reflexes recorded after landing (0-30 and 30-60 ms) were significantly smaller (21-36% less) than that recorded during the flight periods (90-0 ms before ground contact; P ≤ 0.004). The decrease in H-reflex size not occurring until after ground contact indicates a time-critical modulation of reflex gain during the last 30 ms of flight (i.e., time of tibial nerve stimulation). H-reflex size reduction after ground contact supports a probable neural strategy to prevent excessive reflex-mediated muscle activation and thereby facilitates appropriate musculotendon and joint stiffness.</p>10aAdult10aAnkle Joint10aElectromyography10aH-Reflex10aHumans10aMuscle Spindles10aMuscle, Skeletal1 aLyle, Mark, A1 aMcLeod, Michelle, M1 aPouliot, Bridgette, A1 aThompson, Aiko, K  uhttps://www.neurotechcenter.org/publications/2022/soleus-h-reflex-modulation-during-double-legged-drop-landing-task02570nas a2200325   4500008004100000022001400041245013800055210006900193260001200262300001100274490000800285520150800293653002601801653002601827653001601853653001301869653001101882653003101893100002001924700002301944700002001967700002001987700001802007700002302025700001902048700001902067700002402086700001902110856011502129       2020                        eng d  a1873-423500aBreathable, large-area epidermal electronic systems for recording electromyographic activity during operant conditioning of H-reflex.0 aBreathable largearea epidermal electronic systems for recording   c10/2020  a1124040 v1653 a<p>Operant conditioning of Hoffmann's reflex (H-reflex) is a non-invasive and targeted therapeutic intervention for patients with movement disorders following spinal cord injury. The reflex-conditioning protocol uses electromyography (EMG) to measure reflexes from specific muscles elicited using transcutaneous electrical stimulation. Despite recent advances in wearable electronics, existing EMG systems that measure muscle activity for operant conditioning of spinal reflexes still use rigid metal electrodes with conductive gels and aggressive adhesives, while requiring precise positioning to ensure reliability of data across experimental sessions. Here, we present the first large-area epidermal electronic system (L-EES) and demonstrate its use in every step of the reflex-conditioning protocol. The L-EES is a stretchable and breathable composite of nanomembrane electrodes (16 electrodes in a four by four array), elastomer, and fabric. The nanomembrane electrode array enables EMG recording from a large surface area on the skin and the breathable elastomer with fabric is biocompatible and comfortable for patients. We show that L-EES can record direct muscle responses (M-waves) and H-reflexes, both of which are comparable to those recorded using conventional EMG recording systems. In addition, L-EES may improve the reflex-conditioning protocol; it has potential to automatically optimize EMG electrode positioning, which may reduce setup time and error across experimental sessions.</p>10aBiosensing Techniques10aConditioning, Operant10aElectronics10aH-Reflex10aHumans10aReproducibility of Results1 aKwon, Young-Tae1 aNorton, James, J S1 aCutrone, Andrew1 aLim, Hyo-Ryoung1 aKwon, Shinjae1 aChoi, Jeongmoon, J1 aKim, Hee, Seok1 aJang, Young, C1 aWolpaw, Jonathan, R1 aYeo, Woon-Hong  uhttps://www.neurotechcenter.org/publications/2020/breathable-large-area-epidermal-electronic-systems-recording01263nas a2200253   4500008004100000245006000041210005900101260001200160490000800172520057900180653000800759653000800767653001300775653002500788653001900813100001400832700001500846700001500861700001500876700001700891700001200908700001700920856007200937       2020                        eng d00aOperant Condition of the Flexor Carpi Radialis H-reflex0 aOperant Condition of the Flexor Carpi Radialis Hreflex  c12/20200 v1013 aOperant conditioning of the largely monosynaptic H-reflex is a targeted and non-invasive therapeutic intervention for people with motor dysfunction after spinal cord injury and possibly stroke.1,2,3 It can complement other therapies and has no known adverse side effects. To date, H-reflex operant conditioning has focused on the leg. Here, we extend it to the arm by asking participants to either increase or decrease the flexor carpi radialis (FCR) H-reflex. In addition, we examine concurrent changes in brain activity by recording electroencephalographic activity (EEG).10aBCI10aFCR10aH-Reflex10aoperant conditioning10aRehabilitation1 aNorton, J1 aVaughan, T1 aGemoets, D1 aHeckman, S1 aToliou, S.D.1 aCarp, J1 aWolpaw, J.R.  uhttps://www.archives-pmr.org/article/S0003-9993(20)31081-9/abstract02519nas a2200277   4500008004100000022001400041245009000055210006900145260001200214490000700226520169200233653003401925653001801959653001301977653002501990653003002015100001702045700001502062700001502077700001302092700001702105700001502122700002102137700001802158856006502176       2018                        eng d  a1662-453X00aEffects of Sensorimotor Rhythm Modulation on the Human Flexor Carpi Radialis H-Reflex0 aEffects of Sensorimotor Rhythm Modulation on the Human Flexor Ca  c07/20180 v123 aPeople can learn over training sessions to increase or decrease sensorimotor rhythms (SMRs) in the electroencephalogram (EEG). Activity-dependent brain plasticity is thought to guide spinal plasticity during motor skill learning; thus, SMR training may affect spinal reflexes and thereby influence motor control. To test this hypothesis, we investigated the effects of learned mu (8–13 Hz) SMR modulation on the flexor carpi radialis (FCR) H-reflex in 6 subjects with no known neurological conditions and 2 subjects with chronic incomplete spinal cord injury (SCI). All subjects had learned and practiced over more than 10 < 30-min training sessions to increase (SMR-up trials) and decrease (SMR-down trials) mu-rhythm amplitude over the hand/arm area of left sensorimotor cortex with ≥80% accuracy. Right FCR H-reflexes were elicited at random times during SMR-up and SMR-down trials, and in between trials. SMR modulation affected H-reflex size. In all the neurologically normal subjects, the H-reflex was significantly larger [116% ± 6 (mean ± SE)] during SMR-up trials than between trials, and significantly smaller (92% ± 1) during SMR-down trials than between trials (p < 0.05 for both, paired t-test). One subject with SCI showed similar H-reflex size dependence (high for SMR-up trials, low for SMR-down trials): the other subject with SCI showed no dependence. These results support the hypothesis that SMR modulation has predictable effects on spinal reflex excitability in people who are neurologically normal; they also suggest that it might be used to enhance therapies that seek to improve functional recovery in some individuals with SCI or other CNS disorders.

