EMG Recordings Research Articles

Classification of Transient Myoelectric Signals for the Control of Multi-Grasp Hand Prostheses

Understanding the neurophysiological signals underlying voluntary motor control and decoding them for controlling limb prostheses is one of the major challenges in applied neuroscience and rehabilitation engineering. While pattern recognition of continuous myoelectric (EMG) signals is arguably the most investigated approach for hand prosthesis control, its underlying assumption is poorly supported, i.e., that repeated muscular contractions produce consistent patterns of steady-state EMGs. In fact, it still remains to be shown that pattern recognition-based controllers allow natural control over multiple grasps in hand prosthesis outside well-controlled laboratory settings. Here, we propose an approach that relies on decoding the intended grasp from forearm EMG recordings associated with the onset of muscle contraction as opposed to the steady-state signals. Eight unimpaired individuals and two hand amputees performed four grasping movements with a variety of arm postures while EMG recordings subsequently processed to mimic signals picked up by conventional myoelectric sensors were obtained from their forearms and residual limbs, respectively. Off-line data analyses demonstrated the feasibility of the approach also with respect to the limb position effect. The sampling frequency and length of the classified EMG window that off-line resulted in optimal performance were applied to a controller of a research prosthesis worn by one hand amputee and proved functional in real-time when operated under realistic working conditions.

Decrease in force steadiness with aging is associated with increased power of the common but not independent input to motor neurons.

Declines in motor function with advancing age have been attributed to changes occurring at all levels of the neuromuscular system. However, the impact of aging on the control of muscle force by spinal motor neurons is not yet understood. In this study on 20 individuals aged between 24 and 75 yr (13 men, 7 women), we investigated the common synaptic input to motor neurons of the tibialis anterior muscle and its impact on force control. Motor unit discharge times were identified from high-density surface EMG recordings during isometric contractions at forces of 20% of maximal voluntary effort. Coherence analysis between motor unit spike trains was used to characterize the input to motor neurons. The decrease in force steadiness with age ( R2 = 0.6, P < 0.01) was associated with an increase in the amplitude of low-frequency oscillations of functional common synaptic input to motor neurons ( R2 = 0.59; P < 0.01). The relative proportion of common input to independent noise at low frequencies increased with variability (power) in common synaptic input. Moreover, variability in interspike interval did not change and strength of the common input in the gamma band decreased with age ( R2 = 0.22; P < 0.01). The findings indicate that age-related reduction in the accuracy of force control is associated with increased common fluctuations to motor neurons at low frequencies and not with an increase in independent synaptic input. NEW & NOTEWORTHY The influence of aging on the role of spinal motor neurons in accurate force control is not yet understood. We demonstrate that aging is associated with increased oscillations in common input to motor neurons at low frequencies and with a decrease in the relative strength of gamma oscillations. These results demonstrate that the synaptic inputs to motor neurons change across the life span and contribute to a decline in force control.

A Novel Time-Domain Descriptor for Improved Prediction of Upper Limb Movement Intent in EMG-PR System.

Electromyogram pattern recognition (EMG-PR) based control is a potential method capable of providing intuitively dexterous control functions in upper limb prostheses. Meanwhile, the feature extraction method adopted in EMG-PR based control is considered as an important factor that influences the performance of the prostheses. By exploiting the limitations of the existing feature extraction methods, this study proposed a new feature extraction method to effectively characterize EMG signal patterns associated with different limb movement intent. The performance of the proposed 2-dimensional novel time-domain feature set (NTDFS) was investigated using classification accuracy and feature space separability metrics across five subjects' EMG recordings, and compared with four different existing methods. In comparison to four other previously proposed feature extraction methods, the NTDFS achieved significantly better performance with increment in accuracy in the range of 5.20% ∼ 8.40% at p<0.05. Additionally, by applying principal component analysis (PCA) technique, the PCA feature space for NTDFS show obvious class separability in comparison to the other existing feature extraction methods. Thus, the proposed NTDFS may facilitate the development of accurate and robust clinically viable EMG-PR based prostheses.

