Intensity Of Magnetic Stimulation Research Articles

ID: 325336 Examining the Impact of Transcranial Magnetic Stimulation Intensity on Instantaneous Communication with dynamical EEG analysis

ID: 325336 Examining the Impact of Transcranial Magnetic Stimulation Intensity on Instantaneous Communication with dynamical EEG analysis

The consequences of the new European reclassification of non-invasive brain stimulation devices and the medical device regulations pose an existential threat to research and treatment: An invited opinion paper

A significant amount of European basic and clinical neuroscience research includes the use of transcranial magnetic stimulation (TMS) and low intensity transcranial electrical stimulation (tES), mainly transcranial direct current stimulation (tDCS). Two recent changes in the EU regulations, the introduction of the Medical Device Regulation (MDR) (2017/745) and the Annex XVI have caused significant problems and confusions in the brain stimulation field. The negative consequences of the MDR for non-invasive brain stimulation (NIBS) have been largely overlooked and until today, have not been consequently addressed by National Competent Authorities, local ethical committees, politicians and by the scientific communities. In addition, a rushed bureaucratic decision led to seemingly wrong classification of NIBS products without an intended medical purpose into the same risk group III as invasive stimulators.Overregulation is detrimental for any research and for future developments, therefore researchers, clinicians, industry, patient representatives and an ethicist were invited to contribute to this document with the aim of starting a constructive dialogue and enacting positive changes in the regulatory environment.

Effect of high-frequency (5Hz) rTMS stimulating left DLPFC combined with galantamine on cognitive impairment after ischemic stroke and serum homocysteine and neuron-specific enolase.

To investigate the efficacy of high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) combined with galantamine in patients with cognitive impairment after stroke and its effect on serum homocysteine (Hcy) and neuron-specific enolase (NSE) levels. A total of 90 patients with cognitive impairment after the first ischemic stroke were enrolled. They were randomly divided into rTMS+ cognitive rehabilitation group, Galantamine + cognitive rehabilitation group, and rTMS+ Galantamine + cognitive rehabilitation group. All groups received routine medical treatment and limb rehabilitation treatment. The rTMS stimulation site was the left dorsolateral prefrontal cortex (left DLPFC), the magnetic stimulation frequency was 5 Hz, the magnetic stimulation intensity was 80% of the motor threshold level, and 3,000 pulses were given every day. The Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Fugl-Meyer scale, and modified Barthel index, as well as rehabilitation scale and serum NSE and Hcy were evaluated before and after treatment (after 4 weeks). After 4 weeks of treatment, the scores of MMSE, MoCa scale, Fugl-Meyer scale, and modified Barthel index in the three groups were significantly higher than those before treatment (all p < 0.05), while the serum NSE and Hcy levels of the three groups were decreased. rTMS+ Galantamine + cognitive rehabilitation group had higher scale scores, and the difference between the three groups was statistically significant compared with the other two groups (all p < 0.05). Cognitive rehabilitation combined with HF-rTMS and galantamine could improve the cognitive function of patients to the greatest extent, promote the recovery of physical activity, improve the self-care ability of daily life, and effectively reduce the serum HCY and NSE levels in patients with cognitive impairment after stroke. No randomized controlled trials of similar combination treatments have been reported. The better therapeutic effect may be related to the fact that galantamine combined with repetitive transcranial magnetism can activate the brain cholinergic system more extensively, promote brain neural remodeling through long-term potentiation and inhibit local neuroinflammatory responses in brain injury.

Effects of Different Intensities of Repetitive Peripheral Magnetic Stimulation on Spinal Reciprocal Inhibition in Healthy Persons.