10abrain-computer interface (BC)10aEEG mu-rhythm10aH-Reflex10aSpinal Cord Injuries10atask-dependent adaptation1 aThompson, AK1 aCarruth, H1 aHaywood, R1 aHill, NJ1 aSarnacki, WA1 aMcCane, LM1 aWolpaw, Jonathan1 aMcFarland, DJ  uhttps://www.frontiersin.org/article/10.3389/fnins.2018.0050501870nas a2200265   4500008004100000022001400041245008400055210006900139260001200208300001200220490000700232520108800239653002501327653001301352653002701365653002501392653001501417653001901432653001801451100001601469700001601485700001801501700002101519856006401540       2018                        eng d  a1878-747900aRetraining Reflexes: Clinical Translation of Spinal Reflex Operant Conditioning0 aRetraining Reflexes Clinical Translation of Spinal Reflex Operan  c07/2018  a669-6830 v153 aNeurological disorders, such as spinal cord injury, stroke, traumatic brain injury, cerebral palsy, and multiple sclerosis cause motor impairments that are a huge burden at the individual, family, and societal levels. Spinal reflex abnormalities contribute to these impairments. Spinal reflex measurements play important roles in characterizing and monitoring neurological disorders and their associated motor impairments, such as spasticity, which affects nearly half of those with neurological disorders. Spinal reflexes can also serve as therapeutic targets themselves. Operant conditioning protocols can target beneficial plasticity to key reflex pathways; they can thereby trigger wider plasticity that improves impaired motor skills, such as locomotion. These protocols may complement standard therapies such as locomotor training and enhance functional recovery. This paper reviews the value of spinal reflexes and the therapeutic promise of spinal reflex operant conditioning protocols; it also considers the complex process of translating this promise into clinical reality.10aclinical translation10aH-Reflex10aneurological disorders10aoperant conditioning10aplasticity10aRehabilitation10aspinal reflex1 aEftekhar, A1 aNorton, JJS1 aMcDonough, CM1 aWolpaw, Jonathan  uhttps://link.springer.com/article/10.1007/s13311-018-0643-202131nas a2200253   4500008004100000245007200041210006900113260000900182300001400191490000700205520141800212653001301630653001901643653002501662653001501687653001901702653001601721100001301737700001301750700001301763700002201776700002101798856005801819       2017                        eng d00aWhy New Spinal Cord Plasticity Does Not Disrupt Old Motor Behaviors0 aWhy New Spinal Cord Plasticity Does Not Disrupt Old Motor Behavi  cJuly  a8198-82060 v373 aWhen new motor learning changes the spinal cord, old behaviors are not impaired; their key features are preserved by additional compensatory plasticity. To explore the mechanisms responsible for this compensatory plasticity, we transected the spinal dorsal ascending tract before or after female rats acquired a new behavior—operantly conditioned increase or decrease in the right soleus H-reflex—and examined an old behavior—locomotion. Neither spinal dorsal ascending tract transection nor H-reflex conditioning alone impaired locomotion. Nevertheless, when spinal dorsal ascending tract transection and H-reflex conditioning were combined, the rats developed a limp and a tilted posture that correlated in direction and magnitude with the H-reflex change. When the right H-reflex was increased by conditioning, the right step lasted longer than the left and the right hip was higher than the left; when the right H-reflex was decreased by conditioning, the opposite occurred. These results indicate that ascending sensory input guides the compensatory plasticity that normally prevents the plasticity underlying H-reflex change from impairing locomotion. They support the concept of the state of the spinal cord as a negotiated equilibrium that reflects the concurrent influences of all the behaviors in an individual's repertoire; and they support the new therapeutic strategies this concept introduces.10aH-Reflex10amotor learning10aoperant conditioning10aplasticity10aRehabilitation10aSpinal Cord1 aChen, Yi1 aChen, Lu1 aWang, Yu1 aChen, Xiang, Yang1 aWolpaw, Jonathan  uhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC5566867/02314nas a2200229   4500008004100000022001400041245010300055210006900158260001200227300001200239490000800251520162300259653002901882653001101911653001301922653001801935653001601953100002501969700002101994700002102015856004802036       2015                        eng d  a1522-159800aElectrocorticographic activity over sensorimotor cortex and motor function in awake behaving rats.0 aElectrocorticographic activity over sensorimotor cortex and moto  c04/2015  a2232-410 v1133 a<p>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.</p>10abrain-computer interface10acortex10aH-Reflex10aMotor control10aSpinal Cord1 aBoulay, Chadwick, B.1 aChen, Xiang Yang1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/2563207602012nas a2200229   4500008004100000022001400041245004900055210004800104260001200152300001100164490000800175520137600183653003401559653001301593653002501606653001901631653002301650653001801673100002201691700002101713856004801734       2015                        eng d  a1875-785500aTargeted neuroplasticity for rehabilitation.0 aTargeted neuroplasticity for rehabilitation  c03/2015  a157-720 v2183 a<p>An operant-conditioning protocol that bases reward on the electromyographic response produced by a specific CNS pathway can change that pathway. For example, in both animals and people, an operant-conditioning protocol can increase or decrease the spinal stretch reflex or its electrical analog, the H-reflex. Reflex change is associated with plasticity in the pathway of the reflex as well as elsewhere in the spinal cord and brain. Because these pathways serve many different behaviors, the plasticity produced by this conditioning can change other behaviors. Thus, in animals or people with partial spinal cord injuries, appropriate reflex conditioning can improve locomotion. Furthermore, in people with spinal cord injuries, appropriate reflex conditioning can trigger widespread beneficial plasticity. This wider plasticity appears to reflect an iterative process through which the multiple behaviors in the individual's repertoire negotiate the properties of the spinal neurons and synapses that they all use. Operant-conditioning protocols are a promising new therapeutic method that could complement other rehabilitation methods and enhance functional recovery. Their successful use requires strict adherence to appropriately designed procedures, as well as close attention to accommodating and engaging the individual subject in the conditioning process.