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State-dependent non-invasive brain stimulation (NIBS) informed by electroencephalography (EEG) has contributed to the understanding of NIBS inter-subject and inter-session variability. While these approaches focus on local EEG characteristics, it is acknowledged that the brain exhibits an intrinsic long-range dynamic organization in networks. This proof-of-concept study explores whether EEG connectivity of the primary motor cortex (M1) in the pre-stimulation period aligns with the Motor Network (MN) and how the MN state affects responses to the transcranial magnetic stimulation (TMS) of M1. One thousand suprathreshold TMS pulses were delivered to the left M1 in eight subjects at rest, with simultaneous EEG. Motor-evoked potentials (MEPs) were measured from the right hand. The source space functional connectivity of the left M1 to the whole brain was assessed using the imaginary part of the phase locking value at the frequency of the sensorimotor μ-rhythm in a 1 s window before the pulse. Group-level connectivity revealed functional links between the left M1, left supplementary motor area, and right M1. Also, pulses delivered at high MN connectivity states result in a greater MEP amplitude compared to low connectivity states. At the single-subject level, this relation is more highly expressed in subjects that feature an overall high cortico-spinal excitability. In conclusion, this study paves the way for MN connectivity-based NIBS. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the validity of intraoperative evoked potential (EP) including motor evoked potential (MEP) and somatosensory evoked potentials (SEP) as a biomarker for predicting neural function changes after thoracic spinal decompression (TSD) surgery. Method: A consecutive series of 336 TSD surgeries were reviewed between 2010 and 2021 from four spine center. All patients with TSD were divided into 3 groups according to different intraoperative EP results: group 1, EP alerts; group 2, no obvious EP deterioration; group 3, EP improvement compared with baselines. The lower limb Japanese Orthopedic Association (JOA) scores (as well as early and long-term JOA recovery rate) were utilized to quantitatively assess pre- and postoperative neural function change. Results: Among the 3 subgroups according to the different EP changes, the early JOA recovery rate (RR%) in the EP improvement group was significantly better than the other two groups (51.3 ± 58.6* vs. 27.5 ± 31.2 and 33.3 ± 43.1; p < 0.01) after 3-month follow-up. The mean MEP and SEP amplitude were from 116 ± 57 µV to 347 ± 71 µV (p < 0.01) and from 1.86 ± 0.24 µV to 2.65 ± 0.29 µV (p < 0.01) between spinal cord pre-decompression and post-decompression. Moreover, multivariate logistic regression analysis revealed that risk factors of EP improvement were duration of symptom (p < 0.001, OR 10.9) and Preop. neurologic deficit degree (p = 0.013, OR 7.46). Conclusion: The intraoperative EP can predict postoperative neural function changes as a biomarker during TSD. Patient with EP improvement probably has better prognosis for early neural function recovery. The duration of symptom and preoperative neurologic deficit degree may be related to intraoperative EP improvement. [ABSTRACT FROM AUTHOR]

Intraoperative neurophysiological monitoring (IONM) provides data on the state of neurological functionality. However, the current state of technology impedes the reliable and timely extraction and communication of relevant information. Advanced signal processing and machine learning (ML) technologies can develop a robust surveillance system that can reliably monitor the current state of a patient's nervous system and promptly alert the surgeons of any imminent risk. Various ML and signal processing tools can be utilized to develop a real-time, objective, multi-modal IONM based-alert system for spine surgery. Next generation systems should be able to obtain inputs from anesthesiologists on vital sign disturbances and pharmacological changes, as well as being capable of adapting patient baseline and model parameters for patient variability in age, gender, and health. It is anticipated that the application of automated decision guiding of checklist strategies in response to warning criteria can reduce human work-burden, improve accuracy, and minimize errors.

State-dependent non-invasive brain stimulation (NIBS) informed by electroencephalography (EEG) has contributed to the understanding of NIBS inter-subject and inter-session variability. While these approaches focus on local EEG characteristics, it is acknowledged that the brain exhibits an intrinsic long-range dynamic organization in networks. This proof-of-concept study explores whether EEG connectivity of the primary motor cortex (M1) in the pre-stimulation period aligns with the Motor Network (MN) and how the MN state affects responses to the transcranial magnetic stimulation (TMS) of M1. One thousand suprathreshold TMS pulses were delivered to the left M1 in eight subjects at rest, with simultaneous EEG. Motor-evoked potentials (MEPs) were measured from the right hand. The source space functional connectivity of the left M1 to the whole brain was assessed using the imaginary part of the phase locking value at the frequency of the sensorimotor μ-rhythm in a 1 s window before the pulse. Group-level connectivity revealed functional links between the left M1, left supplementary motor area, and right M1. Also, pulses delivered at high MN connectivity states result in a greater MEP amplitude compared to low connectivity states. At the single-subject level, this relation is more highly expressed in subjects that feature an overall high cortico-spinal excitability. In conclusion, this study paves the way for MN connectivity-based NIBS.

Background/Purpose: Paired stimulation can cause neuroplasticity in corticospinal and spinal pathways in subjects with a chronic spinal cord injury (SCI). We aimed to know the effects of different waveforms using paired stimulations with bicycling in subjects with a chronic SCI. Methods: Recruited subjects with an SCI underwent three treatment interventions in random order for 4–20 min followed by 30 min of bicycling (control, repetitive transcranial magnetic stimulation (TMS; rTMS) at 20 Hz with transspinal direct current stimulation (tsDCS), and intermittent theta burst stimulation (iTBS) with tsDCS with a 1-week gap period. A TMS method was employed to record the resting motor threshold (RMT), the 90% values of which was used as the stimulation intensity, and the Hoffman (H)-reflex was measured by stimulating the tibial nerve in the popliteal fossa. The RMT, motor evoked potential (MEP) latency, MEP peak-to-peak amplitude, and H-reflex latency as primary variables and lower extremity motor scale (LEMS) and modified Ashworth spasticity scale (MAS) as secondary variables were analyzed before and after the interventions. Results: The MEP latency, MEP amplitude, and LEMS significantly improved with the rTMS-iTBS/tsDCS or the rTMS-20 Hz/tsDCS (p < 0.050) protocols compared to the control intervention. All other outcome measures, including RMT, H-reflex latency, and MAS score showed some changes but did not fully attain a level of significance. Conclusion: The paired stimulation with rTMS-iTBS/tsDCS was equally effective to produce neuroplastic effect in subjects with chronic SCI compared to the conventional TMS-20 Hz/tsDCS intervention.