Effects induced by motor cortex anodal transcranial direct current stimulation on wrist muscles in stroke patients

Transcranial direct current stimulation is used to modify noninvasively cortical brain excitability in humans. It consists in delivering a weak current trough two electrodes: one applied over the motor cortex and a second in supra-orbital position. Recently we showed in healthy subjects that anodal tDCS applied over the motor cortex can be used to modify descending inputs relayed by corticospinal tract on reciprocal inhibition pathways innervating wrist muscles [1] . We found that effects induced by anodal tDCS in wrist extensors and in wrist flexors are opposite: tDCS increases reciprocal inhibition in extensors but decreases reciprocal inhibition in flexors. It appears that modulations induced by anodal tDCS on reciprocal inhibition pathways favor the contraction in wrist extensors. Motor deficit in wrist extensors is usual in hemiplegic patients and the aim of this study is to combine spinal cord MRI and electrophysiological methods to explore effects of tDCS at wrist level in patients with impaired wrist motor control. Anodal tDCS is applied over the non-lesional hemisphere (ipsilateral motor cortex). Its effects at spinal level are explored using electrophysiological techniques based on EMG recordings and percutaneous stimulations of peripheral nerves to elicit reciprocal inhibition at wrist level. MRI study relies on diffusion tensor imaging (DTI) and magnetization transfer (MT) [2] . Preliminary results in hemiplegic patients suggest an increase of reciprocal inhibition contrary to the results found in healthy subjects. They also show a relationship between motor impairment and MRI metrics. It opens new vista for motor rehabilitation of stroke patients.

Feature Selection for the Detection of Sleep Apnea using Multi-Bio Signals from Overnight Polysomnography.

Patients with sleep apnea (SA) are at increased risk of stroke and cardiovascular disease. Diagnosis of sleep apnea depends on the standard overnight polysomnography (PSG). In this study, the DREAM Apnea Database was used to evaluate the importance of the various features proposed in the literature for the analysis of sleep apnea. Various timeand frequency- domain features that include wavelet and power spectral density were extracted from ECG, EMG, EEG, airflow, SaO2, abdominal and thoracic recordings. Evaluation measures of one-way analysis of variance (ANOVA) and Rank-Sum test were used to test the performance of different features. The selected feature subset indicated that frequency-domain features outperform time-domain ones. This study will help in enhancing the detection accuracy of sleep apnea for the various polysomnography signals.

Hybrid robotic system combining passive exoskeleton and functional electrical stimulation for upper limb stroke rehabilitation: Preliminary results of the retrainer multi-center randomized controlled trial

Stroke is the main cause of acquired adult disability with major impact on arm function. The combined use of Functional Electrical Stimulation (FES) and robotic technologies is strongly advocated to improve rehabilitation outcomes after stroke. We present the preliminary data of a multi-center Randomized Controlled Trial aimed at evaluating the effectiveness of this system with respect to conventional therapy for sub-acute stroke upper limb rehabilitation. The RETRAINER system consists of a lightweight and non-cumbersome passive arm exoskeleton for weight relief, a current-controlled stimulator with 2 channels of stimulation and 2 channels of EMG recordings. In this work we are presenting the preliminary results of 39 sub-acute stroke patients with a distance from the acute event between two weeks and nine months. The inclusion criteria was: age between 18 and 85 years, Motricity Index (MI) < 80%, muscular activity for arm and shoulder at least 1 Medical Research Council (MRC) with a visible contraction, no joint limitation, pain or spasticity. They were randomized in two group: 1 conventional rehabilitation methods, 2 experimental group using Retrainer System. Each participant performed 9 weeks of treatment 3 times for week. We measured MI, Action Research Arm Test (ARAT) and Motor Activity Log (MAL) at beginning (T0) and at the end of treatment (T1). Results are showed in the next Table 1 . Both groups showed statistical improvement in outcome measures. Experimental group showed a statistical better improvement regarding time and group effect.

Properties of short-latency responses in the upper limbs evoked by axial impulses during leaning: evidence for reticulospinal projections.

