Rhythmic Muscle Activity Research Articles

Comparison of rhythmic jaw muscle activities induced by electrical stimulations of the corticobulbar tract during rapid eye movement sleep with those during wakefulness and non-rapid eye movement sleep in freely moving Guinea pigs

ObjectiveRhythmic jaw muscle activities (RJMAs) occur during rapid eye movement (REM) sleep in humans and animals even though motoneurons are inhibited. The present study compared the characteristics of jaw muscle activities induced by electrical microstimulations of the corticobulbar tract (CT) during REM sleep with those during wakefulness and non-REM sleep. MethodsEleven guinea pigs were surgically prepared for polygraphic recordings with the implantation of a stimulating electrode. Long- and short-train repetitive electrical microstimulations were applied to the CT under freely moving conditions. The response rate, latency, burst amplitude, and cycle length in the digastric muscle were calculated and cortical and cardiac activities were quantified. ResultsLong-train microstimulations induced RJMAs in the digastric muscle followed by masseter muscle activity during wakefulness and non-REM sleep and only induced rhythmic digastric muscle activity during REM sleep. The response rate of RJMAs and the burst amplitude of digastric muscles were significantly lower during REM sleep than during wakefulness and non-REM sleep. However, response latency did not significantly differ between REM sleep and wakefulness. Transient cortical and cardiac changes were associated with RJMAs induced during non-REM sleep, but not during REM sleep. Short-train microstimulations induced a short-latency digastric response, the amplitude of which was significantly lower during REM sleep than during non-REM sleep and wakefulness. ConclusionsThese results suggest that the masticatory CPG was activated by electrical CT stimulations independently of the motoneuron inhibitory system during REM sleep.

Cognitive interference of respiratory versus limb muscle dual tasking in healthy adults.

Inspiratory threshold loading (ITL) and associated dyspnoea have been shown to interfere with cognition during cognitive-motor dual tasking. However, ITL has not been compared with another rhythmic muscle activity, such as lower limb pedalling. While ITL has been shown to interfere with cognition, the mechanism of the prefrontal cortex (PFC) during ITL or other rhythmical muscle dual tasking, has not been elucidated. Given the cognitive interference that arises during ITL, we hypothesise that ITL cognitive-motor dual tasking will result in greater cognitive decrements and increased PFC activity compared with the pedalling cognitive-motor dual task. 30 healthy participants (16 females; median age 23 (interquartile range 23-24) years) were recruited. They performed five 3-min tasks in a single visit in a random order: single tasks were ITL, pedalling and Stroop task and dual tasks were ITL-Stroop and pedalling-Stroop. Participant's PFC activity was assessed bilaterally using functional near-infrared spectroscopy throughout each task. Single- and dual-task cognitive performance was evaluated by measuring Stroop task reaction time and accuracy. Dyspnoea and rating of perceived exertion were evaluated at the end of each task. ITL-Stroop resulted in greater impairments in reaction time (p<0.001), accuracy (p<0.01) and increased medial/dorsolateral PFC activity (p≤0.006) than pedalling-Stroop. ITL-Stroop elicited greater Borg dyspnoea and rating of perceived exertion than pedalling-Stroop (p<0.001), despite pedalling-Stroop having a greater heart rate response (p<0.001). The heightened cognitive decrements, perceptual response and PFC activity suggest that inspiratory muscle loading and its accompanied dyspnoea results in greater cognitive interference than rhythmic pedalling.

Poster (Knowledge Generation) ID 1985240

Background Following a spinal cord injury, there is a significant loss of monoamines below the lesion. In the rat model, exogenous administration of the serotonin precursor, 5-hydroxytryptophan (5HTP), increases neural excitability through augmentation of spinal serotonin levels. To determine whether this compensatory mechanism can be harnessed to restore serotonergic modulation in humans after SCI, participants visited the lab on four occasions where they received i) placebo, ii) carbidopa, iii) 50mg 5HTP+carbidopa, or iv) 100mg 5HTP+carbidopa in a randomized, crossover design. Cutaneomuscular reflexes (CMR) were obtained pre-drug and 30, 60, 90 and 120-min post-drug intake. Surface electromyography was also recorded during a pedalling movement pre- and post-drug. Results Nine participants with chronic, complete SCI (35.3±5.5 years) and four participants with chronic, incomplete SCI (47.0±19.7years) were enrolled. Following ingestion of 100mg 5HTP only, the short polysynaptic and long-lasting reflex components of the CMR were significantly increased by ∼ 86±61% and 58±17% respectively in individuals with complete SCI. No significant changes were noted in the cohort of individuals with incomplete SCI. Integrated EMG during pedalling was increased in multiple lower extremity muscles during the extension and flexion phases of the cycle following both 50-mg (82±15% and 51±7%) and 100-mg 5HTP (140±27% and 130±16%) in individuals with more severe injuries, but not in those with incomplete injuries. Conclusion Ingestion of 5HTP facilitates neural excitability and induces rhythmic muscle activity in previously inactive muscles during an assisted pedalling movement in individuals with chronic, complete SCI. This has significant clinical implications for rehabilitation after SCI.