Abstract Background Lots of studies have measured motor evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) in anesthetized animals. However, in awake animals, the measurement of TMS-induced MEP is scarce as lack of sufficient restraint. So far, the explicit study of anesthesia effects on corticospinal excitability and repetitive TMS (rTMS) induced modulation is still lacking. This study aimed to: (1) measure TMS-induced MEP in both awake restrained and anesthetized rats, (2) investigate the effect of anesthesia on corticospinal excitability, and (3) on rTMS-induced modulation. Methods MEP of eighteen rats were measured under both wakefulness and anesthesia using flexible binding and surface electrodes. Peak-to-peak MEP amplitudes, resting motor threshold (RMT) and the slope of stimulus response (SR) were extracted to investigate anesthesia effects on corticospinal excitability. Thereafter, 5 or 10 Hz rTMS was applied with 600 pulses, and the increase in MEP amplitude and the decrease in RMT were used to quantify rTMS-induced modulation. Results The RMT in the awake condition was 44.6 ± 1.2% maximum output (MO), the peak-to-peak MEP amplitude was 404.6 ± 48.8 μV at 60% MO. Under anesthesia, higher RMT (55.6 ± 2.9% MO), lower peak-to-peak MEP amplitudes (258.6 ± 32.7 μV) and lower slope of SR indicated that the corticospinal excitability was suppressed. Moreover, under anesthesia, high-frequency rTMS still showed significant modulation of corticospinal excitability, but the modulation of MEP peak-to-peak amplitudes was weaker than that under wakefulness. Conclusions This study measured TMS-induced MEP in both awake and anesthetized rats, and provided explicit evidence for the inhibitory effects of anesthesia on corticospinal excitability and on high-frequency rTMS-induced modulation of MEP.

Mental imagery is a powerful capability that engages similar neurophysiological processes that underlie real sensory and motor experiences. Previous studies show that motor cortical excitability can increase during mental imagery of actions. In this study, we focused on possible inhibitory effects of mental imagery on motor functions. We assessed whether imagined arm paralysis modulates motor cortical excitability in healthy participants, as measured by motor evoked potentials (MEPs) of the hand induced by near‐threshold transcranial magnetic stimulation (TMS) over the primary motor cortex hand area. We found lower MEP amplitudes during imagined arm paralysis when compared to imagined leg paralysis or baseline stimulation without paralysis imagery. These results show that purely imagined bodily constraints can selectively inhibit basic motor corticospinal functions. The results are discussed in the context of motoric embodiment/disembodiment. In this study we investigated whether imagining a specific motor impairment has a physiological effect on motor corticospinal function in healthy participants. We found that imagined hand (but not leg) paralysis reduced TMS induced MEPs of the hand muscle. While previous research mainly focused on excitatory effects of mental imagery, our results point to possible inhibitory effects on motor functions. The results may have relevance in the context of (dis)embodiment research and physiological rehabilitation. [ABSTRACT FROM AUTHOR]

Background/purpose: Paired stimulation can cause neuroplasticity in corticospinal and spinal pathways in subjects with a chronic spinal cord injury (SCI). We aimed to know the effects of different waveforms using paired stimulations with bicycling in subjects with a chronic SCI.Methods: Recruited subjects with an SCI underwent three treatment interventions in random order for 4-20 min followed by 30 min of bicycling (control, repetitive transcranial magnetic stimulation (TMS; rTMS) at 20 Hz with transspinal direct current stimulation (tsDCS), and intermittent theta burst stimulation (iTBS) with tsDCS with a 1-week gap period. A TMS method was employed to record the resting motor threshold (RMT), the 90% values of which was used as the stimulation intensity, and the Hoffman (H)-reflex was measured by stimulating the tibial nerve in the popliteal fossa. The RMT, motor evoked potential (MEP) latency, MEP peak-to-peak amplitude, and H-reflex latency as primary variables and lower extremity motor scale (LEMS) and modified Ashworth spasticity scale (MAS) as secondary variables were analyzed before and after the interventions.Results: The MEP latency, MEP amplitude, and LEMS significantly improved with the rTMS-iTBS/tsDCS or the rTMS-20 Hz/tsDCS (p < 0.050) protocols compared to the control intervention. All other outcome measures, including RMT, H-reflex latency, and MAS score showed some changes but did not fully attain a level of significance.Conclusion: The paired stimulation with rTMS-iTBS/tsDCS was equally effective to produce neuroplastic effect in subjects with chronic SCI compared to the conventional TMS-20 Hz/tsDCS intervention. [ABSTRACT FROM AUTHOR]

Objective: Safe resection of gliomas involving motor pathways in asleepanesthesia requires the combination of brain mapping, to identify and spare essential motor sites, and continuous monitoring of motor-evoked potentials (MEPs), to detect possible vascular damage to the corticospinal tract (CST). MEP monitoring, according to intraoperative neurophysiology societies, is generally recommended by transcranial electrodes (TES), and no clear indications of direct cortical stimulation (DCS) or the preferential use of one of the two techniques based on the clinical context is available. The main aim of the study was to identify the best technique(s) based on different clinical conditions, evaluating the efficacy and prognostic value of both methodologies. Methods: A retrospective series of patients with tumors involving the motor pathways who underwent surgical resection with the aid of brain mapping and combined MEP monitoring via TES and DCS was evaluated. Irreversible MEP amplitude reduction (>50% compared to baseline) was used as an intraoperative warning and correlated to the postoperative motor outcome. Selectivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were computed for both techniques. Results: Four hundred sixty-two patients were retrospectively analyzed, and only 1.9% showed a long-term motor impairment. Both TES and DCS obtained high specificity and NPV for the acute and 1-month motor deficit. Sensitivity was rather low for the acute deficit but excellent considering the 1-month follow-up for both techniques. DCS was extremely reliable in predicting a postoperative motor decline (PPV of 100% and 90% for acute and long-term deficit, respectively). Conversely, TES produced a high number of false-positive results, especially for long-term deficits (65, 87.8% of all warnings) therefore obtaining poor PPV values (18% and 12% for acute and 1-month deficits, respectively). TES false-positive results were significantly associated with parietal tumors and lateral patient positioning. Conclusions: Data support the use of mapping and combined monitoring via TES and DCS. The sole TES monitoring is reliable in most procedures but not in parietal tumors or those requiring lateral positioning. Although no indications are available in international guidelines, DCS should be recommended, particularly for cases approached by a lateral position. [ABSTRACT FROM AUTHOR]

ObjectiveSafe resection of gliomas involving motor pathways in asleep-anesthesia requires the combination of brain mapping, to identify and spare essential motor sites, and continuous monitoring of motor-evoked potentials (MEPs), to detect possible vascular damage to the corticospinal tract (CST). MEP monitoring, according to intraoperative neurophysiology societies, is generally recommended by transcranial electrodes (TES), and no clear indications of direct cortical stimulation (DCS) or the preferential use of one of the two techniques based on the clinical context is available. The main aim of the study was to identify the best technique(s) based on different clinical conditions, evaluating the efficacy and prognostic value of both methodologies.MethodsA retrospective series of patients with tumors involving the motor pathways who underwent surgical resection with the aid of brain mapping and combined MEP monitoring via TES and DCS was evaluated. Irreversible MEP amplitude reduction (>50% compared to baseline) was used as an intraoperative warning and correlated to the postoperative motor outcome. Selectivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were computed for both techniques.ResultsFour hundred sixty-two patients were retrospectively analyzed, and only 1.9% showed a long-term motor impairment. Both TES and DCS obtained high specificity and NPV for the acute and 1-month motor deficit. Sensitivity was rather low for the acute deficit but excellent considering the 1-month follow-up for both techniques. DCS was extremely reliable in predicting a postoperative motor decline (PPV of 100% and 90% for acute and long-term deficit, respectively). Conversely, TES produced a high number of false-positive results, especially for long-term deficits (65, 87.8% of all warnings) therefore obtaining poor PPV values (18% and 12% for acute and 1-month deficits, respectively). TES false-positive results were significantly associated with parietal tumors and lateral patient positioning.ConclusionsData support the use of mapping and combined monitoring via TES and DCS. The sole TES monitoring is reliable in most procedures but not in parietal tumors or those requiring lateral positioning. Although no indications are available in international guidelines, DCS should be recommended, particularly for cases approached by a lateral position.