This study aimed to assess the effect of the spinal circuit of repetitive magnetic stimulation (rPMS) on the soleus muscle among healthy subjects. Nineteen healthy adults were included in this study. Intermittent rPMS was applied to the left soleus muscle for 20 minutes. We applied different intensity rPMS (high-intensity, low-intensity, and non-stimulation) in different three days. RI (reciprocal inhibition) from the tibialis anterior to the soleus muscle with an inter-stimulus interval (ISI) of 2ms and 20ms was assessed before, immediately after and 30 minutes at each session. Two factor repeated measure ANOVA test showed a significant interaction (F2,33 = 9.688, p < 0.001) between tasks and time in the RI ratio 2ms. Post-hoc analysis showed that RI ratio 2ms significantly differed from those immediately after, and 30 min after high-intensity rPMS (p = 0.001 and p = 0.003, respectively). A significant difference was observed between high-intensity rPMS and non-stimulation immediately after the stimulation (p = 0.003). However, no significant difference was found in the RI ratio 20ms between all the intensities (p > 0.05). This study demonstrates that high-intensity rPMS can effectively modulate spinal circuits, as evidenced by the decreased RI in healthy individuals. This suggests the potential use of rPMS as a therapeutic intervention for patients with muscle weakness. Disinhibition of the RI may lead to a more effective contraction of the target muscle. This effect could be expected to strengthen the muscles and alleviate paralysis, making it a promising avenue for future research and clinical applications in the field of rehabilitation. Further investigation is warranted to explore the precise mechanisms underlying the observed effects and to optimize the parameters of rPMS for specific clinical populations.

A dose-response characterization of transcranial magnetic stimulation intensity and evoked potential amplitude in the dorsolateral prefrontal cortex

By combining transcranial magnetic stimulation (TMS) with electroencephalography, human cortical circuits can be directly interrogated. The resulting electrical trace contains TMS-evoked potential (TEP) components, and it is not known whether the amplitudes of these components are stimulus intensity dependent. We examined this in the left dorsolateral prefrontal cortex in nineteen healthy adult participants and extracted TEP amplitudes for the N40, P60, N120, and P200 components at 110%, 120%, and 130% of resting motor threshold (RMT). To probe plasticity of putative stimulus intensity dose-response relationships, this was repeated after participants received intermittent theta burst stimulation (iTBS; 600 pulses, 80% RMT). The amplitude of the N120 and P200 components exhibited a stimulus intensity dose-response relationship, however the N40 and P60 components did not. After iTBS, the N40 and P60 components continued to exhibit a lack of stimulus intensity dose-dependency, and the P200 dose-response was unchanged. In the N120 component, however, we saw evidence of change within the stimulus intensity dose-dependent relationship characterized by a decrease in absolute peak amplitudes at lower stimulus intensities. These data suggest that TEP components have heterogeneous dose-response relationships, with implications for standardizing and harmonizing methods across experiments. Moreover, the selective modification of the N120 dose-response relationship may provide a novel marker for iTBS plasticity in health and disease.

Disrupted synaptic homeostasis and partial occlusion of associative long-term potentiation in the human cortex during social isolation

Social isolation often occurs in the military mission of soldiers but has increased in the general population since the COVID-19 epidemic. Overall synaptic homeostasis along with associative plasticity for the activity-dependent refinement of transmission across single synapses represent basic neural network function and adaptive behavior mechanisms. Here, we use electrophysiological and behavioral indices to non-invasively study the net synaptic strength and long-term potentiation (LTP)-like plasticity of humans in social isolation environments. The theta activity of electroencephalography (EEG) signals and transcranial magnetic stimulation (TMS) intensity to elicit a predefined amplitude of motor-evoked potential (MEP) demonstrate the disrupted synaptic homeostasis in the human cortex during social isolation. Furthermore, the induced MEP change by paired associative stimulation (PAS) demonstrates the partial occlusion of LTP-like plasticity, further behavior performances in a word-pair task are also identified as a potential index. Our study indicates that social isolation disrupts synaptic homeostasis and occludes associative LTP-like plasticity in the human cortex, decreasing behavior performance related to declarative memory.

Simulation design and experimental study of magnetic stimulation coil for robot pigeon

To explore the feasibility of applying magnetic stimulation technology to the movement control of animal robots, the influence of coil radius, number of turns and other factors on the intensity, depth and focus of magnetic stimulation was simulated and analyzed for robot pigeons. The coil design scheme was proposed. The coil was placed on the head and one of the legs of the pigeon, and the leg electromyography (EMG) was recorded when magnetic stimulation was performed. Results showed that the EMG was significantly strengthened during magnetic stimulation. With the reduction of the output frequency of the magnetic stimulation system, the output current was increased and the EMG was enhanced accordingly. Compared with the brain magnetic stimulation, sciatic nerve stimulation produced a more significant EMG enhancement response. This indicated that the magnetic stimulation system could effectively modulate the functions of brain and peripheral nerves by driving the coil. This study provides theoretical and experimental guidance for the subsequent optimization and improvement of practical coils, and lays a preliminary theoretical and experimental foundation for the implementation of magnetic stimulation motion control of animal robots.