Systematic Review on the Link between Sleep Bruxism and Systemic Chronic Inflammation.

Sleep bruxism (SB) is a sleep-related behavior characterized as rhythmic (phasic) or non-rhythmic (tonic) masticatory muscle activity. SB is a common sleep behavior with a predominantly central origin. The aim of this systematic review was to evaluate the relationship between inflammatory status and SB according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA 2020). The research was registered at PROSPERO (CRD42023395985). We performed a systematic literature analysis using five different databases. Furthermore, the backward snowballing technique was applied to identify additional papers. Initially, 28 papers were screened from the database search, and 162 papers were revealed in the backward snowballing process. Eventually, five articles were included. Data concerning the inflammatory status of patients experiencing SB were investigated and summarized. Due to the heterogeneity of the compared studies, only a qualitative comparison and narrative summary were performed. The results suggest that SB could be associated with systemic inflammation. In fact, this systematic review revealed that there are no papers conclusively showing that the inflammatory status in bruxers is comparable to non-bruxers. However, each of the examined studies utilized different methods of assessing systemic inflammation, which makes the results dubious.

Longitudinal electromyographic analysis of jaw-closing muscle activities during ingestive behaviors from pre-weaning to juvenile periods in rats

This longitudinal study investigated developmental changes in jaw-closing muscle activities during ingestive behaviors in rats.On postnatal day (P) 10, electromyography (EMG) electrodes were inserted into the masseter and temporalis muscles of rat pups. EMG activities were recorded for the following ingestive behaviors between P14 and P49: for suckling, including nipple attachment and rhythmic sucking on P14 and for pasta biting, pellet chewing, and milk licking between P21 and P49. Burst rhythms and muscle coordination (i.e., the correlation and time lag) between masseter and temporalis activities were assessed for each behavior.The burst rhythms of nipple attachment and rhythmic sucking on P14 were significantly slower than those of pasta biting, pellet chewing, and milk licking on P21. Muscle coordination differed between suckling on P14 and mastication and licking on P21. Between P21 and P49, increases were observed in burst rhythms for pasta biting and pellet chewing. The rate of increases in burst rhythms was higher for pasta biting than for pellet chewing. Muscle coordination between the two muscle activities for pasta biting did not significantly change between P21 and P49, whereas that for pellet chewing significantly changed between P21 and P24 and stabilized after P24. Burst rhythms for milk licking did not significantly change over time, while muscle coordination between the two muscle activities changed from agonist to antagonist muscle-like activity on approximately P35.The present results demonstrate that distinct patterns of rhythmic jaw-closing muscle activities emerge before weaning, they continue to change over time, and they exhibit unique developmental dynamics for each behavior after weaning.

The depth of anesthesia under sevoflurane can be monitored based on calling names language paradigm and Ag/AgCl electrooculogram electrode

In the depth of anesthesia monitoring, electrooculogram is usually treated as an artifact of EEG. However, the amplitude of the electrooculogram is much greater than that of electroencephalography. Its requirements for electrode materials and detection circuits are also far lower than electroencephalography. In this prospective cohort study, we use a new language paradigm that elicited rhythmic ocular muscle activity to explore whether the electrooculogram can be used for monitoring the depth of anesthesia. Thirty-three patients inhaled sevoflurane via a laryngeal mask for induction of anesthesia. According to the end-tidal sevoflurane concentration, patients were studied under three depth of sedation. Throughout all periods, the rhythmic calling of the patient’s own name script was sporadically played at a frequency of 0.5 Hz. We found that the electrooculogram was synchronized to the language paradigm during induction with sevoflurane, and the Ag/AgCl electrode has a significantly higher signal-to-noise ratio and 0.5 hz spectral peak value than other electrode. With the increase in the sevoflurane concentration, the synchronizing ability gradually weakened and eventually disappeared. Based on this evidence, we proposed a new method that can improve the performance of the anesthesia prediction monitoring model.