The representation of muscles in the cortex can be mapped using navigated transcranial magnetic stimulation. The commonly employed measure to quantify the mapping are the center of gravity or the centroid of the region of excitability as well as its size. Determining these measures typically relies only on stimulation points that yield motorevoked potentials (MEPs); stimulations that do not elicit an MEP, i.e., non-MEP points, are ignored entirely. In this study, we show how incorporating non-MEP points may affect the estimates of the size and centroid of the excitable area in eight hand and forearm muscles after mono-phasic single-pulse TMS. We performed test-retest assessments in twenty participants and estimated the reliability of centroids and sizes of the corresponding areas using inter-class correlation coefficients. For most muscles, the reliability turned out good. As expected, removing the non-MEP points significantly decreased area sizes and area weights, suggesting that conventional approaches that do not account for non-MEP points are likely to overestimate the regions of excitability. [ABSTRACT FROM AUTHOR]

Background: Lots of studies have measured motor evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) in anesthetized animals. However, in awake animals, the measurement of TMS-induced MEP is scarce as lack of sufficient restraint. So far, the explicit study of anesthesia effects on corticospinal excitability and repetitive TMS (rTMS) induced modulation is still lacking. This study aimed to: (1) measure TMS-induced MEP in both awake restrained and anesthetized rats, (2) investigate the effect of anesthesia on corticospinal excitability, and (3) on rTMS-induced modulation. Methods: MEP of eighteen rats were measured under both wakefulness and anesthesia using flexible binding and surface electrodes. Peak-to-peak MEP amplitudes, resting motor threshold (RMT) and the slope of stimulus response (SR) were extracted to investigate anesthesia effects on corticospinal excitability. Thereafter, 5 or 10 Hz rTMS was applied with 600 pulses, and the increase in MEP amplitude and the decrease in RMT were used to quantify rTMS-induced modulation. Results: The RMT in the awake condition was 44.6 ± 1.2% maximum output (MO), the peak-to-peak MEP amplitude was 404.6 ± 48.8 μV at 60% MO. Under anesthesia, higher RMT (55.6 ± 2.9% MO), lower peak-to-peak MEP amplitudes (258.6 ± 32.7 μV) and lower slope of SR indicated that the corticospinal excitability was suppressed. Moreover, under anesthesia, high-frequency rTMS still showed significant modulation of corticospinal excitability, but the modulation of MEP peak-to-peak amplitudes was weaker than that under wakefulness. Conclusions: This study measured TMS-induced MEP in both awake and anesthetized rats, and provided explicit evidence for the inhibitory effects of anesthesia on corticospinal excitability and on high-frequency rTMS-induced modulation of MEP. [ABSTRACT FROM AUTHOR]

Background: The effect of a bolus dose of dexmedetomidine on intraoperative neuromonitoring (IONM) parameters during spinal surgeries has been variably reported and remains a debated topic. Methods: A randomized, double-blinded, placebo-controlled study was performed to assess the effect of dexmedetomidine (1 μg/kg in 10 min) followed by a constant infusion rate on IONM during thoracic spinal decompression surgery (TSDS). A total of 165 patients were enrolled and randomized into three groups. One group received propofol- and remifentanil-based total intravenous anesthesia (TIVA) (T group), one group received TIVA combined with dexmedetomidine at a constant infusion rate (0.5 μg kg−1 h−1) (D1 group), and one group received TIVA combined with dexmedetomidine delivered in a loading dose (1 μg kg−1 in 10 min) followed by a constant infusion rate (0.5 μg kg−1 h−1) (D2 group). The IONM data recorded before test drug administration was defined as the baseline value. We aimed at comparing the parameters of IONM. Results: In the D2 group, within-group analysis showed suppressive effects on IONM parameters compared with baseline value after a bolus dose of dexmedetomidine. Furthermore, the D2 group also showed inhibitory effects on IONM recordings compared with both the D1 group and the T group, including a statistically significant decrease in SSEP amplitude and MEP amplitude, and an increase in SSEP latency. No significance was found in IONM parameters between the T group and the D1 group. Conclusion: Dexmedetomidine delivered in a loading dose can significantly inhibit IONM parameters in TSDS. Special attention should be paid to the timing of a bolus dose of dexmedetomidine under IONM. However, dexmedetomidine delivered at a constant speed does not exert inhibitory effects on IONM data. [ABSTRACT FROM AUTHOR]

Background: The effect of a bolus dose of dexmedetomidine on intraoperative neuromonitoring (IONM) parameters during spinal surgeries has been variably reported and remains a debated topic.Methods: A randomized, double-blinded, placebo-controlled study was performed to assess the effect of dexmedetomidine (1 μg/kg in 10 min) followed by a constant infusion rate on IONM during thoracic spinal decompression surgery (TSDS). A total of 165 patients were enrolled and randomized into three groups. One group received propofol- and remifentanil-based total intravenous anesthesia (TIVA) (T group), one group received TIVA combined with dexmedetomidine at a constant infusion rate (0.5 μg kg−1 h−1) (D1 group), and one group received TIVA combined with dexmedetomidine delivered in a loading dose (1 μg kg−1 in 10 min) followed by a constant infusion rate (0.5 μg kg−1 h−1) (D2 group). The IONM data recorded before test drug administration was defined as the baseline value. We aimed at comparing the parameters of IONM.Results: In the D2 group, within-group analysis showed suppressive effects on IONM parameters compared with baseline value after a bolus dose of dexmedetomidine. Furthermore, the D2 group also showed inhibitory effects on IONM recordings compared with both the D1 group and the T group, including a statistically significant decrease in SSEP amplitude and MEP amplitude, and an increase in SSEP latency. No significance was found in IONM parameters between the T group and the D1 group.Conclusion: Dexmedetomidine delivered in a loading dose can significantly inhibit IONM parameters in TSDS. Special attention should be paid to the timing of a bolus dose of dexmedetomidine under IONM. However, dexmedetomidine delivered at a constant speed does not exert inhibitory effects on IONM data.

