The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Ole Kæseler Andersen - One of the best experts on this subject based on the ideXlab platform.
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Gait rehabilitation by nociceptive Withdrawal Reflex-based functional electrical therapy
Advanced Technologies for the Rehabilitation of Gait and Balance Disorders, 2018Co-Authors: Ole Kæseler Andersen, Erika G. SpaichAbstract:The nociceptive Withdrawal Reflex (NWR) can be used for supporting gait as the spinal stepping generator circuits can also be triggered by robust afferent input [36]. This has been utilised in many assistive functional electrical stimulation devices since the first reports by Liberson [32] who found a functional benefit when stimulating electrically the peroneal nerve during the swing phase. The NWR response is an integrated movement generated by a coordinated activation of several muscles in the limb when the body receives a potentially tissue damaging stimulus. The NWR is generated to ensure adequate and sufficient Withdrawal while maintaining balance and ensuring continuation of the ongoing motor programs [4, 41, 49]. This obviously leads to involvement of the contralateral limb to ensure upright posture and balance control. During rhythmic movements like gait, the spinal pattern generators are involved in Reflex modulation as the Reflex responses are strongly modulated by the phases of the gait cycle [17, 56].
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A Novel Stimulation Paradigm to Limit the Habituation of the Nociceptive Withdrawal Reflex
IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, 2018Co-Authors: Sabata Gervasio, Ole Kæseler Andersen, Christian B. Laursen, Kristian Hennings, Erika G. SpaichAbstract:In gait rehabilitation, combining gait therapy with functional electrical stimulation based on the nociceptive Withdrawal Reflex (NWR) improves walking velocity and gait symmetry of hemiparetic patients. However, habituation of the NWR can affect the efficacy of training. The current study aimed at identifying the stimulation parameters that would limit, in healthy participants, the habituation of the NWR. The NWR was elicited at every heel-off while the participants walked on a treadmill. Three stimulation paradigms were tested: deterministic paradigm (fixed parameters), stochastic pulse duration paradigm (varying the pulse duration of the stimuli), and stochastic frequency paradigm (varying the frequency of the stimuli). The charge delivered for the three paradigms was identical. The Reflex response was quantified by the EMG activity of the tibialis anterior (TA) muscle and as ankle and hip joints angle changes. The ankle dorsiflexion and TA EMG responses were not significantly reduced with the stochastic pulse duration paradigm, in contrast to the two other paradigms. Hence, using a stochastic pulse duration stimulation paradigm seemed to be effective in limiting the habituation of the NWR in heathy individuals. This might be highly relevant for effective gait rehabilitation.
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reliable estimation of nociceptive Withdrawal Reflex thresholds
Journal of Neuroscience Methods, 2015Co-Authors: Michael Brun Jensen, Jose Biurrun Manresa, Ole Kæseler AndersenAbstract:Abstract Background Assessment of the nociceptive Withdrawal Reflex (NWR) is frequently applied to probe the excitability level of the spinal nociceptive circuitry. In humans, the NWR threshold (NWR-T) is often estimated by applying electrical stimulation over the sural nerve at the lateral malleolus. Such stimulation may be associated with substantial pain and discomfort rendering completion of the assessment infeasible. New method As an alternative to sural nerve stimulation, NWR-Ts were also estimated by electrical stimulation at the arch of the foot. Failure-rates and test–retest reliability of these two procedures were evaluated. A fully-automated interleaved up-down staircase procedure was used to estimate the NWR-T for both stimulation sites. NWRs were detected from EMG measured over the biceps femoris and tibialis anterior muscles, respectively. A total of three repeated measures were performed in two different sessions to evaluate the test–retest reliability of the two methods using Bland–Altman agreement analysis. Results The failure rate of NWR-T estimation based on electrical stimulation of the sural nerve (29%) was substantially higher than when the NWR was elicited by stimulation at the arch of the foot (5%). Comparison with existing method The analysis of test–retest reliability indicated that the two methods for NWR-T estimation were equally reliable for within-session comparisons, but stimulation at the arch of the foot enabled NWR-T estimation with superior between-session reliability Conclusions These results support a paradigm shift within NWR-T estimation favoring stimulation at the arch of the foot.