We studied the short-latency (SL) effects of postural perturbations produced by impulses applied over the spine of the C7 vertebra or the sternum ("axial impulses") in 12 healthy subjects. EMG recordings were made bilaterally from the triceps brachii, biceps brachii, soleus, and tibialis anterior muscles, and unilaterally from the deltoid, forearm flexors, forearm extensors, and first dorsal interosseous (FDI) muscles. Sternal impulses evoked short-latency responses in the biceps when subjects leaned posteriorly to support approximately 12% of their body weight with the arms, but these responses were only modestly larger than for isometric contraction of the arms (26.3 vs. 14.7%). In contrast, clear excitatory responses could be evoked in the deltoid, triceps, forearm muscles, and FDI when leaning anteriorly to support similar amounts of body weight. These responses were significantly larger than during isometric contraction. The deltoid (42.5%) and triceps (44.7%) had the largest responses in supported anterior lean and onset latencies increased distally in this condition (mean 31.8ms in deltoid to 53.7ms in FDI). There was a disproportionate delay between the forearm muscles and FDI. For both directions of lean, postural reflex responses normally present in the legs were severely attenuated. SL upper limb excitatory responses were bigger in proximal muscles as well as larger and more widespread for anterior axial perturbations compared to posterior axial perturbations when using the arms to support body weight. Our findings also provide further evidence of a role for reticulospinal pathways in mediating these rapid postural responses to accelerations of the trunk.

Influence of lateral pedal translation on muscle recruitment and kinematics in cyclists

Background/ObjectiveCurrent cycling pedals constrain the pedaling motion to the sagittal plane. This study aimed to evaluate novel pedal systems that allow lateral translation through the pedal stroke via frontal plane kinematics and muscle recruitment. MethodsSixteen cyclists were recruited to pedal on three pedal systems: standard pedals (STD), free lateral translation (LAT), and a guided lateral translation pedal (VL). Frontal plane kinematics were measured via markers on the hip, knee, and foot. EMG recordings were collected from 8 leg muscles and expressed as a percentage of functional threshold power activation levels. ResultsKnee and ankle range of movement was significantly more highly correlated in the VL pedals compared to STD (r = .46 ± .08, vs. .23 ± .05; p = .028). The rectus femoris was recruited significantly less in the VL vs. STD pedals (23.6 ± 7.7% lower, p = .008). The hip abductors were more highly recruited in VL vs. STD: gluteus medius (16.9 ± 7.2% higher, p = .033) and the tensor fascia latae (30.9 ± 8.5% lower, p = .003). ConclusionVL pedals may improve knee-to-ankle tracking through the pedal stroke and may allow cyclists to increase power output through the additional recruitment of hip abductors.

A Fully Integrated 11.2-mm2 a-IGZO EMG Front-End Circuit on Flexible Substrate Achieving Up to 41-dB SNR and 29-M$\Omega$ Input Impedance

A biopotential front-end (FE) circuit is designed and fabricated using amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs on flexible plastic substrate. Its input chopper provides both noise reduction and frequency division multiplexing among multiple FEs in an array. Measurements of the FE at chopping frequencies from 5 to 8 kHz show a gain in the range of 24.9–23.1 dB, bandwidth of 5.4–5.2 kHz, input noise in the EMG band ranging from $125~{\mu } {V}_{\text {RMS}}$ to $31.4~{\mu } {V}_{\text {RMS}}$ , and an input impedance of 29.6–23 $\text{M}{\Omega }$ . At different chopping frequencies, the SNR in the EMG band is respectively, 29, 32.3, 38, and 41 dB, enough to monitor muscle fiber conduction velocity. This is achieved in a total area of 11.2 mm2 and with 1.3-mW power consumption. In-vivo recordings of EMG from the forearm of a person using the fabricated FE and standard gel electrodes have been performed. The measurements show EMG bursts with a maximum amplitude of 1.6 mV, which is within the physiological range for this muscle. The proposed circuit achieves an $8.9 {\times }$ reduction in size compared to previous FEs fabricated on flexible foil for EMG applications, enabling a spatial resolution in the order of a few millimeters, with great benefit for the diagnosis of neuromuscular disorders.