Objective: The goal of this study is to explore the effect of wrist-ankle acupuncture combined with 5-Hz repetitive transcranial magnetic stimulation (rTMS) on improving spastic state and motor function of children with spastic cerebral palsy by measuring electrophysiological parameters and behaviors. Methods: Twenty-five children with spastic cerebral palsy were enrolled in a single-blind and randomized controlled trial. The control group received 20 sessions of 5-Hz rTMS over the affected hemisphere with 1,000 pulses. The experimental group was given wrist-ankle acupuncture on the basis of the control group. Gross motor function measure (GMFM-66), muscle tension, and electrophysiological parameters of the two groups were assessed at baseline and after intervention. Results: After treatment, the GMFM-66 scores in the same groups were significantly improved (p < 0.001). Besides, the R -value of soleus, gastrocnemius, and hamstring muscle decreased (p < 0.05), and the results showed a trend of shortening MEP latency, increasing amplitude and duration (p < 0.05). Compared to the controlled group, the experimental group displayed more excellent changes in the GMFM-66 scores and motor evoked potential (MEP) latency. The statistical results showed that the increase of GMFM-66 score and the shortening of MEP latency in the experimental group were greater than that in the control group (p < 0.05). However, no significant differences were found in the assessment of muscle tension, amplitude, and duration of MEPs between two groups (p > 0.05). Conclusion: Wrist-ankle acupuncture combined with 5-Hz rTMS is optimal to improve gross motor function and enhance the conductivity of corticospinal tract in children with cerebral palsy but cannot highlight its clinical superiority in improving spasticity. Clinical Trial Registration: [http://www.chictr.org.cn/index.aspx], identifier [chictr2000039495]. [ABSTRACT FROM AUTHOR]

Abstract Background Surgery is usually the treatment of choice for patients with cervical compressive myelopathy (CCM). Motor evoked potential (MEP) has proved to be helpful tool in evaluating intraoperative cervical spinal cord function change of those patients. This study aims to describe and evaluate different MEP baseline phenotypes for predicting MEP changes during CCM surgery. Methods A total of 105 consecutive CCM patients underwent posterior cervical spine decompression were prospectively collected between December 2012 and November 2016. All intraoperative MEP baselines recorded before spinal cord decompression were classified into 5 types (I to V) that were carefully designed according to the different MEP parameters. The postoperative neurologic status of each patient was assessed immediately after surgery. Results The mean intraoperative MEP changes range were 10.2% ± 5.8, 14.7% ± 9.2, 54.8% ± 31.9, 74.1% ± 24.3, and 110% ± 40 in Type I, II, III, IV, and V, respectively. There was a significant correlation of the intraoperative MEP change rate with different MEP baseline phenotypes (r = 0.84, P

BackgroundMajor depressive disorder (MDD) is a severe psychiatric disorder that is associated with various cognitive impairments, including learning and memory deficits. As synaptic plasticity is considered an important mechanism underlying learning and memory, deficits in cortical plasticity might play a role in the pathophysiology of patients with MDD. We used Transcranial Magnetic Stimulation (TMS) to assess inhibitory neurotransmission and cortical plasticity in the motor cortex of MDD patients and controls.MethodsWe measured the cortical silent period (CSP) and short interval cortical inhibition (SICI), as well as intermittent theta-burst stimulation (iTBS), in 9 drug-free MDD inpatients and 18 controls.ResultsThe overall response to the CSP, SICI, and iTBS paradigms was not significantly different between the patient and control groups. iTBS induction resulted in significant potentiation after 20 mins in the control group (t(17) = −2.8, p = 0.01), whereas no potentiation was observed in patients.ConclusionsPotentiation of MEP amplitudes was not observed within the MDD group. No evidence was found for medium-to-large effect size differences in CSP and SICI measures in severely depressed drug-free patients, suggesting that reduced cortical inhibition is unlikely to be a robust correlate of the pathophysiological mechanism in MDD. However, these findings should be interpreted with caution due to the high inter-subject variability and the small sample size.SignificanceThese findings advance our understanding of neurophysiological functioning in drug-free severely depressed inpatients.

Objective: The goal of this study is to explore the effect of wrist-ankle acupuncture combined with 5-Hz repetitive transcranial magnetic stimulation (rTMS) on improving spastic state and motor function of children with spastic cerebral palsy by measuring electrophysiological parameters and behaviors.Methods: Twenty-five children with spastic cerebral palsy were enrolled in a single-blind and randomized controlled trial. The control group received 20 sessions of 5-Hz rTMS over the affected hemisphere with 1,000 pulses. The experimental group was given wrist-ankle acupuncture on the basis of the control group. Gross motor function measure (GMFM-66), muscle tension, and electrophysiological parameters of the two groups were assessed at baseline and after intervention.Results: After treatment, the GMFM-66 scores in the same groups were significantly improved (p < 0.001). Besides, the R-value of soleus, gastrocnemius, and hamstring muscle decreased (p < 0.05), and the results showed a trend of shortening MEP latency, increasing amplitude and duration (p < 0.05). Compared to the controlled group, the experimental group displayed more excellent changes in the GMFM-66 scores and motor evoked potential (MEP) latency. The statistical results showed that the increase of GMFM-66 score and the shortening of MEP latency in the experimental group were greater than that in the control group (p < 0.05). However, no significant differences were found in the assessment of muscle tension, amplitude, and duration of MEPs between two groups (p > 0.05).Conclusion: Wrist-ankle acupuncture combined with 5-Hz rTMS is optimal to improve gross motor function and enhance the conductivity of corticospinal tract in children with cerebral palsy but cannot highlight its clinical superiority in improving spasticity.Clinical Trial Registration: [http://www.chictr.org.cn/index.aspx], identifier [chictr2000039495].

Objective: To investigate whether the changes in the corticospinal excitability contribute to the anticipatory postural adjustments (APAs) in the lower limb muscles when performing the ballistic upper limb movement of the dart throwing. Methods: We examined the primary motor cortex (M1) excitability of the lower limb muscles [tibialis anterior (TA) and soleus (SOL) muscles] during the APA phase by using transcranial magnetic stimulation (TMS) in the healthy volunteers. The surface electromyography (EMG) of anterior deltoid, triceps brachii, biceps brachii, TA, and SOL muscles was recorded and the motor evoked potential (MEP) to TMS was recorded in the TA muscle along with the SOL muscle. TMS at the hotspot of the TA muscle was applied at the timings immediately prior to the TA onset. The kinematic parameters including the three-dimensional motion analysis and center of pressure (COP) during the dart throwing were also assessed. Results: The changes in COP and EMG of the TA muscle occurred preceding the dart throwing, which involved a slight elbow flexion followed by an extension. The correlation analysis revealed that the onset of the TA muscle was related to the COP change and the elbow joint flexion. The MEP amplitude in the TA muscle, but not that in the SOL muscle, significantly increased immediately prior to the EMG burst (100, 50, and 0 ms prior to the TA onset). Conclusion: Our findings demonstrate that the corticospinal excitability of the TA muscle increases prior to the ballistic upper limb movement of the dart throwing, suggesting that the corticospinal pathway contributes to the APA in the lower limb in a muscle-specific manner. [ABSTRACT FROM AUTHOR]

• Two awake, unanesthetized macaque monkeys were used as experimental subjects. • rTMS of either 1 Hz or 10 Hz was applied to the MI in a daily session. • Resting-state ECoGs in the MI and MEPs were recorded before and after rTMS application. • ECoG beta-band power and MEP amplitude significantly decreased after 1-Hz rTMS. • ECoG high-gamma band power and MEP amplitude significantly increased after 10-Hz rTMS. Repetitive transcranial magnetic stimulation (rTMS) is now widely used as a means of neuromodulation, but the details of the mechanisms by which rTMS works remain unclarified. As a step forward to unveiling the neural phenomena occurring underneath the TMS coil, we conducted an electrophysiological study using awake and unanesthetized monkeys with subdural electrocorticogram (ECoG) electrodes implanted over the primary motor cortex (MI). We evaluated the effects of low-frequency (1 Hz) and high-frequency (10 Hz) rTMS on the resting-state ECoG signals in the stimulated MI, as well as the motor evoked potentials (MEPs) in the contralateral hand. Following the 1-Hz rTMS application, the ECoG beta band power and the MEP amplitude were significantly decreased. Following the 10-Hz rTMS application, the ECoG high-gamma power and the MEP amplitude significantly increased. Given that beta and high-gamma activities in the ECoG reflect the synchronous firing and the firing frequency of cell assemblies, respectively, in local neural circuits, these results suggest that low-frequency rTMS inhibits neural activity by desynchronizing the firing activity of local circuits, whereas high-frequency rTMS facilitates neural activity by increasing the firing rate of cell assemblies in the local circuits. [ABSTRACT FROM AUTHOR]