Robotic Exoskeleton Gait Training in Stroke: An Electromyography-Based Evaluation.

The recovery of symmetric and efficient walking is one of the key goals of a rehabilitation program in patients with stroke. The use of overground exoskeletons alongside conventional gait training might help foster rhythmic muscle activation in the gait cycle toward a more efficient gait. About twenty-nine patients with subacute stroke have been recruited and underwent either conventional gait training or experimental training, including overground gait training using a wearable powered exoskeleton alongside conventional therapy. Before and after the rehabilitation treatment, we assessed: (i) gait functionality by means of clinical scales combined to obtain a Capacity Score, and (ii) gait neuromuscular lower limbs pattern using superficial EMG signals. Both groups improved their ability to walk in terms of functional gait, as detected by the Capacity Score. However, only the group treated with the robotic exoskeleton regained a controlled rhythmic neuromuscular pattern in the proximal lower limb muscles, as observed by the muscular activation analysis. Coherence analysis suggested that the control group (CG) improvement was mediated mainly by spinal cord control, while experimental group improvements were mediated by cortical-driven control. In subacute stroke patients, we hypothesize that exoskeleton multijoint powered fine control overground gait training, alongside conventional care, may lead to a more fine-tuned and efficient gait pattern.

Temporomandibular disorders in patients with polysomnographic diagnosis of sleep bruxism: a case–control study

Temporomandibular disorders (TMD) is a collective term that refers to complaints of temporomandibular joint (TMJ) pain, fatigue and/or pain of the craniocervical muscles, limitation of movement of the mandible, and TMJ noises. Sleep bruxism (SB) is a disorder involving rhythmic (phasic) or non-rhythmic (tonic) masticatory muscle activity during sleep and is not a movement disorder or a sleep disorder in otherwise healthy individuals. The present study aimed to support or reject the null hypothesis that there is no association between SB and TMD. The study population was recruited from patients who visited the Artmedica Clinic, Mossoro city, Rio Grande do Norte, Brazil. Patients who underwent polysomnography received information about the research and were invited to participate following the inclusion and exclusion criteria. The study sample consisted of 40 individuals with age ranging from 19 to 76years. The subjects were administered the questionnaire of the European Academy of Craniomandibular Disorders (AEDC). Those who answered affirmatively to at least one question of the questionnaire were recommended to visit the primary researcher's dental clinic for examination; those who met the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) were evaluated, and their condition was classified into one or more subtypes of TMD. The subjects were divided into 4 groups according to the polysomnographic findings and the responses to the AEDC questionnaire. Of the 40 individuals who answered the AEDC questionnaire and underwent polysomnography, 28 presented with TMD symptoms. The data were expressed as simple frequency and percentage values using statistical software. Values of p < 0.05 were considered to be significant. The results showed that the frequency of TMD in individuals diagnosed to have SB was 46.4%. According to the DC/TMD of the 28 individuals, the most prevalent TMD subtype was local myalgia (85.7%). Of the total subjects, 32.5% had TMD and SB, 36.4% were males,and in the age range of 31 to 40years (40%). In this study sample, there was no association between SB as currently defined and TMD, thus confirming previous findings on this topic.

Acute intrathecal BDNF enhances functional recovery after cervical spinal cord injury in rats.