T48. Hypersensitivity of the persistent inward current

Motor cortex controls movements but a sensitive mechanism called persistent inward current (PIC) at the spinal cord plays a major role in adjusting the strength. The PIC is subject to descending neuromodulatory systems but also peripheral sensory afferent activity. Hypersensitivity of PIC may cause spasms which are stimulation sensitive. We describe a 46-year old male patient who had frequent and severe but relatively short-lasting bouts of stimulus-sensitive spasms after a suspected myelitis 10 years earlier. Stiff person syndrome and channelopathy of the muscle membrane were closed out. The spasms were very therapy resistant and intrathecal baclofen therapy was planned. A six-channel surface EMG recording of the right upper extremity (muscles: opponens pollicis, abductor digiti minimi, flexor carpi radialis, extensor carpi radialis, biceps brachii, triceps brachii) and repeated serial electrical stimuli of the radial nerve (30 Hz, 10 mA, 50 stimuli) and the median nerve at wrist (30 Hz, 6 mA, 50 stimuli) and vibratory stimulation of muscles. H-reflex measurements of the median nerve and needle EMG recordings during spasms. The serial, but not single, electrical stimuli caused activation of all the recorded muscles with different delay times ranging from 250 to 2500 ms. We saw augmentation of the responses with shortening delay times with repeated serial stimuli. Vibratory stimulation of the abductor digiti minimi muscle also caused activation of all the muscles recorded but with little augmentation. Vibratory stimulus of the biceps brachii muscle caused a very strong contraction of all the muscles recorded. This stimulus could not be repeated because of the strong response. The post-stimulus contractions were confined to the right upper extremity. EMG recorded with needle during spasms resembled normal muscle activity. When measuring the median nerve H-reflex, getting an M-response increased the amplitude of H-reflex. With this patient we could reveal typical behavior of PIC hypersensitivity to peripheral stimuli. The delay times of stimulus-sensitive motor reactions of different muscles varied but they were relatively long indicating the involvement of a neuromodulatory system (G-proteins, intracellular cascades) instead of the ionotrophic activation. The responses were confined to one extremity. Serial stimuli of both A beta and A alpha sensory axons caused reactions. We saw augmentation of the responses and shortening of the delay times with repeated serial or vibratory stimuli. The motor contractions lasted for a few minutes at most and were mainly tonic. Measurements of H-reflex showed that even a small muscle afferent activation caused an increased PIC response. EMG during spasms resembled normal muscle activation. With these features hypersensitivity of PIC can be diagnosed and differentiated from other syndromes with sustained motor symptoms.

Recording characteristics of electrical impedance-electromyography needle electrodes

Objective: Needle EMG remains the standard clinical test for neuromuscular disease (NMD) assessment, but it only characterizes myofiber membrane depolarization. On the other hand, electrical impedance provides non-electrically active structural and compositional data of tissues. Here, we designed a prototype of needle electrode integrating electrical impedance and EMG measurement capabilities, the so-called I-EMG needle electrode. Approach: We use finite element method models to study the impedance recording characteristics of I-EMG needle electrodes. The simulated electrical and mechanical design specifications are then manufactured to create a prototype of an I-EMG needle electrode. We pilot these new needle electrodes by conducting in vivo impedance measurements with muscle at rest on healthy wild-type (wt, n = 5) and muscular dystrophy (mdx, n = 5) mice. Comparisons between wt and mdx mice are performed using Mann–Whitney test, two-tailed, p < 0.05. The electrical characterization of the EMG electrode in the developed I-EMG needles was performed in vitro on saline solution and through EMG detection in wt animal at rest and during voluntary contractions. Results: Muscle impedance demonstrate good repeatability (p < 0.05 and p < 0.005 for resistance and reactance at 50 kHz, respectively) and agreement between different I-EMG needles. Impedance data allows us to discriminate between mdx and wt muscle (p < 0.05 and p < 0.005 for resistance and reactance at 10 kHz, respectively). EMG broadband noise power and peak amplitude using the I-EMG needle were similar to that of a commercial monopolar EMG needle. EMG recordings using the I-EMG needle measured electrical activity similar to a standard monopolar needle with muscle at rest and during voluntary contraction. Significance: Needle I-EMG technology may offer the opportunity to enhance the diagnostic capability and quantification of NMD beyond that possible with either impedance or EMG techniques separately. Ultimately, needle I-EMG could serve as a new bedside tool to assess NMD without increasing the complexity or duration of the EMG test.