</p>10aactivity-dependent plasticity10aH-Reflex10aoperant conditioning10aRehabilitation10aspinal cord injury10aspinal reflex1 aThompson, Aiko, K1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/2589013602675nas a2200325   4500008004100000022001400041245010000055210006900155260001200224300001200236490000800248520178700256653001202043653002602055653001102081653001302092653001302105653001502118653000902133653000902142653002502151653002502176100001302201700001302214700001902227700001302246700002102259700002102280856004802301       2014                        eng d  a1522-159800aLocomotor impact of beneficial or nonbeneficial H-reflex conditioning after spinal cord injury.0 aLocomotor impact of beneficial or nonbeneficial Hreflex conditio  c03/2014  a1249-580 v1113 aWhen new motor learning changes neurons and synapses in the spinal cord, it may affect previously learned behaviors that depend on the same spinal neurons and synapses. To explore these effects, we used operant conditioning to strengthen or weaken the right soleus H-reflex pathway in rats in which a right spinal cord contusion had impaired locomotion. When up-conditioning increased the H-reflex, locomotion improved. Steps became longer, and step-cycle asymmetry (i.e., limping) disappeared. In contrast, when down-conditioning decreased the H-reflex, locomotion did not worsen. Steps did not become shorter, and asymmetry did not increase. Electromyographic and kinematic analyses explained how H-reflex increase improved locomotion and why H-reflex decrease did not further impair it. Although the impact of up-conditioning or down-conditioning on the H-reflex pathway was still present during locomotion, only up-conditioning affected the soleus locomotor burst. Additionally, compensatory plasticity apparently prevented the weaker H-reflex pathway caused by down-conditioning from weakening the locomotor burst and further impairing locomotion. The results support the hypothesis that the state of the spinal cord is a "negotiated equilibrium" that serves all the behaviors that depend on it. When new learning changes the spinal cord, old behaviors undergo concurrent relearning that preserves or improves their key features. Thus, if an old behavior has been impaired by trauma or disease, spinal reflex conditioning, by changing a specific pathway and triggering a new negotiation, may enable recovery beyond that achieved simply by practicing the old behavior. Spinal reflex conditioning protocols might complement other neurorehabilitation methods and enhance recovery.10aAnimals10aConditioning, Operant10aFemale10aH-Reflex10aLearning10aLocomotion10aMale10aRats10aRats, Sprague-Dawley10aSpinal Cord Injuries1 aChen, Yi1 aChen, Lu1 aLiu, Rongliang1 aWang, Yu1 aChen, Xiang Yang1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/2437128802145nas a2200217   4500008004100000022001400041245008500055210006900140260001200209300000700221490000600228520150000234653001301734653002401747653001501771653002301786653002701809100002201836700002101858856004801879       2014                        eng d  a1662-514500aOperant conditioning of spinal reflexes: from basic science to clinical therapy.0 aOperant conditioning of spinal reflexes from basic science to cl  c03/2014  a250 v83 aNew appreciation of the adaptive capabilities of the nervous system, recent recognition that most spinal cord injuries are incomplete, and progress in enabling regeneration are generating growing interest in novel rehabilitation therapies. Here we review the 35-year evolution of one promising new approach, operant conditioning of spinal reflexes. This work began in the late 1970's as basic science; its purpose was to develop and exploit a uniquely accessible model for studying the acquisition and maintenance of a simple behavior in the mammalian central nervous system (CNS). The model was developed first in monkeys and then in rats, mice, and humans. Studies with it showed that the ostensibly simple behavior (i.e., a larger or smaller reflex) rests on a complex hierarchy of brain and spinal cord plasticity; and current investigations are delineating this plasticity and its interactions with the plasticity that supports other behaviors. In the last decade, the possible therapeutic uses of reflex conditioning have come under study, first in rats and then in humans. The initial results are very exciting, and they are spurring further studies. At the same time, the original basic science purpose and the new clinical purpose are enabling and illuminating each other in unexpected ways. The long course and current state of this work illustrate the practical importance of basic research and the valuable synergy that can develop between basic science questions and clinical needs.10aH-Reflex10alearning and memory10aLocomotion10aspinal cord injury10aspinal cord plasticity1 aThompson, Aiko, K1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/2467244101203nas a2200277   4500008004100000022001400041245009000055210006900145260001200214300001000226490000700236520041500243653001200658653002600670653001300696653001100709653001700720653002100737653002400758653001100782653001600793653002500809100002200834700002100856856004800877       2014                        eng d  a1538-300800aThe simplest motor skill: mechanisms and applications of reflex operant conditioning.0 asimplest motor skill mechanisms and applications of reflex opera  c04/2014  a82-900 v423 aOperant conditioning protocols can change spinal reflexes gradually, which are the simplest behaviors. This article summarizes the evidence supporting two propositions: that these protocols provide excellent models for defining the substrates of learning and that they can induce and guide plasticity to help restore skills, such as locomotion, that have been impaired by spinal cord injury or other disorders.10aAnimals10aConditioning, Operant10aH-Reflex10aHumans10aMotor Skills10aMuscle, Skeletal10aNeuronal Plasticity10aReflex10aSpinal Cord10aSpinal Cord Injuries1 aThompson, Aiko, K1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/2450873801519nas a2200301   4500008004100000022001400041245009500055210006900150260001200219300001400231490001700245520064100262653001300903653002400916653001500940653001500955653002400970653001900994653002301013100002101036700001301057700001301070700001901083700002301102700002301125700002101148856004801169       2010                        eng d  a1749-663200aReflex conditioning: a new strategy for improving motor function after spinal cord injury.0 aReflex conditioning a new strategy for improving motor function   c06/2010  aE12–E210 v1198 Suppl 13 aSpinal reflex conditioning changes reflex size, induces spinal cord plasticity, and modifies locomotion. Appropriate reflex conditioning can improve walking in rats after spinal cord injury (SCI). Reflex conditioning offers a new therapeutic strategy for restoring function in people with SCI. This approach can address the specific deficits of individuals with SCI by targeting specific reflex pathways for increased or decreased responsiveness. In addition, once clinically significant regeneration can be achieved, reflex conditioning could provide a means of reeducating the newly (and probably imperfectly) reconnected spinal cord.10aH-Reflex10alearning and memory10aLocomotion10aplasticity10areflex conditioning10aRehabilitation10aspinal cord injury1 aChen, Xiang Yang1 aChen, Yi1 aWang, Yu1 aThompson, Aiko1 aCarp, Jonathan, S.1 aSegal, Richard, L.