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Reliable estimation of nociceptive Withdrawal Reflex thresholds
Journal of neuroscience methods, 2015Co-Authors: Michael Brun Jensen, Jose Biurrun Manresa, Ole Kæseler AndersenAbstract:Assessment of the nociceptive Withdrawal Reflex (NWR) is frequently applied to probe the excitability level of the spinal nociceptive circuitry. In humans, the NWR threshold (NWR-T) is often estimated by applying electrical stimulation over the sural nerve at the lateral malleolus. Such stimulation may be associated with substantial pain and discomfort rendering completion of the assessment infeasible. As an alternative to sural nerve stimulation, NWR-Ts were also estimated by electrical stimulation at the arch of the foot. Failure-rates and test-retest reliability of these two procedures were evaluated. A fully-automated interleaved up-down staircase procedure was used to estimate the NWR-T for both stimulation sites. NWRs were detected from EMG measured over the biceps femoris and tibialis anterior muscles, respectively. A total of three repeated measures were performed in two different sessions to evaluate the test-retest reliability of the two methods using Bland-Altman agreement analysis. The failure rate of NWR-T estimation based on electrical stimulation of the sural nerve (29%) was substantially higher than when the NWR was elicited by stimulation at the arch of the foot (5%). The analysis of test-retest reliability indicated that the two methods for NWR-T estimation were equally reliable for within-session comparisons, but stimulation at the arch of the foot enabled NWR-T estimation with superior between-session reliability These results support a paradigm shift within NWR-T estimation favoring stimulation at the arch of the foot. Copyright © 2015 Elsevier B.V. All rights reserved.
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Stimulation site and phase modulation of the Withdrawal Reflex during gait initiation.
Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology, 2015Co-Authors: Miguel Richard, Mariano Serrao, Erika G. Spaich, Ole Kæseler AndersenAbstract:Abstract Objective To investigate how the nociceptive Withdrawal Reflex (NWR) is modulated during gait initiation. Methods The NWR was elicited in ten subjects using electrical stimulation at four sites in the right foot during symmetrical stance (50% of body weight on each foot) or while performing the first step during gait initiation: either during heel off (HO, 20% of body load on the starting leg) or heel contact (HC, 80% of body load on the starting leg in the first step). Kinematics and EMG responses from major muscles of the ipsilateral leg were recorded. Results The NWR was modulated by stimulation site in all muscles except Soleus. The NWR responses elicited after stimulation of the arch were significantly larger than those evoked at all other sites in Tibialis Anterior, Rectus Femoris, and Vastus Lateralis. At the hip joint, the largest flexion was obtained during HO, whereas the smallest flexion was observed during HC, both following stimulation on the arch of the foot. Conclusions The NWR responses were modulated to maintain balance and continue the development of the gait initiation process. Significance The NWR modulation followed a functional principle, which might allow a functional use in rehabilitation strategies.
Erika G. Spaich - One of the best experts on this subject based on the ideXlab platform.
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Gait rehabilitation by nociceptive Withdrawal Reflex-based functional electrical therapy
Advanced Technologies for the Rehabilitation of Gait and Balance Disorders, 2018Co-Authors: Ole Kæseler Andersen, Erika G. SpaichAbstract:The nociceptive Withdrawal Reflex (NWR) can be used for supporting gait as the spinal stepping generator circuits can also be triggered by robust afferent input [36]. This has been utilised in many assistive functional electrical stimulation devices since the first reports by Liberson [32] who found a functional benefit when stimulating electrically the peroneal nerve during the swing phase. The NWR response is an integrated movement generated by a coordinated activation of several muscles in the limb when the body receives a potentially tissue damaging stimulus. The NWR is generated to ensure adequate and sufficient Withdrawal while maintaining balance and ensuring continuation of the ongoing motor programs [4, 41, 49]. This obviously leads to involvement of the contralateral limb to ensure upright posture and balance control. During rhythmic movements like gait, the spinal pattern generators are involved in Reflex modulation as the Reflex responses are strongly modulated by the phases of the gait cycle [17, 56].