Objective: To investigate whether the changes in the corticospinal excitability contribute to the anticipatory postural adjustments (APAs) in the lower limb muscles when performing the ballistic upper limb movement of the dart throwing.Methods: We examined the primary motor cortex (M1) excitability of the lower limb muscles [tibialis anterior (TA) and soleus (SOL) muscles] during the APA phase by using transcranial magnetic stimulation (TMS) in the healthy volunteers. The surface electromyography (EMG) of anterior deltoid, triceps brachii, biceps brachii, TA, and SOL muscles was recorded and the motor evoked potential (MEP) to TMS was recorded in the TA muscle along with the SOL muscle. TMS at the hotspot of the TA muscle was applied at the timings immediately prior to the TA onset. The kinematic parameters including the three-dimensional motion analysis and center of pressure (COP) during the dart throwing were also assessed.Results: The changes in COP and EMG of the TA muscle occurred preceding the dart throwing, which involved a slight elbow flexion followed by an extension. The correlation analysis revealed that the onset of the TA muscle was related to the COP change and the elbow joint flexion. The MEP amplitude in the TA muscle, but not that in the SOL muscle, significantly increased immediately prior to the EMG burst (100, 50, and 0 ms prior to the TA onset).Conclusion: Our findings demonstrate that the corticospinal excitability of the TA muscle increases prior to the ballistic upper limb movement of the dart throwing, suggesting that the corticospinal pathway contributes to the APA in the lower limb in a muscle-specific manner.

Coupling between cervical and lumbar spinal networks (cervico-lumbar coupling) is vital during human locomotion. Impaired cervico-lumbar coupling after neural injuries or diseases can be reengaged via simultaneous arm and leg cycling training. Sensorimotor circuitry including cervico-lumbar coupling may further be enhanced by non-invasive modulation of spinal circuity using transcutaneous spinal cord stimulation (tSCS). This project aimed to determine the effect of cervical, lumbar, or combined tSCS on spinal reflex (Hoffmann [H-]) and corticospinal (motor evoked potential [MEP]) excitability during a static or cycling cervico-lumbar coupling task. Fourteen neurologically intact study participants were seated in a recumbent leg cycling system. H-reflex and MEP amplitudes were assessed in the left flexor carpi radialis (FCR) muscle during two tasks (Static and Cycling) and four conditions: (1) No tSCS, (2) tSCS applied to the cervical enlargement (Cervical); (3) tSCS applied to the lumbar enlargement (Lumbar); (4) simultaneous cervical and lumbar tSCS (Combined). While cervical tSCS did not alter FCR H-reflex amplitude relative to No tSCS, lumbar tSCS significantly facilitated H-reflex amplitude by 11.1%, and combined cervical and lumbar tSCS significantly enhanced the facilitation to 19.6%. Neither cervical nor lumbar tSCS altered MEP amplitude alone (+4.9 and 1.8% relative to legs static, No tSCS); however, combined tSCS significantly increased MEP amplitude by 19.7% compared to No tSCS. Leg cycling alone significantly suppressed the FCR H-reflex relative to static, No tSCS by 13.6%, while facilitating MEP amplitude by 18.6%. When combined with leg cycling, tSCS was unable to alter excitability for any condition. This indicates that in neurologically intact individuals where interlimb coordination and corticospinal tract are intact, the effect of leg cycling on cervico-lumbar coupling and corticospinal drive was not impacted significantly with the tSCS intensity used. This study demonstrates, for the first time, that tonic activation of spinal cord networks through multiple sites of tSCS provides a facilitation of both spinal reflex and corticospinal pathways. It remains vital to determine if combined tSCS can influence interlimb coupling after neural injury or disease when cervico-lumbar connectivity is impaired.

Coupling between cervical and lumbar spinal networks (cervico-lumbar coupling) is vital during human locomotion. Impaired cervico-lumbar coupling after neural injuries or diseases can be reengaged via simultaneous arm and leg cycling training. Sensorimotor circuitry including cervico-lumbar coupling may further be enhanced by non-invasive modulation of spinal circuity using transcutaneous spinal cord stimulation (tSCS). This project aimed to determine the effect of cervical, lumbar, or combined tSCS on spinal reflex (Hoffmann [H-]) and corticospinal (motor evoked potential [MEP]) excitability during a static or cycling cervico-lumbar coupling task. Fourteen neurologically intact study participants were seated in a recumbent leg cycling system. H-reflex and MEP amplitudes were assessed in the left flexor carpi radialis (FCR) muscle during two tasks (Static and Cycling) and four conditions: (1) No tSCS, (2) tSCS applied to the cervical enlargement (Cervical); (3) tSCS applied to the lumbar enlargement (Lumbar); (4) simultaneous cervical and lumbar tSCS (Combined). While cervical tSCS did not alter FCR H-reflex amplitude relative to No tSCS, lumbar tSCS significantly facilitated H-reflex amplitude by 11.1%, and combined cervical and lumbar tSCS significantly enhanced the facilitation to 19.6%. Neither cervical nor lumbar tSCS altered MEP amplitude alone (+4.9 and 1.8% relative to legs static, No tSCS); however, combined tSCS significantly increased MEP amplitude by 19.7% compared to No tSCS. Leg cycling alone significantly suppressed the FCR H-reflex relative to static, No tSCS by 13.6%, while facilitating MEP amplitude by 18.6%. When combined with leg cycling, tSCS was unable to alter excitability for any condition. This indicates that in neurologically intact individuals where interlimb coordination and corticospinal tract are intact, the effect of leg cycling on cervico-lumbar coupling and corticospinal drive was not impacted significantly with the tSCS intensity used. This study demonstrates, for the first time, that tonic activation of spinal cord networks through multiple sites of tSCS provides a facilitation of both spinal reflex and corticospinal pathways. It remains vital to determine if combined tSCS can influence interlimb coupling after neural injury or disease when cervico-lumbar connectivity is impaired. [ABSTRACT FROM AUTHOR]

Objective: Associative motor cortical plasticity can be non-invasively induced by paired median nerve electric stimulation and transcranial magnetic stimulation (TMS) of the primary motor cortex (M1). This study investigates whether a simultaneous motor reaction of the other hand advances the associative plasticity in M1.Methods: Twenty-four right-handed subjects received conventional paired associative stimulation (PAS) and PAS with simultaneous motor reaction (PASmr) with at least a 1-week interval. The PASmr protocol additionally included left abductor pollicis brevis muscle movement responding to a digital sound. The motor reaction time was individually measured. The M1 excitability was examined by the motor evoked potential (MEP), short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) before and after the PAS protocols.Results: The conventional PAS protocol significantly facilitated MEP and suppressed SICI. A negative correlation between the reaction time and the MEP change, and a positive correlation between the reaction time and the ICF change were found in the PASmr protocol. By subgrouping analysis, we further found significant facilitation of MEP and a reduction of ICF in the subjects with fast reaction times but not in those with slow reaction times.Conclusion: Synchronized motor reaction ipsilateral to the stimulated M1 induces associative M1 motor plasticity through the spike-timing dependent principle. MEP and ICF change could represent this kind of plasticity. The current findings provide a novel insight into designing rehabilitation programs concerning motor function.