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/2059053402476nas a2200241   4500008004100000022001400041245011900055210006900174260001200243300001600255490000700271520173900278653001302017653001902030653001602049653002502065653001502090653001602105100002302121700002102144700002102165856004802186       2009                        eng d  a1529-240100aAcquisition of a simple motor skill: task-dependent adaptation plus long-term change in the human soleus H-reflex.0 aAcquisition of a simple motor skill taskdependent adaptation plu  c05/2009  a5784–57920 v293 aActivity-dependent plasticity occurs throughout the CNS. However, investigations of skill acquisition usually focus on cortex. To expand the focus, we analyzed in humans the development of operantly conditioned H-reflex change, a simple motor skill that develops gradually and involves plasticity in both the brain and the spinal cord. Each person completed 6 baseline and 24 conditioning sessions over 10 weeks. In each conditioning session, the soleus H-reflex was measured while the subject was or was not asked to increase (HRup subjects) or decrease (HRdown subjects) it. When the subject was asked to change H-reflex size, immediate visual feedback indicated whether a size criterion had been satisfied. Over the 24 conditioning sessions, H-reflex size gradually increased in six of eight HRup subjects and decreased in eight of nine HRdown subjects, resulting in final sizes of 140 +/- 12 and 69 +/- 6% of baseline size, respectively. The final H-reflex change was the sum of within-session (i.e., task-dependent) adaptation and across-session (i.e., long-term) change. Task-dependent adaptation appeared within four to six sessions and persisted thereafter, averaging +13% in HRup subjects and -15% in HRdown subjects. In contrast, long-term change began after 10 sessions and increased gradually thereafter, reaching +27% in HRup subjects and -16% in HRdown subjects. Thus, the acquisition of H-reflex conditioning consists of two phenomena, task-dependent adaptation and long-term change, that together constitute the new motor skill. In combination with previous data, this new finding further elucidates the interaction of plasticity in brain and spinal cord that underlies the acquisition and maintenance of motor skills.10aH-Reflex10amotor learning10amotor skill10aoperant conditioning10aplasticity10aSpinal Cord1 aThompson, Aiko, K.1 aChen, Xiang Yang1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1942024602003nas a2200241   4500008004100000022001400041245007500055210006900130260001200199300001400211490000800225520132900233653001701562653001301579653001301592653001101605653001901616653001501635653001901650653002301669100002101692856004801713       2007                        eng d  a1748-170800aSpinal cord plasticity in acquisition and maintenance of motor skills.0 aSpinal cord plasticity in acquisition and maintenance of motor s  c02/2007  a155–1690 v1893 aThroughout normal life, activity-dependent plasticity occurs in the spinal cord as well as in brain. Like other central nervous system (CNS) plasticity, spinal cord plasticity can occur at numerous neuronal and synaptic sites and through a variety of mechanisms. Spinal cord plasticity is prominent early in life and contributes to mastery of standard behaviours like locomotion and rapid withdrawal from pain. Later in life, spinal cord plasticity has a role in acquisition and maintenance of new motor skills, and in compensation for peripheral and central changes accompanying ageing, disease and trauma. Mastery of the simplest behaviours is accompanied by complex spinal and supraspinal plasticity. This complexity is necessary, in order to preserve the complete behavioural repertoire, and is also inevitable, due to the ubiquity of activity-dependent CNS plasticity. Explorations of spinal cord plasticity are necessary for understanding motor skills. Furthermore, the spinal cord's comparative simplicity and accessibility makes it a logical starting point for studying skill acquisition. Induction and guidance of activity-dependent spinal cord plasticity will probably play an important role in realization of effective new rehabilitation methods for spinal cord injuries, cerebral palsy and other motor disorders.10aconditioning10aH-Reflex10aLearning10aMemory10amotor function10aplasticity10aRehabilitation10aspinal cord injury1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1725056602175nas a2200253   4500008004100000022001400041245008500055210006900140260001200209300001400221490000700235520145300242653003401695653000901729653001301738653001101751653001801762653001601780100001301796700002201809700002101831700002101852856004801873       2006                        eng d  a0953-816X00aMotor learning changes GABAergic terminals on spinal motoneurons in normal rats.0 aMotor learning changes GABAergic terminals on spinal motoneurons  c01/2006  a141–1500 v233 aThe 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.10aactivity-dependent plasticity10aGABA10aH-Reflex10aMemory10aMotor control10aSpinal Cord1 aWang, Yu1 aPillai, Shreejith1 aWolpaw, Jonathan1 aChen, Xiang Yang  uhttp://www.ncbi.nlm.nih.gov/pubmed/1642042402190nas a2200253   4500008004100000022001400041245009500055210006900150260001200219300001600231490000800247520145200255653001301707653001501720653001101735653001501746653001601761100002501777700001901802700002201821700002101843700002401864856004801888       2006                        eng d  a1388-245700aPlastic changes in the human H-reflex pathway at rest following skillful cycling training.0 aPlastic changes in the human Hreflex pathway at rest following s  c08/2006  a1682–16910 v1173 aOBJECTIVE:
The spinal cord is capable of activity-dependent plasticity, but the extent of its participation in human motor learning is not known. Here, we tested the hypothesis that acquisition of a locomotor-related skill modulates the pathway of the H-reflex, a measure of spinal cord excitability that is susceptible to plastic changes.
METHODS:
Subjects were tested on their ability to establish a constant cycling speed on a recumbent bike despite frequent changes in pedal resistance. The coefficient of variation of speed (CV(speed)) measured their ability to acquire this skill (decreasing CV(speed) with training reflects performance improvements). Soleus H-reflexes were taken at rest before and after cycling.
RESULTS:
Ability to establish a target speed increased and H-reflex size decreased more after cycling training involving frequent changes in pedal resistance that required calibrated locomotor compensatory action than with training involving constant pedal resistances and lesser compensation. The degree of performance improvement correlated with the reduction in the amplitude of the H-reflex.
CONCLUSIONS:
Skillful establishment of a constant cycling speed despite changing pedal resistances is associated with persistent modulation of activity in spinal pathways.