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A Novel Stimulation Paradigm to Limit the Habituation of the Nociceptive Withdrawal Reflex
IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, 2018Co-Authors: Sabata Gervasio, Ole Kæseler Andersen, Christian B. Laursen, Kristian Hennings, Erika G. SpaichAbstract:In gait rehabilitation, combining gait therapy with functional electrical stimulation based on the nociceptive Withdrawal Reflex (NWR) improves walking velocity and gait symmetry of hemiparetic patients. However, habituation of the NWR can affect the efficacy of training. The current study aimed at identifying the stimulation parameters that would limit, in healthy participants, the habituation of the NWR. The NWR was elicited at every heel-off while the participants walked on a treadmill. Three stimulation paradigms were tested: deterministic paradigm (fixed parameters), stochastic pulse duration paradigm (varying the pulse duration of the stimuli), and stochastic frequency paradigm (varying the frequency of the stimuli). The charge delivered for the three paradigms was identical. The Reflex response was quantified by the EMG activity of the tibialis anterior (TA) muscle and as ankle and hip joints angle changes. The ankle dorsiflexion and TA EMG responses were not significantly reduced with the stochastic pulse duration paradigm, in contrast to the two other paradigms. Hence, using a stochastic pulse duration stimulation paradigm seemed to be effective in limiting the habituation of the NWR in heathy individuals. This might be highly relevant for effective gait rehabilitation.
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Stimulation site and phase modulation of the Withdrawal Reflex during gait initiation.
Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology, 2015Co-Authors: Miguel Richard, Mariano Serrao, Erika G. Spaich, Ole Kæseler AndersenAbstract:Abstract Objective To investigate how the nociceptive Withdrawal Reflex (NWR) is modulated during gait initiation. Methods The NWR was elicited in ten subjects using electrical stimulation at four sites in the right foot during symmetrical stance (50% of body weight on each foot) or while performing the first step during gait initiation: either during heel off (HO, 20% of body load on the starting leg) or heel contact (HC, 80% of body load on the starting leg in the first step). Kinematics and EMG responses from major muscles of the ipsilateral leg were recorded. Results The NWR was modulated by stimulation site in all muscles except Soleus. The NWR responses elicited after stimulation of the arch were significantly larger than those evoked at all other sites in Tibialis Anterior, Rectus Femoris, and Vastus Lateralis. At the hip joint, the largest flexion was obtained during HO, whereas the smallest flexion was observed during HC, both following stimulation on the arch of the foot. Conclusions The NWR responses were modulated to maintain balance and continue the development of the gait initiation process. Significance The NWR modulation followed a functional principle, which might allow a functional use in rehabilitation strategies.
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Rehabilitation of the hemiparetic gait by nociceptive Withdrawal Reflex-based functional electrical therapy: a randomized, single-blinded study
Journal of neuroengineering and rehabilitation, 2014Co-Authors: Erika G. Spaich, Niels Svaneborg, Helle Rovsing Møller Jørgensen, Ole Kæseler AndersenAbstract:Gait deficits are very common after stroke and improved therapeutic interventions are needed. The objective of this study was therefore to investigate the therapeutic use of the nociceptive Withdrawal Reflex to support gait training in the subacute post-stroke phase. Individuals were randomly allocated to a treatment group that received physiotherapy-based gait training supported by Withdrawal Reflex stimulation and a control group that received physiotherapy-based gait training alone. Electrical stimuli delivered to the arch of the foot elicited the Withdrawal Reflex at heel-off with the purpose of facilitating the initiation and execution of the swing phase. Gait was assessed before and immediately after finishing treatment, and one month and six months after finishing treatment. Assessments included the Functional Ambulation Category (FAC) test, the preferred and maximum gait velocities, the duration of the stance phase in the hemiparetic side, the duration of the gait cycle, and the stance time symmetry ratio. The treatment group showed an improved post treatment preferred walking velocity (p
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rehabilitation of the hemiparetic gait by nociceptive Withdrawal Reflex based functional electrical therapy a randomized single blinded study