Background: Spinal cord infarction (SCI) is a rare disease and its early diagnosis is challenging. Here, we described the clinical features and imaging findings of SCI, and assessed the results of evoked potential (EP) studies to elucidate their diagnostic role in the early stage of SCI.Methods: We retrospectively analyzed 14 patients who had spontaneous SCI. The demographic, neurological, and temporal profiles of the SCI patients were identified. We reviewed the imaging findings and assessed the changes in them over time. To review EP, central motor conduction time (CMCT) and somatosensory evoked potential (SEP) values were obtained. We also enrolled 15 patients with transverse myelitis (TM), and compared the clinical, radiological and electrophysiological features between SCI and TM patients.Results: The ages of the SCI patients ranged from 54 to 73 years. Nine patients (64.3%) showed nadir deficits within 6 h. The most common type of clinical visit was via the emergency center. Nine patients (64.3%) presented with peri-onset focal pain. The median initial modified Rankin scale score was 3. For 9 patients (64.3%), initial T2 imaging findings were negative, but subsequent diffusion weighed imaging (DWI) showed diffusion restriction. Vertebral body infarction was observed in 5 patients (35.7%). EP data were available for 10 SCI patients. All 8 patients who had their CMCT measured showed abnormalities. Among them, motor evoked potentials were not evoked in 6 patients at all. SEP was measured in 10 patients, and 9 of them showed abnormalities; one of them showed no SEP response. For 5 patients, the EP studies were done prior to DWI, and all the patients showed definite abnormalities. The abnormalities in the EP findings of the SCI patients were more profound than those of the TM patients, even though the duration from the onset to the start of the study was much shorter for SCI patients.Conclusion: SCI can be diagnosed based on typical clinical manifestations and appropriate imaging studies. Our study also indicates that immediate sensory and motor EP study can have an adjuvant diagnostic role in the hyperacute stage of SCI, and can improve the accuracy of diagnosis.

Background: Spinal cord infarction (SCI) is a rare disease and its early diagnosis is challenging. Here, we described the clinical features and imaging findings of SCI, and assessed the results of evoked potential (EP) studies to elucidate their diagnostic role in the early stage of SCI. Methods: We retrospectively analyzed 14 patients who had spontaneous SCI. The demographic, neurological, and temporal profiles of the SCI patients were identified. We reviewed the imaging findings and assessed the changes in them over time. To review EP, central motor conduction time (CMCT) and somatosensory evoked potential (SEP) values were obtained. We also enrolled 15 patients with transverse myelitis (TM), and compared the clinical, radiological and electrophysiological features between SCI and TM patients. Results: The ages of the SCI patients ranged from 54 to 73 years. Nine patients (64.3%) showed nadir deficits within 6 h. The most common type of clinical visit was via the emergency center. Nine patients (64.3%) presented with peri-onset focal pain. The median initial modified Rankin scale score was 3. For 9 patients (64.3%), initial T2 imaging findings were negative, but subsequent diffusion weighed imaging (DWI) showed diffusion restriction. Vertebral body infarction was observed in 5 patients (35.7%). EP data were available for 10 SCI patients. All 8 patients who had their CMCT measured showed abnormalities. Among them, motor evoked potentials were not evoked in 6 patients at all. SEP was measured in 10 patients, and 9 of them showed abnormalities; one of them showed no SEP response. For 5 patients, the EP studies were done prior to DWI, and all the patients showed definite abnormalities. The abnormalities in the EP findings of the SCI patients were more profound than those of the TM patients, even though the duration from the onset to the start of the study was much shorter for SCI patients. Conclusion: SCI can be diagnosed based on typical clinical manifestations and appropriate imaging studies. Our study also indicates that immediate sensory and motor EP study can have an adjuvant diagnostic role in the hyperacute stage of SCI, and can improve the accuracy of diagnosis. [ABSTRACT FROM AUTHOR]

Objective : Associative motor cortical plasticity can be non-invasively induced by paired median nerve electric stimulation and transcranial magnetic stimulation (TMS) of the primary motor cortex (M1). This study investigates whether a simultaneous motor reaction of the other hand advances the associative plasticity in M1. Methods : Twenty-four right-handed subjects received conventional paired associative stimulation (PAS) and PAS with simultaneous motor reaction (PASmr) with at least a 1-week interval. The PASmr protocol additionally included left abductor pollicis brevis muscle movement responding to a digital sound. The motor reaction time was individually measured. The M1 excitability was examined by the motor evoked potential (MEP), short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) before and after the PAS protocols. Results : The conventional PAS protocol significantly facilitated MEP and suppressed SICI. A negative correlation between the reaction time and the MEP change, and a positive correlation between the reaction time and the ICF change were found in the PASmr protocol. By subgrouping analysis, we further found significant facilitation of MEP and a reduction of ICF in the subjects with fast reaction times but not in those with slow reaction times. Conclusion : Synchronized motor reaction ipsilateral to the stimulated M1 induces associative M1 motor plasticity through the spike-timing dependent principle. MEP and ICF change could represent this kind of plasticity. The current findings provide a novel insight into designing rehabilitation programs concerning motor function. [ABSTRACT FROM AUTHOR]

Background: Surgery is usually the treatment of choice for patients with cervical compressive myelopathy (CCM). Motor evoked potential (MEP) has proved to be helpful tool in evaluating intraoperative cervical spinal cord function change of those patients. This study aims to describe and evaluate different MEP baseline phenotypes for predicting MEP changes during CCM surgery.Methods: A total of 105 consecutive CCM patients underwent posterior cervical spine decompression were prospectively collected between December 2012 and November 2016. All intraoperative MEP baselines recorded before spinal cord decompression were classified into 5 types (I to V) that were carefully designed according to the different MEP parameters. The postoperative neurologic status of each patient was assessed immediately after surgery.Results: The mean intraoperative MEP changes range were 10.2% ± 5.8, 14.7% ± 9.2, 54.8% ± 31.9, 74.1% ± 24.3, and 110% ± 40 in Type I, II, III, IV, and V, respectively. There was a significant correlation of the intraoperative MEP change rate with different MEP baseline phenotypes (r = 0.84, P < 0.01). Postoperative transient new spinal deficits were found 0/31 case in Type I, 0/21 in Type II, 1/14 in Type III, 2/24 in Type IV, and 4/15 in Type V. No permanent neurological injury was found in our cases series.Conclusions: The MEP baselines categories for predicting intraoperative cervical cord function change is proposed through this work. The more serious the MEP baseline abnormality, the higher the probability of intraoperative MEP changes, which is beneficial to early warning for the cervical cord injury. [ABSTRACT FROM AUTHOR]