SIGNIFICANCE:
Recalibration of activity in the H-reflex pathway may be part of the control strategy required for locomotor-related skill acquisition.10aH-Reflex10aLocomotion10aMemory10aplasticity10aSpinal Cord1 aMazzocchio, Riccardo1 aKitago, Tomoko1 aLiuzzi, Gianpiero1 aWolpaw, Jonathan1 aCohen, Leonardo, G.  uhttp://www.ncbi.nlm.nih.gov/pubmed/1679333301877nas a2200253   4500008004100000022001400041245007900055210006900134260001200203300001400215490000800229520115300237653002201390653002401412653001901436653001301455653000801468653002301476100002101499700001301520700002101533700002101554856004801575       2002                        eng d  a0006-899300aCorticospinal tract transection reduces H-reflex circadian rhythm in rats.0 aCorticospinal tract transection reduces Hreflex circadian rhythm  c06/2002  a101–1080 v9423 aIn freely moving rats and monkeys, H-reflex amplitude displays a marked circadian variation without change in background motoneuron tone. In rats, the H-reflex is largest around noon and smallest around midnight. The present study evaluated in rats the effects on this rhythm of calibrated contusions of mid-thoracic spinal cord and mid-thoracic transection of specific spinal cord pathways. In 33 control rats, rhythm amplitude averaged 29.0(+/-2.6 S.E.)% of H-reflex amplitude. Contusion injuries at T8-9 that destroyed 53-88% of the white matter significantly reduced the rhythm to 18.9(+/-2.4)% of H-reflex amplitude. Transection of the ipsilateral lateral column, which contains the rubrospinal, vestibulospinal, and reticulospinal tracts, or bilateral transection of the dorsal column ascending tract did not affect rhythm amplitude or phase. In contrast, bilateral transection of the main corticospinal tract significantly reduced the rhythm to 14.7(+/-6.6)%. These results indicate that the H-reflex circadian rhythm depends in part on descending influence from the brain and that this influence is conveyed by the main corticospinal tract.10acircadian rhythms10acorticospinal tract10adiurnal rhythm10aH-Reflex10arat10aspinal cord injury1 aChen, Xiang Yang1 aChen, Lu1 aWolpaw, Jonathan1 aJakeman, Lyn, B.  uhttp://www.ncbi.nlm.nih.gov/pubmed/1203185802917nas a2200265   4500008004100000022001400041245009700055210006900152260001200221300001000233490000800243520213200251653002202383653001202405653002102417653001302438653001802451653002102469653000902490653004102499100001902540700002302559700002102582856004802603       2002                        eng d  a0165-027000aTemporal transformation of multiunit activity improves identification of single motor units.0 aTemporal transformation of multiunit activity improves identific  c02/2002  a87-980 v1143 a<p><span style="font-family: arial, helvetica, clean, sans-serif; font-size: 13px; line-height: 17px;">This report describes a temporally based method for identifying repetitive firing of motor units. This&nbsp;</span><span class="highlight" style="font-family: arial, helvetica, clean, sans-serif; font-size: 13px; line-height: 17px;">approach</span><span style="font-family: arial, helvetica, clean, sans-serif; font-size: 13px; line-height: 17px;">&nbsp;is ideally suited to spike trains with negative serially correlated inter-spike intervals (ISIs). It can also be applied to spike trains in which ISIs exhibit little serial correlation if their coefficient of variation (COV) is sufficiently low. Using a novel application of the Hough transform, this method (i.e. the modified Hough transform (MHT)) maps motor unit action potential (MUAP) firing times into a feature space with ISI and offset (defined as the latency from an arbitrary starting time to the first MUAP in the train) as dimensions. Each MUAP firing time corresponds to a pattern in the feature space that represents all possible MUAP trains with a firing at that time. Trains with stable ISIs produce clusters in the feature space, whereas randomly firing trains do not. The MHT provides a direct estimate of mean firing rate and its variability for the entire data segment, even if several individual MUAPs are obscured by firings from other motor units. Addition of this method to a shape-based classification&nbsp;</span><span class="highlight" style="font-family: arial, helvetica, clean, sans-serif; font-size: 13px; line-height: 17px;">approach</span><span style="font-family: arial, helvetica, clean, sans-serif; font-size: 13px; line-height: 17px;">&nbsp;markedly improved rejection of false positives using simulated data and identified spike trains in whole muscle electromyographic recordings from rats. The relative independence of the MHT from the need to correctly classify individual firings permits a global description of stable repetitive firing behavior that is complementary to shape-based approaches to MUAP classification.</span></p>10aAction Potentials10aAnimals10aElectromyography10aH-Reflex10aMotor Neurons10aMuscle, Skeletal10aRats10aSignal Processing, Computer-Assisted1 aSchalk, Gerwin1 aCarp, Jonathan, S.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1185004301678nas a2200277   4500008004100000022001400041245009700055210006900152260001200221300001000233490000800243520088300251653002201134653002101156653001301177653002501190653001601215653001501231653001801246653000801264100002301272700002101295700001501316700002101331856004801352       2001                        eng d  a0304-394000aEffects of chronic nerve cuff and intramuscular electrodes on rat triceps surae motor units.0 aEffects of chronic nerve cuff and intramuscular electrodes on ra  c10/2001  a1–40 v3123 aIn order to assess the long-term effects of implanted electrodes on motor unit properties, we studied triceps surae (TS) motor units in rats implanted for 3-10 months with a tibial nerve cuff electrode for H-reflex elicitation and intramuscular electrodes for recording TS electromyographic activity. Motor units with sag from implanted rats displayed greater tetanic force than those from unimplanted rats. Motor units without sag had shorter twitch contraction times. This disrupted the relationship between sag and contraction time that was always present in unimplanted rats. These differences were consistent with a small degree of muscle denervation and subsequent reinnervation. Further analyses ascribed this effect to the nerve cuff rather than to the intramuscular electrodes. Comparable changes in motor unit properties may occur in humans with implanted nerve cuffs.10achronic recording10acontraction time10aH-Reflex10aimplanted electrodes10amotor units10anerve cuff10areinnervation10asag1 aCarp, Jonathan, S.1 aChen, Xiang Yang1 aSheikh, H.