Journal of Neuroengineering and Rehabilitation, 2014Co-Authors: Erika G. Spaich, Niels Svaneborg, Helle Rovsing Møller Jørgensen, Ole Kæseler AndersenAbstract:Gait deficits are very common after stroke and improved therapeutic interventions are needed. The objective of this study was therefore to investigate the therapeutic use of the nociceptive Withdrawal Reflex to support gait training in the subacute post-stroke phase. Individuals were randomly allocated to a treatment group that received physiotherapy-based gait training supported by Withdrawal Reflex stimulation and a control group that received physiotherapy-based gait training alone. Electrical stimuli delivered to the arch of the foot elicited the Withdrawal Reflex at heel-off with the purpose of facilitating the initiation and execution of the swing phase. Gait was assessed before and immediately after finishing treatment, and one month and six months after finishing treatment. Assessments included the Functional Ambulation Category (FAC) test, the preferred and maximum gait velocities, the duration of the stance phase in the hemiparetic side, the duration of the gait cycle, and the stance time symmetry ratio. The treatment group showed an improved post treatment preferred walking velocity (p < 0.001) and fast walking velocity (p < 0.001) compared to the control group. Furthermore, subjects in the treatment group with severe walking impairment at inclusion time showed the best improvement as assessed by a longer duration of the stance phase in the hemiparetic side (p < 0.002) and a shorter duration of the gait cycle (p < 0.002). The stance time symmetry ratio was significantly better for the treatment than the control group after finishing training (p < 0.02). No differences between groups were detected with the FAC test after finishing training (p = 0.09). Withdrawal Reflex-based functional electrical therapy was useful in the rehabilitation of the hemiparetic gait of severely impaired patients.
Lars Arendt-nielsen - One of the best experts on this subject based on the ideXlab platform.
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Depression of the human nociceptive Withdrawal Reflex by segmental and heterosegmental intramuscular electrical stimulation
Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology, 2007Co-Authors: Thomas Collet, Lars Arendt-nielsen, Carsten Dahl Mørch, Ole Kæseler AndersenAbstract:Abstract Objective To investigate the effects of intramuscular electrical conditioning in the modulation of nociceptive Withdrawal Reflex (NWR) and further to determine what muscle afferents are involved in the modulation of the nociceptive Withdrawal Reflex and the sites along the Reflex pathway where the NWR modulation occurs in healthy humans. Methods The NWR elicited by a cutaneous test stimulus to the dorsal foot was modulated by a short (21 ms) intramuscular conditioning electrical stimulus at two times the pain threshold. At varying conditioning–test stimulus intervals, segmental conditioning stimulus was applied in the tibialis anterior muscle ipsilateral and contralateral to the test stimulus, and heterosegmental conditioning stimulus was applied in the contralateral trapezius muscle to modulate the NWR. Non-painful and painful intramuscular conditioning stimuli were also used to modulate the NWR and the soleus H-Reflex. Results The NWR was depressed by preceding intramuscular conditioning stimuli, with a degree that depended on the conditioning–test stimulus intervals and on the conditioning site. Segmental conditioning depressed the NWR more quickly and gave a longer duration (15–1500 ms), and larger magnitude than heterosegmental conditioning, which depressed the NWR in a short temporal window (80–100 ms). No difference was seen in the magnitude of the NWR depression between the painful and non-painful intramuscular stimuli, and the soleus H-Reflex was not affected. Conclusions Our results suggest that segmental and heterosegmental conditionings of NWR are mediated by myelinated muscle afferents engaging central inhibitory mechanisms rather than direct changes in the excitability of motor neurons. Significance The therapeutic effects of electrotherapy could involve these mechanisms in the treatment of muscle pain syndromes.
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Noninvasive assessment of the facilitation of the nociceptive Withdrawal Reflex by repeated electrical stimulations in conscious dogs.
American journal of veterinary research, 2007Co-Authors: Alessandra Bergadano, Ole Kæseler Andersen, Lars Arendt-nielsen, Claudia SpadavecchiaAbstract:Objective—To investigate the facilitation of the nociceptive Withdrawal Reflex (NWR) by repeated electrical stimuli and the associated behavioral response scores in conscious, nonmedicated dogs as a measure of temporal summation and analyze the influence of stimulus intensity and frequency on temporal summation responses. Animals—8 adult Beagles. Procedures—Surface electromyographic responses evoked by transcutaneous constant-current electrical stimulation of ulnaris and digital plantar nerves were recorded from the deltoideus, cleidobrachialis, biceps femoris, and cranial tibial muscles. A repeated stimulus was given at 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, and 1.1 × It (the individual NWR threshold intensity) at 2, 5, and 20 Hz. Threshold intensity and relative amplitude and latency of the Reflex were analyzed for each stimulus configuration. Behavioral reactions were subjectively scored. Results—Repeated sub-It stimuli summated and facilitated the NWR. To elicit temporal summation, significantly lower int...