Unilateral C2 hemisection (C2SH) disrupts descending inspiratory-related drive to phrenic motor neurons and thus, silences rhythmic diaphragm muscle (DIAm) activity. There is gradual recovery of rhythmic DIAm EMG activity over time post-C2SH, consistent with neuroplasticity, which is enhanced by chronic (2 wk) intrathecal BDNF treatment. In the present study, we hypothesized that acute (30 min) intrathecal BDNF treatment also enhances recovery of DIAm EMG activity after C2SH. Rats were implanted with bilateral DIAm EMG electrodes to verify the absence of ipsilateral eupneic DIAm EMG activity at the time of C2SH and at 3 days post-C2SH. In those animals displaying no recovery of DIAm EMG activity after 28 days (n = 7), BDNF was administered intrathecally (450 mcg) at C4. DIAm EMG activity was measured continuously both before and for 30 min after BDNF treatment, during eupnea, hypoxia-hypercapnia, and spontaneous sighs. Acute BDNF treatment restored eupneic DIAm EMG activity in all treated animals to an amplitude that was 78% ± 9% of pre-C2SH root mean square (RMS) (P < 0.001). In addition, acute BDNF treatment increased DIAm RMS EMG amplitude during hypoxia-hypercapnia (P = 0.023) but had no effect on RMS EMG amplitude during sighs. These results support an acute modulatory role of BDNF signaling on excitatory synaptic transmission at phrenic motor neurons after cervical spinal cord injury.NEW & NOTEWORTHY Brain-derived neurotrophic factor (BDNF) plays an important role in promoting neuroplasticity following unilateral C2 spinal hemisection (C2SH). BDNF was administered intrathecally in rats displaying lack of ipsilateral inspiratory-related diaphragm (DIAm) EMG activity after C2SH. Acute BDNF treatment (30 min) restored eupneic DIAm EMG activity in all treated animals to 78% ± 9% of pre-C2SH level. In addition, acute BDNF treatment increased DIAm EMG amplitude during hypoxia-hypercapnia but had no effect on EMG amplitude during sighs.

Hypothermia induces opposite response in vascular and non-vascular smooth muscles.

The mechanism of cooling-induced response of smooth muscles remains little understood despite the increasing importance given to it in recent years. The aim of this study was to examine the possibility of releasing a relaxant or a contractile substance during cooling from vascular and non-vascular smooth muscles. Assessing the effect of cooling for two different smooth muscles together, vascular (aorta or carotid) which induced relaxation, and non-vascular (jejunum or bladder) which induced contraction. Hanging a pair of smooth muscle strips from different body organs in the same organ bath filled with Krebs solution, each strip was connected to its own transducer and recorder and stepwise cooling was applied. Recordings of isometric tension using organ-bath techniques. Step-wise cooling (37°C-4°C) of aorta and carotid smooth muscle preparations induced reproducible graded relaxation while jejunum and bladder preparations induced reproducible graded tonic contractions, inversely proportional to temperature. The responses of all the smooth muscle preparations were the same magnitude either alone or as a pair in the organ bath. Cooling abolished rhythmic smooth muscle activity of jejunum and bladder. Cooling-induced contraction was reduced by incubation in Ca2+-free solution. The effect of cooling either relaxation or contraction was not enhanced or attenuated by the presence of the two different smooth muscles with opposite response in the same organ bath, proving the absence of a relaxant or a contractile substance released during cooling. Cooling of aorta and carotid artery induced relaxation while jejunum and bladder induced contraction. The response to cooling is inversely proportional to the temperature. There was neither a relaxant nor a contractile substance released from vascular or non-vascular smooth muscles during cooling. Our study suggested that the effect of cooling is through a thermal receptor with two subtype one in the vascular smooth muscle (deep blood vessels) which induces relaxation, and the second in non-vascular smooth muscles (non-vascular organs) that induces contraction and the responses depend on extracellular calcium.

Evaluation of Rhythmic Masseter Muscle Activity during Sleep and Awake in Patients with Dentofacial Deformity.

Investigate the activity of rhythmic masseter muscles activity (RMMA) during sleep in patients with dentofacial deformities. Fifty patients with dentofacial deformities (16 male, 34 female) who required orthognathic surgery. An electrode was attached to the masseter muscle bilaterally, and preoperative polysomnography was performed. The frequency of RMMA onset per hour was measured on the left and the right sides. Values were classified as phasic (grinding: P-RMMA) and tonic (clenching: T-RMMA) to examine the onset of RMMA. Correlation between the RMMA index and various morphological and physical factors were determined including sleep or awake, rapid eye movement (REM), non-rapid eye movement (NREM) phases (NR1-NR4) in the sleep stage, phasic and tonic, gender, and mandibular asymmetry. The RMMA index values at the time of sleep were significantly small than during awake. The values were significantly higher during the NREM sleep than during the REM sleep and were the highest in the NR1 phase. P-RMMA index was significantly higher than the T-RMMA index. The P-RMMA index was also significantly higher than the T-RMMA index for men. In patients with greater asymmetry in the RMMA index values between the left and the right side (more than 30% difference), deviation between the midpoint of the maxillary and the mandibular incisal edges (U1-L1 deviation) was significantly higher. RMMA in patients with dentofacial deformity was statistically higher in awake than sleep, higher in NREM sleep than REM sleep, higher in male than female on grinding, and higher in upper and lower incisor high deviation.