Alpha oscillations (8-14 Hz) are assumed to gate information flow in the brain by means of pulsed inhibition; that is, the phasic suppression of cortical excitability and information processing once per alpha cycle, resulting in stronger net suppression for larger alpha amplitudes due to the assumed amplitude asymmetry of the oscillation. While there is evidence for this hypothesis regarding occipital alpha oscillations, it is less clear for the central sensorimotor μ-alpha rhythm. Probing corticospinal excitability via transcranial magnetic stimulation (TMS) of the primary motor cortex and the measurement of motor evoked potentials (MEPs), we have previously demonstrated that corticospinal excitability is modulated by both amplitude and phase of the sensorimotor μ-alpha rhythm. However, the direction of this modulation, its proposed asymmetry, and its underlying mechanisms remained unclear. We therefore used real-time EEG-triggered single- and paired-pulse TMS in healthy humans of both sexes to assess corticospinal excitability and GABA-A-receptor mediated short-latency intracortical inhibition (SICI) at rest during spontaneous high amplitude μ-alpha waves at different phase angles (peaks, troughs, rising and falling flanks) and compared them to periods of low amplitude (desynchronized) μ-alpha. MEP amplitude was facilitated during troughs and rising flanks, but no phasic suppression was observed at any time, nor any modulation of SICI. These results are best compatible with sensorimotor μ-alpha reflecting asymmetric pulsed facilitation but not pulsed inhibition of motor cortical excitability. The asymmetric excitability with respect to rising and falling flanks of the μ-alpha cycle further reveals that voltage differences alone cannot explain the impact of phase. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reliability of daily applied 1 and 20 Hz rTMS protocols is low to moderate. • Present data questions that low frequency rTMS inhibits and high frequency rTMS facilitates. • Further research is needed to enhance reliability in non-invasive brain stimulation. The aim of this study was to investigate the reliability of low-frequency and high-frequency repetitive transcranial magnetic stimulation (rTMS) on healthy individuals over the motor cortex. A secondary outcome was the assessment if low-frequency rTMS results in inhibition and high-frequency rTMS results in facilitation. In this experiment, 30 healthy participants received on four consecutive days one session each with application of 1 Hz or 20 Hz rTMS over the left motor cortex. 1 Hz and 20 Hz were applied in alternating order, whereby the starting frequency was randomized. Motor evoked potentials (MEPs) were measured before and after each session. Reliability measures were intraclass and Pearson's correlation coefficient (ICC and r). ICCs and r values were low to moderate. Notably, within subgroups of less confounded measures, we found good r values for 20 Hz rTMS. The group-level analysis did not demonstrate a clear low-frequency inhibition and high-frequency facilitation pattern. At the single-subject level, only one participant exhibited significant changes consistent with the expected pattern, with concurrent decreases in MEPs following 1 Hz sessions and increases following 20 Hz sessions. The investigated neuromodulatory protocols show low to moderate reliability. Results are questioning the low-frequency inhibition and high-frequency facilitation pattern. Methodological improvements for the usage of rTMS are necessary to increase validity and reliability of non-invasive brain stimulation. [ABSTRACT FROM AUTHOR]

Motor-evoked potentials (MEPs) are widely used for biomarkers and dose individualization in transcranial stimulation. The large variability of MEPs requires sophisticated methods of analysis to extract information fast and correctly. Development and testing of such methods relies on the availability for realistic models of MEP generation, which are presently lacking. This paper presents a statistical model that can simulate long sequences of individualized MEP amplitude data with properties matching experimental observations. The MEP model includes three sources of trial-to-trial variability: excitability fluctuations, variability in the neural and muscular pathways, and physiological and measurement noise. It also generates virtual human subject data from statistics of population variability. All parameters are extracted as statistical distributions from experimental data from the literature. The model exhibits previously described features, such as stimulus-intensity-dependent MEP amplitude distributions, including bimodal ones. The model can generate long sequences of test data for individual subjects with specified parameters or for subjects from a virtual population. The presented MEP model is the most detailed to date and can be used for the development and implementation of dosing and biomarker estimation algorithms for transcranial stimulation. [ABSTRACT FROM AUTHOR]

Application of transcranial magnetic stimulation (TMS) is expanding with many studies applying adaptive threshold hunting to determine a motor threshold (MT). In addition to being a measure of corticospinal excitability, the MT is used as a baseline stimulation intensity (SI) to which following investigative or modulatory SIs are referenced to. Currently available tools for determining MTs include system-integrated tools and third-party stand-alone software. System-integrated MT-tools are still rarely available and the stand-alone software usually demand a separate computer, and hence possess additional space-requirements. I introduce and validate a free Android-based mobile application (“ATH-tool”) for adaptive threshold hunting of the MT. The objective is to allow for a simple and validated recording of MTs with sharing capabilities for logs. For comparison, I applied Motor Threshold Assessment Tool 2.0, to compare the MT-values determined with the new application, as it applies closely the same routine. Computational validation with known true threshold values confirmed that the new application captured the true MT at high precision (error ≤ 0.9%). Previously published data on motor evoked potentials (MEPs) were used to simulate realistic response occurrence by considering experimental data from 15 healthy subjects at different stimulation intensities. The MTs of the different methods agreed well (ICC ≥ 0.971, ${p} < 0.001$). There was no significant difference between the MTs determined with the different methods ($p \ge0.151$). The novel mobile application should make it easier for researchers and clinicians to determine MTs and log the results. [ABSTRACT FROM AUTHOR]

Highlights • Motor evoked potential (MEP) deterioration duration can be used to predict postoperative motor deficits. • Patients with MEP deterioration duration ≥13 min have a higher risk of postoperative motor deficits. • MEP deterioration duration is not associated with postoperative CT abnormalities. Abstract Objective The study aimed to investigate the predictive value of motor evoked potential (MEP) deterioration duration for postoperative motor deficits in patients undergoing intracranial aneurysm surgery. Methods Data from 587 patients were reviewed and 92 patients with MEP deterioration were enrolled. MEP deterioration duration was compared between patients with and without postoperative motor deficits. Receiver operating characteristic (ROC) curve analysis was performed to define the threshold value for predicting postoperative motor deficit risk. Additionally, the association between MEP deterioration duration and postoperative CT findings was explored. Results Patients with postoperative motor deficits had a significantly longer MEP deterioration duration (p < 0.01). An MEP deterioration duration greater than or equal to 13 min was identified as an independent predictor of immediate (p < 0.01), short-term (p < 0.01), and long-term postoperative motor deficits (p < 0.05). There was no significant association between MEP deterioration duration and new CT abnormalities. Conclusion MEP deterioration duration could be used for predicting intracranial aneurysm surgical outcome. Significance The study first proposed a threshold value of MEP deterioration duration (13 min) for predicting the risk of postoperative motor deficits in patients undergoing intracranial aneurysm surgery. [ABSTRACT FROM AUTHOR]