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High-frequency conditioning electrical stimulation evokes supraspinal independent long-term depression but not long-term potentiation of the spinal Withdrawal Reflex in rats.
Brain research, 2006Co-Authors: Hao-jun You, Arne Tjølsen, Lars Arendt-nielsenAbstract:The aim of the current study was to investigate the effects on the spinal Withdrawal Reflex of electrical stimulation that has been shown to induce long-term potentiation (LTP) in spinal sensory systems. This was done in order to enhance our understanding of long-term dynamic modifications of spinal motor system during the exposure to high-frequency conditioning electrical stimulation (cES). The spinal Withdrawal Reflex was assessed by extracellular recording of the single motor unit (SMU) electromyographic (EMG) activity from the medial gastrocnemius (MG) muscle in intact and acutely spinalized rats. High-frequency (1 ms pulses at 100 Hz for 2 s repeated three times at 10 s intervals) tetanic cES produced a significant long-term depression (LTD) (at least 3 h), but not LTP, of the electrically evoked SMU EMG activity as well as the wind-up phenomenon (temporal summation). There were no significant depressive or facilitatory effects of low-frequency (2 Hz) cES, consisting of the same number of pulses as the 100 Hz cES, on the SMU EMG responses. This frequency-dependent long-term depressive effect on the spinal Withdrawal Reflex was not significantly changed following acute spinalization, indicating that LTD of the spinal motor system elicited by high-frequency cES is independent of the descending control system. We conclude that, in contrast to LTP in spinal sensory systems to brief tetanic C-fiber cES, high-frequency cES seems only to elicit LTD of motor systems of the spinal cord.
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Repetitive painful stimulation produces an expansion of Withdrawal Reflex receptive fields in humans.
Artificial organs, 2005Co-Authors: Erika G. Spaich, Lars Arendt-nielsen, Ole Kæseler AndersenAbstract:The aims of the present study were to investigate whether temporal summation of the nociceptive Withdrawal Reflex depends on the stimulation site on the sole of the human foot, and to characterize the Reflex receptive fields (RRF) of lower limb muscles to repetitive stimulation. The cutaneous RRFs were assessed in 15 subjects in sitting position by recording the EMG from five lower leg muscles and the kinematic responses (ankle, knee, and hip joints) to repetitive painful electrical stimulation. The stimulus consisted of a series of five stimuli (frequency: 3 Hz) delivered randomly at 10 different sites on the sole of the foot. The size of the Reflexes increased generally between the first and the second stimulus, however, the increment depended on the stimulation site. In tibialis anterior, the RRF covered the distal sole of the foot and gradually expanded during the stimulus train. No expansion toward the heel area was detected. In soleus, the Reflexes were facilitated after the second stimulus at all sites and remained in this state until the last stimulus. In vastus lateralis, biceps femoris, and iliopsoas a gradual expansion of the RRF was seen, resulting in RRFs covering the lateral, distal foot, and part of the proximal foot (iliopsoas). Knee and hip flexion were evoked at all sites. Ankle dorsiflexion was evoked at the distal foot, while ankle plantarflexion was evoked at the heel. The enlargement of the RRF reflects spinal temporal summation leading to gradually stronger Reflex responses. The degree of temporal summation was dependent on stimulation site. The facilitation of the Withdrawal Reflex responses due to repetitive stimulation might have potential applications in the rehabilitation engineering field, where these Reflexes could be used to assist gait of patients with central nervous system injuries.
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Electrophysiological characterization of facilitated spinal Withdrawal Reflex to repetitive electrical stimuli and its modulation by central glutamate receptor in spinal anesthetized rats.