T128. Modulation of exteroceptive electromyographic responses in defensive peripersonal space

Introduction The cutaneous silent period (CSP) is a spinal nociceptive inhibitory reflex, that briefly interrupts voluntary contraction of limb muscles involved in reaching and grasping movements after noxious electrical stimulation of a cutaneous nerve. It is mediated by A-delta afferents. CSPs act in conjunction with flexor withdrawal reflexes to constitute a sophisticated defensive system for protecting a limb from harmful stimuli. CSP is functionally rather than anatomically organized. I1 and I2 components are considered spinal, E2 is regarded transcortical in origin. Defending the body surface from environmental threats requires sensorimotor integration between multimodal sensory afferents and motor planning of defensive movements. Cortical areas involved in this integration are the poly-sensory zone in the precentral gyrus and the ventral intraparietal area. The defensive peri-personal space (DPPS), immediately surrounding the body, was first described in macaque monkeys. Neurophysiological studies of the human DPPS demonstrated larger somatosensory blink reflexes with the stimulated hand located near the face. We investigated the effect of hand position on CSP in DPPS vs. extrapersonal space (EPS). Methods Fifteen healthy volunteers underwent serial CSP testing with the arm resting on an elevated table, elbow flexed, and the hand held either within 5 cm from the nose (NEAR) or away from the body (FAR). Electrical stimuli were applied to either digit 2 or 5 (D2, D5). Sensory thresholds (ST) were established for each subject and digit. EMG recordings were obtained from first dorsal interosseous (FDI) muscle during 20% maximal voluntary contraction, following random stimulation of either D2 or D5 in both NEAR and FAR conditions, with 5, 10, and 15X ST intensity. CSPs were identified by a decrease in mean rectified EMG activity below 80% of prestimulus baseline. CSPs were divided into I1, E2, and I2. Results Following D2 stimulation, CSPs consisted of I1, E2, and I2. With increasing stimulus intensities, CSP duration and I2 duration increased, suppression index (SI) of CSP and I2 decreased, and E2 amplitude decreased progressively, both in DPPS and EPS. E2 amplitude was significantly larger in DPPS vs. EPS, while no other parameter differed between DPPS and EPS. Following D5 stimulation, CSP equaled I2, and there was no clear E2. With increasing stimulus intensities I2 duration increased and SI decreased, both in DPPS and EPS. No parameter differed between DPPS and EPS. Conclusion Concurring with previous literature, E2 was present in FDI only when stimulating homotopic D2 and not heterotopic D5. E2 was larger in DPPS vs. EPS, representing direct neurophysiological evidence of transcortical sensorimotor processing related to DPPS, while inhibitory CSP parameters did not differ between DPPS and EPS, concurring with a spinal organization of its circuitry.

Motor Unit Discharge Characteristics And Walking Performance Of Individuals With Multiple Sclerosis.

PURPOSE: To examine the associations between strength, force steadiness, and motor unit discharge characteristics of lower leg muscle with assessments of walking performance and disability status in individuals with multiple sclerosis (MS). METHODS: Persons with MS (n=23, 9 men, 53 ± 7 yrs) attended 1 to 3 evaluation sessions that were performed before, immediately after, and 4 wks after a clinical trial of neuromuscular electrical stimulation. Outcomes included 3 questionnaires (Patient Determined Disease Steps [PDDS], Modified Fatigue Impact Scale [MFIS], and MS Walking Scale-12 [MSWS-12]), 25-ft walk test, 6-min walk test, and maximal torque and force steadiness (10 and 20% MVC) for lower leg muscles. High-density surface EMG recordings were obtained from the tibialis anterior (TA), soleus (Sol), and medial gastrocnemius (MG) during the steady contractions and decomposed into discharge times of motor unit action potentials. RESULTS: Greater levels of self-reported disability (PDDS, MFIS, MSWS-12) were associated with less distance walked in 6 min and longer times to walk 25 ft. Mean interspike intervals (ISI) were 110 ± 23 ms and 102 ± 22 ms (10% and 20% MVC force, respectively) for TA motor units (n= 1,634), 138 ± 36 ms and 135 ± 34 ms for MG motor units (n=696), and 150 ± 33 ms and 145 ± 34 ms for Sol motor units (n = 902). A multiple regression model explained 40% (P=0.001) of the variance in 6-min distance with two predictor variables: mean ISI of MG (partial r = -0.48) and MVC dorsiflexor torque of the more affected leg (partial r=0.37). Similarly, another multiple regression model explained 47% of the variance (P<0.001) in 25-ft time with three predictor variables: mean ISI of soleus (partial r=0.51), MVC dorsiflexor torque of the more affected leg (partial r = -0.43), and force steadiness of the plantar flexors (partial r = 0.39). CONCLUSION: Moderate amounts of the variance in two walking tests for persons with MS were explained by mean discharge times of action potentials by motor units in plantar flexor muscles during steady submaximal contractions, the strength of the dorsiflexor muscles in the more affected leg, and force steadiness during an isometric contraction. This research was supported by the Eunice Kennedy Shriver National Institute of Child Health & Human Development of the NIH (R03HD079508).