A Robotic Gait Training System with Stair-climbing Mode Based on a Unique Exoskeleton Structure with Active Foot Plates

This paper introduces a newly developed robotic gait training system for lower-limb rehabilitation of stroke patients. The system (Cyborg-Trainer L; Cyborg-Lab Co., Korea) provides a stair-climbing mode in addition to the conventional level-walking mode by leveraging a unique exoskeleton structure with separately operable foot plates. Unlike conventional end-effector type gait training robots, the subject’s feet are not constrained by foot plates, but are free to emulate the ground or a set of stairs. The ground reaction force is measured by force sensors in the foot plates and utilized to compensate for the vertical movement of pelvis. The exoskeleton structures are connected at hip, knee, and ankle joints, and these can support a patient’s weight to ensure a normal gait pattern. The system has four control modes with different levels of assistive or resistance force. To show the feasibility of the developed training mode, a series of experiments measuring muscle activity were conducted during 1) level-walking with the robot, 2) level-walking on a treadmill without a robot, 3) stair-climbing with the robot, and 4) actual stairclimbing without a robot. The muscle activation from the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius medialis of the dominant leg of five healthy adults were measured and analyzed. Results showed that all muscles had a rhythmic muscle activation pattern. Even though muscle activation patterns were different between gaits using the robotic gait system and those not using it, reduced amplitudes and phasic muscle activations were observed during the training in the robotic system. The developed system is a new type of robotic gait training system that could induce phasic lower limb muscle activation patterns, and its clinical efficacy will be validated in clinical trials after regulatory approval.

Fatigue-independent alterations in muscle activation and effort perception during forearm exercise: role of local oxygen delivery.

The oxygen-conforming response (OCR) of skeletal muscle refers to a downregulation of muscle force for a given muscle activation when oxygen delivery (O2D) is reduced, which is rapidly reversed when O2D is restored. We tested the hypothesis that the OCR exists in voluntary human exercise and results in compensatory changes in muscle activation to maintain force output, thereby altering perception of effort. In eight men and eight women, electromyography (EMG), oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb), forearm blood flow (FBF), and task effort awareness (TEA) were measured. Participants completed two nonfatiguing rhythmic handgrip tests consisting of 5-min steady state (SS) followed by two bouts of 2-min brachial artery compression to reduce FBF by ~50% of SS (C1 and C2), separated by 2 min of no compression (NC1) and ending with 2 min of no compression (NC2). When FBF was compromised during C1, EMG/Force (1.58 ± 0.39) increased compared with SS (1.31 ± 0.33, P = 0.001). However, EMG/Force was not restored upon FBF restoration at NC1 (1.48 ± 0.38, P = 0.479), consistent with C1 evoking skeletal muscle fatigue. When FBF was compromised during C2, EMG/Force increased (1.73 ± 0.50) compared with NC1 (1.48 ± 0.38, P = 0.013). EMG/Force returned to NC1 levels during NC2 (1.50 ± 0.39, P = 0.016), consistent with an OCR in C2. TEA (SS 2.2 ± 2.3, C1 3.9 ± 2.5, NC1 3.4 ± 2.7, C2 4.6 ± 2.7, NC2 3.9 ± 2.8) mirrored changes in EMG. It is noteworthy that during the second compromise and then restoration of muscle oxygenation EMG and TEA were rapidly restored to precompromise levels. We interpreted these findings to support the existence of an OCR and its ability to rapidly modify perception of effort during voluntary exercise. NEW & NOTEWORTHY In healthy individuals, when force output is maintained during rhythmic handgrip exercise, muscle activation and perception of effort rapidly increase with compromised muscle oxygen delivery (O2D) and then return to precompromised levels when muscle O2D is restored. These findings suggest that an oxygen-conforming response (OCR) exists and is able to modify perception of effort during voluntary exercise. Therefore, similar to fatigue, an OCR may have implications for exercise tolerance.