Brain research, 2004Co-Authors: Hao-jun You, Carsten Dahl Mørch, Lars Arendt-nielsenAbstract:The present study is aimed to systematically investigate wind-up and after-discharge of the spinal Withdrawal Reflex assessed by recording single motor unit (SMU) electromyographic (EMG) response to different intensities [0.5-1.5xReflex threshold (T)] of repetitive [frequencies (0.5-200 Hz)] transcutaneous electrical stimuli for 5 s. The role of central glutamate receptors in modulation of the Withdrawal Reflex facilitation was observed and evaluated in order to explore the potential central mechanism. Stimulus intensities below Reflex threshold, such as 0.8xT, but not 0.5xT, could by repetition elicit and facilitate Withdrawal Reflex. The facilitation (wind-up and after-discharge) of the Withdrawal Reflex is a result of central integration and is increased significantly for increasing stimulus intensity and frequency. Electrical stimuli at 3-5 Hz for 5 s are appropriate to elicit wind-up. In contrast, 10-20 Hz frequencies of electrical stimuli are adequate to evoke the after-discharge. For pharmacological intervention, suprathreshold (1.5xT) repeated (5 Hz) electrically evoked facilitated Reflex (wind-up) were apparently depressed by intrathecal (i.t.) administration of MK-801 as well as CNQX (40 nmol/10 microl, respectively). However, wind-up of spinal Reflexes evoked by subthreshold (0.8xT) electrical stimuli could only be depressed by the treatment with CNQX, not MK-801. The after-discharge of the Withdrawal Reflex elicited by 20 Hz electrical stimulation with either 0.8xT or 1.5xT intensity was depressed by i.t. treatment with CNQX. I.t. application of MK-801 only depressed 0.8xT the intensity of electrically evoked after-discharge. In conclusion, for the first time, the present study clearly demonstrates that, following the wind-up phase, the spinal Withdrawal Reflex pathways continue to fire spontaneously in a stimulus frequency- and intensity-dependent way (temporal and/or spatial summation). This inherited memory and the central non-N-methyl-d-aspartate (non-NMDA) receptor, but not the NMDA receptor, mainly involving pharmacological mechanisms, may play an important role in pathological conditions with spontaneous nociceptive firing. Furthermore, the after-discharge of the spinal Reflex may be an important indicator for studies on central sensitization in many pathological pain conditions.
Hao-jun You - One of the best experts on this subject based on the ideXlab platform.
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High-frequency conditioning electrical stimulation evokes supraspinal independent long-term depression but not long-term potentiation of the spinal Withdrawal Reflex in rats.
Brain research, 2006Co-Authors: Hao-jun You, Arne Tjølsen, Lars Arendt-nielsenAbstract:The aim of the current study was to investigate the effects on the spinal Withdrawal Reflex of electrical stimulation that has been shown to induce long-term potentiation (LTP) in spinal sensory systems. This was done in order to enhance our understanding of long-term dynamic modifications of spinal motor system during the exposure to high-frequency conditioning electrical stimulation (cES). The spinal Withdrawal Reflex was assessed by extracellular recording of the single motor unit (SMU) electromyographic (EMG) activity from the medial gastrocnemius (MG) muscle in intact and acutely spinalized rats. High-frequency (1 ms pulses at 100 Hz for 2 s repeated three times at 10 s intervals) tetanic cES produced a significant long-term depression (LTD) (at least 3 h), but not LTP, of the electrically evoked SMU EMG activity as well as the wind-up phenomenon (temporal summation). There were no significant depressive or facilitatory effects of low-frequency (2 Hz) cES, consisting of the same number of pulses as the 100 Hz cES, on the SMU EMG responses. This frequency-dependent long-term depressive effect on the spinal Withdrawal Reflex was not significantly changed following acute spinalization, indicating that LTD of the spinal motor system elicited by high-frequency cES is independent of the descending control system. We conclude that, in contrast to LTP in spinal sensory systems to brief tetanic C-fiber cES, high-frequency cES seems only to elicit LTD of motor systems of the spinal cord.
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Electrophysiological characterization of facilitated spinal Withdrawal Reflex to repetitive electrical stimuli and its modulation by central glutamate receptor in spinal anesthetized rats.