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1157883102272nas a2200241   4500008004100000022001400041245007000055210006800125260001200193300001400205490000800219520158400227653001301811653002001824653002501844653001501869653001801884100002301902700002101925700001501946700002101961856004801982       2001                        eng d  a0014-481900aMotor unit properties after operant conditioning of rat H-reflex.0 aMotor unit properties after operant conditioning of rat Hreflex  c10/2001  a382–3860 v1403 aOperant conditioning of the H-reflex produces plasticity at several sites in the spinal cord, including the motoneuron. This study assessed whether this spinal cord plasticity is accompanied by changes in motor unit contractile properties. Thirty-one adult male Sprague-Dawley rats implanted for chronic recording of triceps surae electromyographic activity and H-reflex elicitation were exposed for at least 40 days to HRup or HRdown training, in which reward occurred when the H-reflex was greater than (12 HRup rats) or less than (12 HRdown rats) a criterion value, or continued under the control mode in which the H-reflex was simply measured (7 HRcon rats). At the end of H-reflex data collection, rats were anesthetized and the contractile properties of 797 single triceps surae motor units activated by intraaxonal (or intramyelin) current injection were determined. Motor units were classified as S, FR, Fint, or FF on the basis of sag and fatigue properties. Maximum tetanic force and twitch contraction time were also measured. HRdown rats exhibited a significant increase in the fatigue index of fast-twitch motor units. This resulted in a significant decrease in the percentage of Fint motor units and a significant increase in that of FR motor units. HRup conditioning had no effect on fatigue index. Neither HRup nor HRdown conditioning affected maximum tetanic force or twitch contraction time. These data are consistent with the hypothesis that conditioning mode-specific change in motoneuron firing patterns causes activity-dependent change in muscle properties.10aH-Reflex10amotor unit type10aoperant conditioning10aplasticity10atriceps surae1 aCarp, Jonathan, S.1 aChen, Xiang Yang1 aSheikh, H.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1168131402242nas a2200241   4500008004100000022001400041245008800055210006900143260001200212300001400224490000800238520154300246653002401789653001301813653001501826653001501841653001601856100002301872700002101895700001501916700002101931856004801952       2001                        eng d  a0014-481900aOperant conditioning of rat H-reflex affects motoneuron axonal conduction velocity.0 aOperant conditioning of rat Hreflex affects motoneuron axonal co  c01/2001  a269–2730 v1363 aThis study assessed the effects of operant conditioning of the H-reflex on motoneuron axonal conduction velocity in the rat. After measurement of the control H-reflex size, rats were either exposed for at least 40 days to the HRup or HRdown conditioning mode, in which reward occurred only if the soleus H-reflex was greater than (HRup mode) or less than (HRdown mode) a criterion or continued under the control condition (HRcon mode) in which the H-reflex was simply measured. We then measured axonal conduction velocity of triceps surae motor units of HRup, HRdown, and HRcon rats by stimulating the axon in the ventral root and recording from the tibial nerve. Conduction velocity was 8% less in successful HRdown rats than in HRcon rats (P=0.02). Conduction velocity in HRup rats and unsuccessful HRdown rats was not significantly different from that in HRcon rats. Since recording bypassed the intra-spinal portion of the motoneuron, the change was clearly in the axon. This decrease was similar to the 6% decrease previously found in successful HRdown monkeys. Unsuccessful HRdown rats and monkeys did not show this decrease. This result suggests that the mechanism of HRdown conditioning is similar in rats and monkeys and provides further support for the hypothesis that HRdown conditioning decreases motoneuron excitability by producing a positive shift in firing threshold. While traditional theories of learning emphasize synaptic plasticity, neuronal plasticity may also contribute to operantly conditioned behavioral changes.10aconduction velocity10aH-Reflex10amotoneuron10aplasticity10aSpinal Cord1 aCarp, Jonathan, S.1 aChen, Xiang Yang1 aSheikh, H.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1120629002143nas a2200217   4500008004100000022001400041245008000055210006900135260001200204300001400216490000800230520152500238653001701763653001301780653001101793653001501804653001601819100002101835700002101856856004801877       2001                        eng d  a0014-481900aOperant conditioning of rat H-reflex: effects on mean latency and duration.0 aOperant conditioning of rat Hreflex effects on mean latency and   c01/2001  a274–2790 v1363 aWe are currently studying the mechanisms of operantly conditioned changes in the H-reflex in the rat. Primate data suggest that H-reflex decrease is due to a positive shift in motoneuron firing threshold and a small decrease in the monosynaptic excitatory postsynaptic potential (EPSP), and that increase might be due to change in group-I oligosynaptic (especially disynaptic) input. To further evaluate the possibility of conditioned change in oligosynaptic input, we compared the mean latency (i.e., the average latency of the entire H-reflex) and the duration of control (i.e., pre-conditioning) H-reflexes with those of H-reflexes after up-conditioning or down-conditioning. Up-conditioning was associated with small, statistically significant increases in H-reflex mean latency [+0.11+/-0.05 (+/-SE) ms] and duration (+0.32+/-0.16 ms). The mean latency of the H-reflex increase (i.e., the part added to the H-reflex by up-conditioning) was 0.28+/-0.14 (+/-SE) ms greater than that of the control H-reflex. Down-conditioning had no significant effect on mean latency or duration. While these results indicate that operant conditioning does not greatly change H-reflex mean latency or duration, the effects detected with up-conditioning are consistent with the hypothesis that decreased inhibition, or increased excitation, by homonymous and heteronymous group-I oligosynaptic input contributes to the H-reflex increase produced by up-conditioning. Several other mechanisms might also account for these small effects.10aconditioning10aH-Reflex10aMemory10aplasticity10aSpinal Cord1 aWolpaw, Jonathan1 aChen, Xiang Yang  uhttp://www.ncbi.nlm.nih.gov/pubmed/1120629102520nas a2200253   4500008004100000022001400041245007700055210007100132260001200203300001400215490000700229520179900236653001302035653002502048653001502073653000802088653001802096653002302114100002102137700002102158700002002179700001902199856004802218       1999                        eng d  a0897-715100aOperant conditioning of H-reflex increase in spinal cord–injured rats.0 aOperant conditioning of Hreflex increase in spinal cord–injured   c02/1999  a175–1860 v163 aOperant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, is a new model for exploring the mechanisms of long-term supraspinal control over spinal cord function. Primates and rats can gradually increase (HRup conditioning mode) or decrease (HRdown conditioning mode) the H-reflex when reward is based on H-reflex amplitude. An earlier study indicated that HRdown conditioning of the soleus H-reflex in rats is impaired following contusion injury to thoracic spinal cord. The extent of impairment was correlated with the percent of white matter lost at the injury site. The present study investigated the effects of spinal cord injury on HRup conditioning. Soleus H-reflexes were elicited and recorded with chronically implanted electrodes from 14 rats that