Synergistic influences of sensory and central stimuli on non-voluntary rhythmic arm movements

In recent years, neuromodulation of the cervical spinal circuitry has become an area of interest for investigating rhythmogenesis of the human spinal cord and interaction between cervical and lumbosacral circuitries, given the involvement of rhythmic arm muscle activity in many locomotor tasks. We have previously shown that arm muscle vibrostimulation can elicit non-voluntary upper limb oscillations in unloading body conditions. Here we investigated the excitability of the cervical spinal circuitry by applying different peripheral and central stimuli in healthy humans. The rationale for applying combined stimuli is that the efficiency of only one stimulus is generally limited. We found that low-intensity electrical stimulation of the superficial arm median nerve can evoke rhythmic arm movements. Furthermore, the movements were enhanced by additional peripheral stimuli (e.g., arm muscle vibration, head turns or passive rhythmic leg movements). Finally, low-frequency transcranial magnetic stimulation of the motor cortex significantly facilitated rhythmogenesis. The findings are discussed in the general framework of a brain-spinal interface for developing adaptive central pattern generator-modulating therapies.

Experimentally induced rhythmic jaw muscle activities during non-rapid eye movement sleep in freely moving guinea pigs.

Rhythmic jaw muscle activities frequently occur during non-rapid eye movement sleep in patients with sleep bruxism. The present study aimed to investigate the response characteristics of the masticatory rhythm generation during non-rapid eye movement sleep in animals. Eleven guinea pigs were surgically prepared for polygraphic recordings by electromyography, electrooculography, electroencephalography and electrocardiography with the implantation of a stimulating electrode. Repetitive electrical microstimulations at three intensities were applied to the corticobulbar tract under freely moving conditions. The rhythmic electro-myographic responses of the digastric and masseter muscles were scored and analysed. Changes in cortical electro-encephalographic power and heart rate in association with these stimulations were quantified. Microstimulations to the corticobulbar tract induced rhythmic jaw muscle activities in digastric muscles, occasionally with masseter activities during wakefulness and non-rapid eye movement sleep. The response rate of rhythmic jaw muscle activities was significantly lower (p<0.01) and the response latency was significantly longer (p<0.01) during non-rapid eye movement sleep than during wakefulness. At higher stimulus intensities, the response rate increased and response latency decreased. The mean burst intervals of the digastric and masseter muscles were similar regardless of vigilance states and stimulus intensities. Induced rhythmic jaw muscle activities during non-rapid eye movement sleep were followed by a transient decrease in delta power and increases in beta power and heart rate. During non-rapid eye movement sleep, the masticatory motor system is able to generate rhythmic outputs to the jaw muscles in response to facilitatory inputs although the responsiveness was decreased from wakefulness.

Enabling Task-Specific Volitional Motor Functions via Spinal Cord Neuromodulation in a Human With Paraplegia

We report a case of chronic traumatic paraplegia in which epidural electrical stimulation (EES) of the lumbosacral spinal cord enabled (1) volitional control of task-specific muscle activity, (2) volitional control of rhythmic muscle activity to produce steplike movements while side-lying, (3) independent standing, and (4) while in a vertical position with body weight partially supported, voluntary control of steplike movements and rhythmic muscle activity. This is the first time that the application of EES enabled all of these tasks in the same patient within the first 2 weeks (8 stimulation sessions total) of EES therapy.

Complex Locomotion Behavior Changes Are Induced in Caenorhabditis elegans by the Lack of the Regulatory Leak K+ Channel TWK-7.

The change of locomotion activity in response to external cues is a considerable achievement of animals and is required for escape responses, foraging, and other complex behaviors. Little is known about the molecular regulators of such an adaptive locomotion. The conserved eukaryotic two-pore domain potassium (K2P) channels have been recognized as regulatory K+ channels that modify the membrane potential of cells, thereby affecting, e.g., rhythmic muscle activity. By using the Caenorhabditis elegans system combined with cell-type-specific approaches and locomotion in-depth analyses, here, we found that the loss of K2P channel TWK-7 increases the locomotor activity of worms during swimming and crawling in a coordinated mode. Moreover, loss of TWK-7 function results in a hyperactive state that (although less pronounced) resembles the fast, persistent, and directed forward locomotion behavior of stimulated C. elegans TWK-7 is expressed in several head neurons as well as in cholinergic excitatory and GABAergic inhibitory motor neurons. Remarkably, the abundance of TWK-7 in excitatory B-type and inhibitory D-type motor neurons affected five central aspects of adaptive locomotion behavior: velocity/frequency, wavelength/amplitude, direction, duration, and straightness. Hence, we suggest that TWK-7 activity might represent a means to modulate a complex locomotion behavior at the level of certain types of motor neurons.