F59. Spasmodic reflex myoclonus-an characteristic electrophysiological manifestation for the diagnosis of Stiff-person syndrome

Introduction Stiff person syndrome (SPS) is a rare disease entity and the pivotal clinical features contain progressive course of fluctuating stiffness of the low back and lower limbs. Progressive encephalomyelitis with rigidity and myoclonus (PERM) is one of the unique variants of stiff person syndrome, and it was characterized with rigidity, stimulus-sensitive spasms, myoclonus, autonomic disturbance, and brainstem signs. These features resemble those of hyperekplexia. The accurate diagnosis of SPS is difficult but is crucial for the in time intervention with immunotherapy for life saving. In addition to the detection of responsible antibody, clinical electrophysiological manifestation, spasmodic reflex myoclonus, would be of great help in establishing the diagnosis. Methods Multichannel surface electromyogram (sEMG) and accelerometer recordings were conducted over the lumbar paraspinalis, rectus abdominalis, quadriceps, and hamstring muscles. Stimulus sensitive phenomenon was illustrated with accelerometer tapped over the pinprick. The signals were processed and digitized with CED power1401 with Spike2. The band pass for sEMG was set from 80 Hz to 1000 Hz. Results The results demonstrated that episodes of spontaneous onset of spasm of the low trunk and legs lasted about seconds to minutes. Stimuli with nose tip tapping, would elicit vigorous jerks with dissemination of long lasting muscle spasm of the neck, paraspinal muscle, rectus abdominalis muscle, to quadriceps and hamstring muscles in a descending spreading pattern. The unique electrophysiological manifestations illustrate the characteristic feature of spasmodic reflex myoclonus. The surface EMG recording also showed the phenomena of habituation, in which a trend of amplitude decrescendo from the first toward the third EMG responses were observed during consecutive auditory stimulus. The serum levels of anti-glutamic acid decarboxylase 65 antibodies was 164 IU. Conclusion The unique EMG pattern can help identify SPS. The clinical features of spasmodic reflex myoclonus are similar to hyperekplexia. However, there are some differences between the two phenomena. Unlike hyperekplexia, the spasmodic reflex myoclonus can be habituated after repetitive stimulation in the SPS patient. Furthermore, the initial myoclonic bursts of spasmodic reflex myoclonus were not present in hyperekplexia and the EMG burst duration was much shorter of the hyperekplexia as compared with that of spasmodic reflex myoclonus. These neurophysiological features discern spasmodic reflex myoclonus from hyperekplexia and are helpful in making diagnosis of SPS.

993 - Wireless Anal Sphincter EMG Recording to Assess Dyssynergic Defecation: The Effects of Posture and Privacy

993 - Wireless Anal Sphincter EMG Recording to Assess Dyssynergic Defecation: The Effects of Posture and Privacy