Brain research, 2004Co-Authors: Hao-jun You, Carsten Dahl Mørch, Lars Arendt-nielsenAbstract:The present study is aimed to systematically investigate wind-up and after-discharge of the spinal Withdrawal Reflex assessed by recording single motor unit (SMU) electromyographic (EMG) response to different intensities [0.5-1.5xReflex threshold (T)] of repetitive [frequencies (0.5-200 Hz)] transcutaneous electrical stimuli for 5 s. The role of central glutamate receptors in modulation of the Withdrawal Reflex facilitation was observed and evaluated in order to explore the potential central mechanism. Stimulus intensities below Reflex threshold, such as 0.8xT, but not 0.5xT, could by repetition elicit and facilitate Withdrawal Reflex. The facilitation (wind-up and after-discharge) of the Withdrawal Reflex is a result of central integration and is increased significantly for increasing stimulus intensity and frequency. Electrical stimuli at 3-5 Hz for 5 s are appropriate to elicit wind-up. In contrast, 10-20 Hz frequencies of electrical stimuli are adequate to evoke the after-discharge. For pharmacological intervention, suprathreshold (1.5xT) repeated (5 Hz) electrically evoked facilitated Reflex (wind-up) were apparently depressed by intrathecal (i.t.) administration of MK-801 as well as CNQX (40 nmol/10 microl, respectively). However, wind-up of spinal Reflexes evoked by subthreshold (0.8xT) electrical stimuli could only be depressed by the treatment with CNQX, not MK-801. The after-discharge of the Withdrawal Reflex elicited by 20 Hz electrical stimulation with either 0.8xT or 1.5xT intensity was depressed by i.t. treatment with CNQX. I.t. application of MK-801 only depressed 0.8xT the intensity of electrically evoked after-discharge. In conclusion, for the first time, the present study clearly demonstrates that, following the wind-up phase, the spinal Withdrawal Reflex pathways continue to fire spontaneously in a stimulus frequency- and intensity-dependent way (temporal and/or spatial summation). This inherited memory and the central non-N-methyl-d-aspartate (non-NMDA) receptor, but not the NMDA receptor, mainly involving pharmacological mechanisms, may play an important role in pathological conditions with spontaneous nociceptive firing. Furthermore, the after-discharge of the spinal Reflex may be an important indicator for studies on central sensitization in many pathological pain conditions.
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role of central nmda versus non nmda receptor in spinal Withdrawal Reflex in spinal anesthetized rats under normal and hyperexcitable conditions
Brain Research, 2003Co-Authors: Hao-jun You, Carsten Dahl Mørch, Jun Chen, Lars ArendtnielsenAbstract:Abstract The present study aimed to investigate the role of central N-methyl- d -aspartate (NMDA) and non-NMDA receptors in the spinal Withdrawal Reflex assessed by recording single motor unit (SMU) electromyogram (EMG) response to peripheral mechanical (pressure, pinch) stimuli and repeated electrical stimuli at 3 and 20 Hz. During normal conditions, intrathecal administration of MK-801 and CNQX apparently depressed mechanically and electrically (3 Hz) evoked EMG responses in a dose-dependent manner (10, 20 and 40 nmol in 10 μl). In contrast, the after-discharges to 20 Hz electrical stimuli were suppressed only by CNQX treatment, not by MK-801 treatment. This indicates that the central mechanisms underlying the different frequencies of electrically evoked Withdrawal Reflex may be different. During peripheral bee venom (BV, 0.2 mg/50 μl) induced inflammation and central sensitization, the enhanced SMU EMG responses including after-discharges to pinch stimuli and 3 Hz electrical stimuli were depressed significantly by treatments with both MK-801 and CNQX. However, the enhanced SMU activities to innocuous pressure stimuli were depressed only by treatment with CNQX. Likewise, enhanced long lasting after-discharges elicited by 20 Hz electrical stimuli were also only depressed by CNQX, indicating that different central mechanisms are involved in the persistent hyperexcitability during BV-induced inflammation. The data suggest that both central NMDA and non-NMDA receptors play important roles in the transmission of nociceptive information under normal conditions. In BV-induced inflammation, however, central non-NMDA receptors, but not NMDA receptors, play a pivotal role in the generation of persistent hyperexcitability to mechanical and electrical stimuli at different frequencies (3 Hz, 20 Hz).
Jens Schouenborg - One of the best experts on this subject based on the ideXlab platform.
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Sensorimotor transformation in cat nociceptive Withdrawal Reflex system.