had been subjected to calibrated contusion injuries to the spinal cord at T8. At the lesion epicenter, 12-39% of the white matter remained. After control-mode data were collected, each rat was exposed to the HRup conditioning mode for 50 days. Final H-reflex amplitudes after HRup conditioning averaged 112% (+/-22% SD) of control. This value was significantly smaller than that for 13 normal rats exposed to HRup conditioning, in which final amplitude averaged 153% (+/-51%) SD of control. As previously reported for HRdown conditioning after spinal cord injury, success was inversely correlated with the severity of the injury as assessed by white matter preservation and by time to return of bladder function. HRup and HRdown conditioning are similarly sensitive to injury. These results further demonstrate that H-reflex conditioning is a sensitive measure of the long-term effects of injury on supraspinal control over spinal cord functions and could prove a valuable measure of therapeutic efficacy.10aH-Reflex10aoperant conditioning10aplasticity10arat10asoleus muscle10aspinal cord injury1 aChen, Xiang Yang1 aWolpaw, Jonathan1 aJakeman, L., B.1 aStokes, B., T.  uhttp://www.ncbi.nlm.nih.gov/pubmed/1009896201573nas a2200229   4500008004100000022001400041245004600055210004100101260001200142300001400154490000700168520098800175653001301163653001301176653001101189653002501200653001501225653001601240653001901256100002101275856004701296       1997                        eng d  a0166-223600aThe complex structure of a simple memory.0 acomplex structure of a simple memory  c12/1997  a588–5940 v203 aOperant conditioning of the vertebrate H-reflex, which appears to be closely related to learning that occurs in real life, is accompanied by plasticity at multiple sites. Change occurs in the firing threshold and conduction velocity of the motoneuron, in several different synaptic terminal populations on the motoneuron, and probably in interneurons as well. Change also occurs contralaterally. The corticospinal tract probably has an essential role in producing this plasticity. While certain of these changes, such as that in the firing threshold, are likely to contribute to the rewarded behavior (primary plasticity), others might preserve previously learned behaviors (compensatory plasticity), or are simply activity-driven products of change elsewhere (reactive plasticity). As these data and those from other simple vertebrate and invertebrate models indicate, a complex pattern of plasticity appears to be the necessary and inevitable outcome of even the simplest learning.10aH-Reflex10aLearning10aMemory10aoperant conditioning10aplasticity10aSpinal Cord10astretch reflex1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/941667302267nas a2200253   4500008004100000022001400041245006600055210006300121260001200184300001400196490000700210520156600217653001301783653002501796653001501821653000801836653001801844653002301862100002101885700002101906700002001927700001901947856004701966       1996                        eng d  a0897-715100aOperant conditioning of H-reflex in spinal cord-injured rats.0 aOperant conditioning of Hreflex in spinal cordinjured rats  c12/1996  a755–7660 v133 aOperant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, is a new model for exploring the mechanisms of supraspinal control over spinal cord function. Both rats and primates can gradually increase (HRup conditioning mode) or decrease (HRdown conditioning mode) soleus H-reflex magnitude when exposed to an operant conditioning task. This study used H-reflex operant conditioning to assess and modify spinal cord function after injury. Soleus H-reflexes were elicited and recorded with chronically implanted electrodes from rats that had been subjected to calibrated contusion injuries to the spinal cord at T8. From 18 to 140 days after injury, background EMG, M response amplitude, and initial H-reflex amplitude were not significantly different from those of normal rats. HRdown conditioning was successful in some, but not all, spinal cord-injured rats. The H-reflex decrease achieved by conditioning was inversely correlated with the severity of the injury as assessed histologically or by time to return of bladder function. It was not correlated with the length of time between injury and the beginning of conditioning. The results confirm the importance of descending control from supraspinal structures in mediating operantly conditioned change in H-reflex amplitude. In conjunction with recent human studies, they suggest that H-reflex conditioning could provide a sensitive new means for assessing spinal cord function after injury, and might also provide a method for initiating and guiding functional rehabilitation.10aH-Reflex10aoperant conditioning10aplasticity10arat10asoleus muscle10aspinal cord injury1 aChen, Xiang Yang1 aWolpaw, Jonathan1 aJakeman, L., B.1 aStokes, B., T.  uhttp://www.ncbi.nlm.nih.gov/pubmed/900206101790nas a2200229   4500008004100000022001400041245005800055210005600113260001200169300001200181490000800193520117500201653001301376653002501389653001501414653000801429653001801437653001601455100002101471700002101492856004701513       1996                        eng d  a0014-481900aReversal of H-reflex operant conditioning in the rat.0 aReversal of Hreflex operant conditioning in the rat  c11/1996  a58–620 v1123 aIn response to an operant conditioning task, rats can gradually increase or decrease soleus H-reflex amplitude without change in background electromyographic activity or M response amplitude. Both increase (under the HRup mode) and decrease (under the HRdown mode) develop over weeks. The present study investigated reversal of conditioned H-reflex change. Following collection of control data, rats were exposed to one mode (HRup or HRdown) for 50 days, and then exposed to the opposite mode for up to 72 days. Rats responded to each mode exposure with gradual, mode-appropriate change in H-reflex amplitude. This finding is consistent with other evidence that H-reflex conditioning depends on spinal cord plasticity. The effects of exposure to the HRup (or HRdown) mode were not affected by whether exposure followed previous exposure to the HRdown (or HRup) mode. In accord with recent studies suggesting that HRup and HRdown conditioning have different spinal mechanisms, these results suggest that reversal of H-reflex change is due primarily to the superimposition of additional plasticity rather than to decay of the plasticity responsible for the initial change.10aH-Reflex10aoperant conditioning10aplasticity10arat10asoleus muscle10aSpinal Cord1 aChen, Xiang Yang1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/895140701682nas a2200229   4500008004100000022001400041245010100055210006900156260001200225300001400237490000800251520101200259653002101271653001301292653001301305653001101318653002501329653000901354100002101363700002101384856004701405       1995                        eng d  a0304-394000aOperantly conditioned plasticity and circadian rhythm in rat H-reflex are independent phenomena.0 aOperantly conditioned plasticity and circadian rhythm in rat Hre  c08/1995  a109–1120 v1953 aRecent studies indicate that rats can increase or decrease