Respiratory EMG responsiveness to hypercapnic hypoxia in mdx mice

Duchenne muscular dystrophy (DMD) is a fatal neuromuscular disease characterised by the absence of the structural protein dystrophin. Respiratory failure is the leading cause of premature death in DMD. Although respiratory insufficiency is recognized as a hallmark of DMD, respiratory control is relatively understudied. We hypothesized that enhanced drive in accessory respiratory motor pathways preserves ventilatory capacity compensating for severe respiratory muscle weakness.We utilised the C57BL/10ScSn‐Dmdmdx/J (mdx) mouse model. Respiratory flow recordings were performed in freely‐behaving wild‐type (WT, n=9) and mdx (n=7) mice at ~8 weeks of age using whole‐body plethysmography to determine ventilation (VE), oxygen consumption (VO2) and carbon dioxide production (VCO2). Baseline recordings were performed in normoxia, followed by chemostimulation using hypercapnic hypoxic gas challenge (FiO2=0.10; FiCO2=6; balance N2). In urethane (1.6 g/kg) anaesthetised WT (n=13) and mdx (n=14) mice, diaphragm, intercostal and genioglossus EMG and motor unit recordings were performed during baseline conditions and in response to chemostimulation.Plethysmographic recordings revealed that during chemostimulation, minute ventilation (VE) is equivalent in WT and mdx mice, highlighting a considerable ventilatory reserve in young mdx despite substantial diaphragm muscle weakness. Moreover, diaphragm, intercostal and genioglossus EMG responsiveness to hypercapnic hypoxia was equivalent in WT and mdx mice.Despite substantial diaphragm weakness and evidential muscle fibre damage and remodelling, freely behaving mdx mice can achieve enhanced ventilation during chemostimulation to levels equivalent to that of WT animals. We found no evidence of enhanced activity in respiratory muscle EMGs. Assessment of the motor unit population will allow for the comparison of the phenomena of rate coding and recruitment during increased respiratory muscle activation. Our study suggests that respiratory muscle weakness in young mdx does not compromise ventilator behaviour but is likely to have considerable impact on airway protective behaviours.Support or Funding InformationDepartment of Physiology, University College Cork, Cork, IrelandThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Antagonism of corticotropin releasing factor in the basolateral amygdala of resilient and vulnerable rats: Effects on fear-conditioned sleep, temperature and freezing

The basolateral nucleus of the amygdala (BLA) plays a significant role in mediating individual differences in the effects of fear memory on sleep. Here, we assessed the effects of antagonizing corticotropin releasing factor receptor 1 (CRFR1) after shock training (ST) on fear-conditioned behaviors and sleep. Outbred Wistar rats were surgically implanted with electrodes for recording EEG and EMG and with bilateral guide cannulae directed at BLA. Data loggers were placed intraperitoneally to record core body temperature. The CRFR1 antagonist, antalarmin (ANT; 4.82 mM) was microinjected into BLA after shock training (ST: 20 footshocks, 0.8 mA, 0.5 s duration, 60 s interstimulus interval), and the effects on sleep, freezing and the stress response (stress-induced hyperthermia, SIH) were examined after ST and fearful context re-exposure alone at 7 days (CTX1) and 21 days (CTX2) post-ST. EEG and EMG recordings were scored for non-rapid eye movement sleep (NREM), rapid eye movement sleep (REM) and wakefulness. The rats were separated into 4 groups: Vehicle-vulnerable (Veh-Vul; n = 10), Veh-resilient (Veh-Res; n = 11), ANT-vulnerable (ANT-Vul; n = 8) and ANT-resilient (ANT-Res; n = 8) based on whether, compared to baseline, the rats showed a decrease or no change/increase in REM during the first 4 h following ST. Post-ST ANT microinjected into BLA attenuated the fear-conditioned reduction in REM in ANT-Vul rats on CTX1, but did not significantly alter REM in ANT-Res rats. However, compared to Veh treated rats, REM was reduced in ANT treated rats on CTX2. There were no group differences in freezing or SIH across conditions. Therefore, CRFR1 in BLA plays a role in mediating individual differences in sleep responses to stress and in the extinction of fear conditioned changes in sleep.

Modulation of task-related cortical connectivity in the acute and subacute phase after stroke.

