00805nas 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

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.

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-standing03180nas a2200277 4500008004100000022001400041245010400055210006900159260001200228300001100240490000800251520226600259653002102525653002902546653001102575653001702586653001302603653002102616653001202637653002102649653003802670100002502708700002202733700002402755856012302779 2023 eng d a1522-159800aThe human motor cortex contributes to gravity compensation to maintain posture and during reaching.0 ahuman motor cortex contributes to gravity compensation to mainta c01/2023 a83-1010 v1293 a

The neural control of posture and movement is interdependent. During voluntary movement, the neural motor command is executed by the motor cortex through the corticospinal tract and its collaterals and subcortical targets. Here we address the question of whether the control mechanism for the postural adjustments at nonmoving joints is also involved in overcoming gravity at the moving joints. We used single-pulse transcranial magnetic stimulation to measure the corticospinal excitability in humans during postural and reaching tasks. We hypothesized that the corticospinal excitability is proportional to background muscle activity and the gravity-related joint moments during both static postures and reaching movements. To test this hypothesis, we used visual targets in virtual reality to instruct five postures and three movements with or against gravity. We then measured the amplitude and gain of motor evoked potentials in multiple arm and hand muscles at several phases of the reaching motion and during static postures. The stimulation caused motor evoked potentials in all muscles that were proportional to the muscle activity. During both static postures and reaching movements, the muscle activity and the corticospinal contribution to these muscles changed in proportion with the postural moments needed to support the arm against gravity, supporting the hypothesis. Notably, these changes happened not only in antigravity muscles. Altogether, these results provide evidence that the changes in corticospinal excitability cause muscle cocontraction that modulates limb stiffness. This suggests that the motor cortex is involved in producing postural adjustments that support the arm against gravity during posture maintenance and reaching. Animal studies suggest that the corticospinal tract and its collaterals are crucial for producing postural adjustments that accompany movement in limbs other than the moving limb. Here we provide evidence for a similar control schema for both arm posture maintenance and gravity compensation during movement of the same limb. The observed interplay between the postural and movement control signals within the corticospinal tract may help explain the underlying neural motor deficits after stroke.

10aElectromyography10aEvoked Potentials, Motor10aHumans10aMotor Cortex10aMovement10aMuscle, Skeletal10aPosture10aPyramidal Tracts10aTranscranial Magnetic Stimulation1 aHardesty, Russell, L1 aEllaway, Peter, H1 aGritsenko, Valeriya uhttps://www.neurotechcenter.org/publications/2023/human-motor-cortex-contributes-gravity-compensation-maintain-posture03030nas 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

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.

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-evoked02454nas 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

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.

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-task01203nas 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/2450873802917nas 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

This report describes a temporally based method for identifying repetitive firing of motor units. This approach 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 approach 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.

10aAction Potentials10aAnimals10aElectromyography10aH-Reflex10aMotor Neurons10aMuscle, Skeletal10aRats10aSignal Processing, Computer-Assisted1 aSchalk, Gerwin1 aCarp, Jonathan, S.1 aWolpaw, Jonathan uhttp://www.ncbi.nlm.nih.gov/pubmed/11850043