Movement complexity is known to increase reaction time (RT). More recently, transcranial magnetic stimulation (TMS) of the motor cortex has revealed that movement complexity can alter corticospinal excitability. However, the impact of a sequential addition of movement components on corticospinal excitability during the preparatory phase of a simple RT task is unknown. Thus, the purpose of this study was to examine how motor evoked potentials (MEPs) in the premotor period were affected by the complexity of a movement in a simple RT paradigm. Participants (n = 12) completed ballistic movements with their dominant arm, in which they directed a robotic handle to one, two or three targets (32 trials per condition). TMS was delivered prior to movement at 0, 70, 80 or 90% of each participant's mean premotor RT, at the stimulator intensity which yielded a triceps brachii MEP of ~ 10% the maximal M-wave. As expected, premotor RT slowed with increasing task complexity. Although background electromyographic activity (EMG) of the triceps brachii during the preparation phase did not differ among conditions, MEP amplitude increased with movement complexity (i.e., MEPs were greater for the 2- and 3-movement conditions, compared to the 1-movement condition at 80% of premotor RT). We propose the lengthened RTs could be due in part to less suppression of particular motor circuits, while other circuitry is responsible for the increased MEPs. This study demonstrates that, prior to movement, corticospinal excitability increases as a consequence of movement complexity. [ABSTRACT FROM AUTHOR]

Introduction: The purpose was to investigate the age effects on central versus peripheral sources of strength, fatigue, and central neural excitabilities.Methods: 42 healthy subjects were recruited as young group (23.73 ± 2.15 years; n = 26) and middle-aged group (57.25 ± 4.57 years; n = 16). Maximum voluntary contraction force (MVC), voluntary activation level (VA), and twitch force of quadriceps were evaluated to represent general, central, and peripheral strengths. Central and peripheral fatigue indexes were evaluated using femoral nerve electrical stimulation. Cortical excitabilities were evaluated using transcranial magnetic stimulation (TMS).Results: The middle-aged group had lower MVC and twitch force of quadriceps, but not VA, than young group. No between group differences were found in fatigue indexes. The cortical excitability in middle-aged group was different from young group in paired TMS with inter-stimulus interval of 7 ms.Conclusion: The age-related strength loss at early stage was primarily caused by peripheral muscular strength. The deviation of central neural excitability can be detected but the activation level was not impaired in middle-age adults. [ABSTRACT FROM AUTHOR]

The conditioning of cortical excitability by transcranial magnetic stimulation (TMS) has become a valuable technique to promote recovery of motor function after stroke. As TMS is not used in all patients, we investigated the hypothesis that peripheral stimulation may have an adjustment effect on motor cortical excitability. Our experimental paradigm was divided into three phases. In the first phase, TMS was delivered to the left or right primary motor cortex to induce a motor evoked potential (MEP) from the contralateral first dorsal interosseous muscle. The measured MEPs in this phase were used to evaluate the effect of peripheral stimulation. In the second phase, 1 Hz magnetic stimulation was applied over the contralateral or ipsilateral forearm for motor cortex as peripheral stimulation. In the third phase, the MEP was evoked by TMS and recorded using the same setting as the first phase. We found that a decrease in MEP amplitude was observed in the left motor cortex following peripheral stimulation over the right forearm. By contrast, the MEP amplitude was not altered in the right motor cortex by peripheral stimulation over the left forearm. An increase in MEP amplitude was observed in the ipsilateral motor cortex induced by peripheral stimulation over the left or right forearm. We also found that by changing the MEP amplitude, the motor cortex excitability varied according to magnetic stimulation of the forearm. These data suggest that peripheral stimulation may have an adjustment effect on motor cortical excitability, via changes in the stimulus site. [ABSTRACT FROM AUTHOR]

Background Alpha (8–14 Hz) oscillatory power is linked to cortical excitability and corresponding modulations of sensory evoked potentials and perceptual detection performance. In somatosensory cortex (S1), negative linear and inverted U-shape relationships exist, whereas its effect on the primary motor cortex (M1) is hardly known. Objective We used real-time EEG-triggered transcranial magnetic stimulation (TMS) of M1 to characterize the relationship between spontaneous sensorimotor mu-alpha power fluctuations at rest and corticospinal excitability. Methods In 16 subjects, mu-alpha power was continuously monitored over the left sensorimotor cortex, and each 10%-percentile bin of the individual mu-alpha power distribution was repeatedly targeted in pseudorandomized order by single-pulse TMS of left M1, measuring motor evoked potentials (MEP) in the contralateral hand. Results We found a weak positive relationship between mu-alpha power and MEP amplitude. Conclusion Sensorimotor mu-alpha power may reflect a net facilitation or disinhibition of M1, possibly resulting from mu-alpha based suppression of excitatory and inhibitory input from S1. [ABSTRACT FROM AUTHOR]

We characterized the short-interval intracortical facilitation (SICF) via modulation of transcranial magnetic stimulation (TMS) induced motor evoked potentials (MEPs) using paired-pulse stimulation, and analyzed the interactions with known SICF I-wave behavior. The objective was to optimize individual SICF to enhance TMS effects for motor mapping and therapeutic stimulations. We applied navigated TMS in nine healthy volunteers to study SICF. MEPs were measured for baseline using single-pulse TMS, and subsequently, paired-pulse TMS was applied to study SICF. The interstimulus interval (ISI) between the paired pulses was varied between 1.2 and 4.3 ms at 0.1 ms intervals. Ten MEPs were measured from three muscles (FDI, APB, and ADM) in the dominant hand of the volunteer. We then fitted a 3-peak Gaussian model to the individual paired-pulse MEP vs. ISI curves to characterize each peak by latency, amplitude, and width. Individual SICF I-wave interaction characteristics were successfully determined. The average peak latencies were 1.36 ms (I1-wave), 2.80 ms (I2-wave), and 4.29ms (I3-wave) for the targeted FDI muscle. The peak amplitudes differed depending on the muscle (${p} = {0.001}$), with ADM muscle exhibiting greatest SICF effect, but no significant difference between the three peaks. In addition, the peak widths differed between all muscles (${p} < {0.001}$), second peak being the widest. In conclusion, the individual SICF I-wave interaction characteristics were successfully determined revealing significant differences in peak features. This could enable application of SICF for enhancement of TMS effects in therapy, cortical mapping, and basic neuroscience applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In many cases, neural signals detected under the same external experimental conditions significantly change from trial to trial. The variability phenomenon, which complicates extraction of reproducible results and is ignored in many studies by averaging, has attracted attention of researchers in recent years. In this paper, we classify possible types of variability based on its functional significance and describe features of each type. We describe the key adaptive significance of variability at the neural network level and the degeneracy phenomenon that may be important for learning processes in connection with the principle of neuronal group selection.

Various degrees of neural reorganization may occur in affected and unaffected hemispheres in the early phase after stroke and several months later. Recent literature suggests to apply a stratification based on lesion location and to consider patients with cortico-subcortical and subcortical strokes separately: different lesion location may also influence therapeutic response. In this study we used a longitudinal approach to perform TMS assessment (Motor Evoked Potentials, MEP, and Silent Period, SP) and clinical evaluations (Barthel Index, Fugl-Meyer Assessment for upper limb motor function and Wolf Motor Function Test) in 10 cortical-subcortical and 10 subcortical ischemic stroke patients. Evaluations were performed in a window between 10 and 45 days (t0) and at 3 months after the acute event (t1). Our main finding is that 3 months after the acute event patients affected by subcortical stroke presented a reduction in contralateral SP duration in the unaffected hemisphere; this trend is related to clinical improvement of upper limb motor function. In conclusion, SP proved to be a valid parameter to characterize cortical reorganization patterns in stroke survivors and provided useful information about motor recovery within three months in subcortical patients.