The functional relevance of cortical reorganization post-stroke is still not well understood. In this study, we investigated task-specific modulation of cortical connectivity between neural oscillations in key motor regions during the early phase after stroke. EEG and EMG recordings were examined from 15 patients and 18 controls during a precision grip task using the affected hand. Each patient attended two sessions in the acute and subacute phase (median of 3 and 34days) post-stroke. Dynamic causal modelling (DCM) for induced responses was used to investigate task-specific modulations of oscillatory couplings in a bilateral network comprising supplementary motor area (SMA), dorsal premotor cortex (PMd) and primary motor cortex (M1). Fourteen models were constructed for each subject, and the input induced by the experimental manipulation (task) was set to inferior parietal lobule (IPL). Bayesian model selection favoured a fully connected model. A reduced coupling from SMA and intact M1 in the γ-band (31-48Hz) to lesioned M1 in the β-band (15-30Hz) was observed in patients in the acute phase compared to controls. Behavioural performance improved significantly in the subacute phase, while an increased positive coupling from intact PMd to lesioned M1 and a less negative modulation from lesioned M1 to intact M1 were observed for patients compared to controls both from the γ-band to the β-band. We infer that the observed differences in cross-frequency cortical interactions are important for functional recovery.

On the electrode positioning for bipolar EMG recording of forearm extensor and flexor muscle activity after transcranial magnetic stimulation

After stroke, motor pathways are often affected, leading to paresis. It remains difficult to reliably predict motor recovery of the upper extremity, for which transcranial magnetic stimulation (TMS) may add to clinical examination. Placement of the surface electromyography (sEMG) electrodes in TMS is essential for information about specific muscle groups and corticospinal pathways. This study primarily aimed to determine the optimal sEMG electrode positions for recording activity of forearm flexor and extensor muscles. The first goal was to optimize sensitivity in measuring any motor evoked potentials (MEP), because they may be reduced or absent in stroke patients. The second goal was adequate distinction between forearm flexor and extensor muscle groups. For optimal flexibility in choosing montages, a multichannel sEMG set-up with 37 electrodes encircled the forearm. The determination of optimal pairs was based upon electrical peripheral nerve stimulation. We found pairs with the highest compound nerve action potential (CMAP) amplitudes and pairs that optimally distinguished between the flexor and extensor muscles. Large interelectrode distances lead to responses with larger amplitudes and therefore sensitively measure any remaining corticomuscular connections. As a follow-up, specific muscle group responses can be targeted with smaller interelectrode distances. In conclusion, this study helps to identify better electrode locations for the use of clinical TMS studies.

Deletion of Trace Amine-Associated Receptor 1 Attenuates Behavioral Responses to Caffeine.

Trace amines (TAs), endogenous amino acid metabolites that are structurally similar to the biogenic amines, are endogenous ligands for trace amine-associated receptor 1 (TAAR1), a GPCR that modulates dopaminergic, serotonergic, and glutamatergic activity. Selective TAAR1 full and partial agonists exhibit similar pro-cognitive, antidepressant- and antipsychotic-like properties in rodents and non-human primates, suggesting TAAR1 as a novel target for the treatment of neurological and psychiatric disorders. We previously reported that TAAR1 partial agonists are wake-promoting in rats and mice, and that TAAR1 knockout (KO) and overexpressing mice exhibit altered sleep-wake and EEG spectral composition. Here, we report that locomotor and EEG spectral responses to the psychostimulants modafinil and caffeine are attenuated in TAAR1 KO mice. TAAR1 KO mice and WT littermates were instrumented for EEG and EMG recording and implanted with telemetry transmitters for monitoring locomotor activity (LMA) and core body temperature (Tb). Following recovery, mice were administered modafinil (25, 50, 100 mg/kg), caffeine (2.5, 10, 20 mg/kg) or vehicle p.o. at ZT6 in balanced order. In WT mice, both modafinil and caffeine dose-dependently increased LMA for up to 6 h following dosing, whereas only the highest dose of each drug increased LMA in KO mice, and did so for less time after dosing. This effect was particularly pronounced following caffeine, such that total LMA response was significantly attenuated in KO mice compared to WT at all doses of caffeine and did not differ from Vehicle treatment. Tb increased comparably in both genotypes in a dose-dependent manner. TAAR1 deletion was associated with reduced wake consolidation following both drugs, but total time in wakefulness did not differ between KO and WT mice. Furthermore, gamma band EEG activity following both modafinil and caffeine treatment was attenuated in TAAR1 KO compared to WT mice. Our results show that TAAR1 is a critical component of the behavioral and cortical arousal associated with two widely used psychostimulants with very different mechanisms of action. Together with our previous findings, these data suggest that TAAR1 is a previously unrecognized component of an endogenous wake-modulating system.