The European journal of neuroscience, 1999Co-Authors: Anders Levinsson, Martin Garwicz, Jens SchouenborgAbstract:The Withdrawal Reflex system of higher vertebrates has been extensively used as a model for spinal sensorimotor integration, nociceptive processing and plasticity. In the rat, the nociceptive Withdrawal Reflex system appears to have a modular organization. Each Reflex module controls a single muscle or a few synergistic muscles, and its cutaneous receptive field corresponds to the skin area withdrawn upon contraction of the effector muscle(s) when the limb is in the standing position. This organization principle is at odds with the 'flexion Reflex' concept postulated from cat studies. To assess the generality of the modular organization principle we have therefore re-examined the cutaneous input to the Withdrawal Reflex system of the cat. The cutaneous receptive fields of hindlimb and forelimb muscles were mapped using calibrated noxious pinch stimulation and electromyographic recording technique in barbiturate anaesthetized animals. The investigated muscles had specific cutaneous receptive fields that appeared to correspond to the area of the skin withdrawn upon contraction of the muscle when the limb is in the standing position. The spatial organization of receptive fields in the cat was similar to that in the rat. However, differences in gain properties of Reflexes to some anatomically equivalent muscles in the two species were observed, possibly reflecting adaptations to the biomechanics characteristic of the digitigrade and plantigrade stance in cats and rats, respectively. Implications of the findings for the generality of the modular organization of the Withdrawal Reflex system and for its adaptive properties are discussed.
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On the cutaneous receptors contributing to Withdrawal Reflex pathways in the decerebrate spinal rat.
Experimental brain research, 1998Co-Authors: Han-rong Weng, Jens SchouenborgAbstract:Previous studies indicate that the Withdrawal Reflex system in the rat has a “modular” organization, each Reflex pathway performing a specific sensorimotor transformation. Here, we wished to clarify which cutaneous receptors contribute to this system and to determine whether there are differences in this respect between Reflex pathways of different muscles. Withdrawal Reflexes of the peroneus longus, extensor digitorum longus, and semitendinosus muscles were recorded with EMG techniques during high Reflex excitability in decerebrate spinal rats (n=26). While maintained innocuous pressure on glabrous skin could elicit a sustained Reflex activity in all muscles studied, vibration of glabrous skin (10–300 Hz) always failed to evoke a Reflex response, suggesting that slowly adapting, but not rapidly adapting, low-threshold mechanoreceptive fibers from this type of skin contribute to Withdrawal Reflex pathways. Thermal stimulation in the innocuous range, i.e., cooling from 32 to 17°C, or warming the skin from 32 to 41°C, always failed to produce Reflex responses, indicating that neither cold nor warm receptors contribute to Withdrawal Reflex pathways. When either cooling or warming the skin to the noxious temperatures of 1°C or above 45°C, respectively, a Reflex discharge was often evoked in the muscles studied. Intradermal administration of histamine, a potent pruritogenic substance, produced very weak, or no, Reflex response. In contrast, mustard oil produced vigorous Reflex responses in all muscles studied. These findings suggest that some chemonociceptors contribute only weakly, or not at all, to Withdrawal Reflex pathways. The present data suggest that a selective set of cutaneous receptors contribute to Withdrawal Reflex pathways and that different Withdrawal Reflex pathways receive input from essentially the same cutaneous receptor types.
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Nociceptive inhibition of Withdrawal Reflex responses increases over time in spinalized rats
Neuroreport, 1996Co-Authors: Han-rong Weng, Jens SchouenborgAbstract:Time-dependent changes of nociceptive inhibition of hindlimb Withdrawal Reflex (WR) pathways were investigated in acute decerebrate spinal rats. Electromyographic recordings of WR of peroneus longus and extensor digitorum longus muscles were made. For each muscle, both short and long latency WR evoked by subcutaneous electrical stimulation and WR evoked by noxious pinch could be inhibited by noxious CO2 laser stimulation of a specific skin area of the ipsilateral hindlimb. The inhibitory effects and size of the inhibitory receptive fields increased spontaneously between two- and three- fold during the first 12 h after spinalization. The functional and possible clinical significance of the strengthened nociceptive inhibitory control and mechanisms underlying the changes of this control after spinal transection are discussed. (Less)