Automated detection and characterisation of rumination in sheep using in vivo electrophysiology

Rumination is a precisely timed process that occupies a large part of a sheep's day. The complex motor coordination required to chew and swallow means that quantification of rumination may provide a surrogate marker for effective motor function. Here, data from 24h in vivo electrophysiological recordings, collected as part of an earlier study, were reanalysed for chewing- and swallowing-related activity. The electroencephalographic (EEG) and electromyographic (EMG) data were collected from sheep with surgically-implanted electrodes. An algorithm was designed to detect coordinated, rhythmic muscle activity. This could distinguish episodes of eating from those of rumination. Normal sheep spent ~29% of their time ruminating. Rumination comprised ~40s bouts of regular (~1.7s−1) chewing interspersed by ~6.5s intervals during which time no chewing took place. Eating was significantly less regular than rumination, with quicker chewing (~2.7s−1). Biomarkers for measuring progression of disease would be invaluable for studying neurodegenerative disease such as Huntington's disease (HD). To test the feasibility of using rumination as such a biomarker, we also made recordings from two neurologically impaired sheep. These showed deviations from the pattern of rumination and eating seen in normal sheep. This validates not only our use of rumination as a measure of normal motor function, but also as a surrogate biomarker for measuring motor dysfunction in impaired sheep.

Spinal Cord Stimulation and Augmentative Control Strategies for Leg Movement after Spinal Paralysis in Humans.

Severe spinal cord injury is a devastating condition, tearing apart long white matter tracts and causing paralysis and disability of body functions below the lesion. But caudal to most injuries, the majority of neurons forming the distributed propriospinal system, the localized gray matter spinal interneuronal circuitry, and spinal motoneuron populations are spared. Epidural spinal cord stimulation can gain access to this neural circuitry. This review focuses on the capability of the human lumbar spinal cord to generate stereotyped motor output underlying standing and stepping, as well as full weight-bearing standing and rhythmic muscle activation during assisted treadmill stepping in paralyzed individuals in response to spinal cord stimulation. By enhancing the excitability state of the spinal circuitry, the stimulation can have an enabling effect upon otherwise "silent" translesional volitional motor control. Strategies for achieving functional movement in patients with severe injuries based on minimal translesional intentional control, task-specific proprioceptive feedback, and next-generation spinal cord stimulation systems will be reviewed. The role of spinal cord stimulation can go well beyond the immediate generation of motor output. With recently developed training paradigms, it can become a major rehabilitation approach in spinal cord injury for augmenting and steering trans- and sublesional plasticity for lasting therapeutic benefits.

Detection of sleep bruxism: comparison between an electromyographic and electrocardiographic portable holter and polysomnography

Recent polysomnographic (PSG) studies showed that the sleep bruxism (SB) event is preceded by a sudden shift in autonomic cardiac activity. Therefore, heart rate could be the simplest-to-record parameter for use in addition to portable home EMG monitoring to improve the accuracy in automatic detection of SB events. The aim of the study was to compare the detection of SB episodes by combined surface electromyography and heart rate (HR) recorded by a compact portable device (Bruxoff(®) ), with the scoring of SB episodes by a PSG recording. Twenty-five subjects (14 'probable' bruxers and 11 non-bruxers) were selected for the study. Each subject underwent the Bruxoff and the PSG recordings during the same night. Rhythmic masseter muscle activities (RMMAs) were scored according to published criteria. Correlation coefficients and the Bland-Altman plots were calculated to measure the correlation and agreement between the two methods. Results showed a high correlation (Pearson's r=0·95, P<0·0001) and a high agreement (bias=0·05) between Bruxoff and the PSG. Furthermore, the receiver operating characteristic curve analysis showed a high sensitivity and specificity of the portable device (92·3% and 91·6%, respectively) when the cut-off was set at 4 SB episodes per hour according to published criteria. The Bruxoff device showed a good diagnostic accuracy to differentiate RMMA from other oromotor activities. These findings are important in the light of the need for simple and reliable portable devices for the diagnosis of SB both in the clinical and research settings.