H-reflex amplitude in response to an operant conditioning paradigm. In addition, rats also display a circadian rhythm in H-reflex amplitude. As part of the development of H-reflex conditioning in the rat as a new model for defining the plasticity underlying a simple form of learning, this study examined the relationship in the rat between operantly conditioned H-reflex change and the H-reflex circadian rhythm. When H-reflex amplitude increased or decreased in response to the operant conditioning program, its circadian rhythm showed no changes in phase and minimal change in amplitude. Furthermore, animals did not alter daily performance schedule so as to use the rhythm to increase reward probability. Thus, in the rat, H-reflex operant conditioning and the H-reflex circadian rhythm appear to be independent phenomena. The circadian rhythm should not be a significant complicating factor in studies of operantly conditioned H-reflex change.10acircadian rhythm10aH-Reflex10aLearning10aMemory10aoperant conditioning10aRats1 aChen, Xiang Yang1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/747826201137nas a2200217   4500008004100000022001400041245003800055210003600093260001200129300001400141490000800155520059500163653002100758653001900779653001300798653000800811653001100819100002100830700002100851856004700872       1994                        eng d  a0006-899300aCircadian rhythm in rat H-reflex.0 aCircadian rhythm in rat Hreflex  c06/1994  a167–1700 v6483 aWe measured soleus H-reflex in the Sprague-Dawley rat as a function of time of day. H-reflex amplitude displayed a marked diurnal variation, even though background EMG and M-response amplitude were stable through the day. The H-reflex was largest in the late morning and smallest around midnight. Thus, its rhythm was opposite in phase to the circadian rhythm found in the primate H-reflex. This rhythm is a potentially confounding factor in studies of motor function. Furthermore, its existence implies that the CNS activity underlying a specific motor performance varies with time of day.10acircadian rhythm10aelectromyogram10aH-Reflex10arat10asoleus1 aChen, Xiang Yang1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/792252002325nas a2200229   4500008004100000022001400041245009300055210006900148260001200217300001200229490000700241520165100248653001301899653001101912653002501923653001501948653001601963100002101979700002502000700002302025856004702048       1993                        eng d  a0014-481900aOperant conditioning of the primate H-reflex: factors affecting the magnitude of change.0 aOperant conditioning of the primate Hreflex factors affecting th  c12/1993  a31–390 v973 aPrimates can gradually increase or decrease H-reflex amplitude in one leg when reward depends on that amplitude. The magnitude of change varies greatly from animal to animal. This study sought to define the factors that control this magnitude. It evaluated the influence of animal age, muscle size (absolute and relative), background electromyographic activity (EMG) level, M response amplitude, initial H-reflex amplitude, performance intensity, and behavior of the contralateral leg. Fifty-four animals (Macaca nemestrina) underwent operant conditioning of the triceps surae H-reflex in one leg (the trained leg). Twenty-eight were rewarded for larger H-reflexes (HRup animals), and 26 were rewarded for smaller H-reflexes (HRdown animals). In the HRup animals, H-reflex amplitude in the trained leg rose to an average final value of 177% of its initial amplitude. Magnitude of increase varied widely across animals. Nine animals rose to 120-140%, 11 to 160-240%, three to 300% or more, and five remained within 20% of initial amplitude. In the HRdown animals, H-reflex amplitude in the trained leg decreased to an average of 69% of initial amplitude. Magnitude of decrease varied widely. Five animals decreased to 20-40%, seven to 40-60%, six to 60-80%, and eight remained within 20% of initial amplitude. Animal age, as assessed by weight, markedly affected HRdown conditioning, but not HRup conditioning. Heavy HRdown animals (> or = 6 kg) were more successful than light HRdown animals (< 6 kg). Thirteen of 14 heavy animals and only five of 12 light animals decreased to less than 80% of initial amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)10aH-Reflex10amonkey10aoperant conditioning10aplasticity10aSpinal Cord1 aWolpaw, Jonathan1 aHerchenroder, P., A.1 aCarp, Jonathan, S.  uhttp://www.ncbi.nlm.nih.gov/pubmed/813183001398nas a2200241   4500008004100000022001400041245006300055210006100118260001200179300001400191490000700205520074600212653001700958653001300975653001100988653001500999653001201014653001801026653001901044100002101063700002501084856004701109       1990                        eng d  a0165-027000aOperant conditioning of H-reflex in freely moving monkeys.0 aOperant conditioning of Hreflex in freely moving monkeys  c02/1990  a145–1520 v313 aThe H-reflex, the electrical analog of the stretch reflex or tendon jerk, is the simplest behavior of the primate CNS. It is subserved by a wholly spinal two-neuron reflex arc. Recent studies show that this reflex can be increased or decreased by operant conditioning, and that such conditioning causes plastic changes in the spinal cord itself. Thus, H-reflex conditioning provides a powerful new model for investigating primate memory traces. The key feature of this model, the conditioning task, originally required animal restraint. This report describes a new tether-based design that allows H-reflex measurement and conditioning without restraint. This design integrates the conditioning task into the life of the freely moving animal.10aconditioning10aH-Reflex10aMemory10aplasticity10aprimate10aspinal reflex10astretch reflex1 aWolpaw, Jonathan1 aHerchenroder, P., A.  uhttp://www.ncbi.nlm.nih.gov/pubmed/231981501400nas a2200253   4500008004100000022001400041245007800055210006900133260001200202300001400214490000700228520067600235653002200911653001300933653001300946653001100959653002500970653001500995653003501010653001801045100002101063700001501084856004701099       1988                        eng d  a0013-469400aOperant conditioning of primate spinal reflexes: effect on cortical SEPs.0 aOperant conditioning of primate spinal reflexes effect on cortic  c04/1988  a398–4010 v693 aPrevious studies have demonstrated operant conditioning of the primate spinal stretch reflex (SSR) and of its electrical analog, the H-reflex. We studied the evoked potential recorded over primary somatosensory cortex (SEP) which accompanies the H-reflex to determine whether the initial cortical response changes in the course of conditioned H-reflex change. When H-reflex amplitude changed, SEP amplitude also changed, but only half as much as the H-reflex. The results indicate that, while operant conditioning of the H-reflex has its largest effect on the spinal pathway of the reflex, it also has some effect on supraspinal pathways of the initial cortical response.10acortical response10aH-Reflex10aLearning10aMemory10aoperant conditioning10aplasticity10asomatosensory evoked potential10aspinal reflex1 aWolpaw, Jonathan1 aDowman, R.  uhttp://www.ncbi.nlm.nih.gov/pubmed/2450739