Activation of human spinal locomotor circuitry using transvertebral magnetic stimulation.

Transvertebral magnetic stimulation (TVMS) of the human lumbar spinal cord can evoke bilateral rhythmic leg movements, as in walking, supposedly through the activation of spinal locomotor neural circuitry. However, an appropriate stimulus intensity that can effectively drive the human spinal locomotor circuitry to evoke walking-like movements has not been determined. To address this issue, TVMS was delivered over an intervertebral space of the lumbar cord (L1–L3) at different stimulus intensities (10–70% of maximum stimulator output) in healthy human adults. In a stimulus intensity-dependent manner, TVMS evoked two major patterns of rhythmic leg movements in which the left-right movement cycles were coordinated with different phase relationships: hopping-like movements, in which both legs moved in the same direction in phase, and walking-like movements, in which both legs moved alternatively in anti-phase; uncategorized movements were also observed which could not be categorized as either movement type. Even at the same stimulation site, the stimulus-evoked rhythmic movements changed from hopping-like movements to walking-like movements as stimulus intensity was increased. Different leg muscle activation patterns were engaged in the induction of the hopping- and walking-like movements. The magnitude of the evoked hopping- and walking-like movements was positively correlated with stimulus intensity. The human spinal neural circuitry required a higher intensity of magnetic stimulation to produce walking-like leg movements than to produce hopping-like movements. These results suggest that TVMS activates distinct neural modules in the human spinal cord to generate hopping- and walking-like movements.

Investigation of how stimulation intensity of rTMS affects magneto permeabilization of the Blood–Brain Barrier (BBB)

ABSTRACT The present study aimed to assess the effect of the rTMS (repetitive Transcranial Magnetic Stimulation) intensity on the permeability of the BBB for brain-targeted drug delivery. For this purpose, different rTMS intensities including 70%, 100%, and 130% of Resting Motor Threshold (RMT) assessed in three groups of rats (three groups of 5 rats). Stimulation applied over the right hemisphere of the animals. The first phase of the study was composed of intravenous administration of Evans Blue Dye (EBD), rTMS stimulation and EBD uptake measurement in both brain hemispheres. The second examination was included rTMS stimulation, injection of the MRI Contrast Agent (CA), and signal intensity measurement in post-contrast images. Each exam also included five rats in a sham group. Thus, the total of 40 male Wistar rats enrolled in this study. There was no significant difference in the amount of EBD accumulated between the right hemisphere of the brain in the sham group and the group with 70% RMT magnetic stimulation, while this figure was significantly higher than the sham group for both 100 and 130% RMT groups. There was also a significant difference in this index between 100 and 130% groups. All of the results from the first phase of the study were consistent with the second assessment representing an upward trend of induced permeability by rising rTMS intensity. The results of this study imply that to cause an effective temporary disruption in the BBB the intensity of 100% RMT or above should be used for stimulation.

Modification in Pittsburgh Sleep Quality Index after low intensity transcranial magnetic stimulation in patients with fibromyalgia

Fibromyalgia is a disease of unknown origin in which sleep involvement is very prevalent, and one of the main symptoms, even as prevalent as pain. In fact, one condition has been linked to the other, and the two may feedback on each other. We investigated what happens if by applying low-field magnetic stimulation in patients with fibromyalgia, it could improve sleep variables, and if this would be related to an improvement in the pain of the patients. We compared the results of a group of female patients with fibromyalgia, who underwent treatment for 6 weeks, with another group of patients with similar characteristics, who were not treated. The results were also compared with a group of healthy women, who served as a second control group. The Pittsburgh sleep scale was used as a sleep scale and a global clinical scale was used to assess general state. A significant improvement was observed in the different items of the sleep scale applied, from the four weeks of treatment, being even more evident at the end of treatment at six weeks. A total of 82% of patients improved at the end of treatment. There was a correlation of this improvement with the overall pain situation of the patients. In addition, there was a trend towards equal sleep outcomes between treated patients and healthy subjects. Treatment with low intensity magnetic stimulation could improve the sleep of fibromyalgia patients, as well as their overall clinical situation, and both processes could be interrelated.

Dorsolateral prefrontal cortex excitability assessed using TMS‐EEG and its relationship with neuropsychiatric symptoms in Alzheimer’s dementia

AbstractBackgroundNeuropsychiatric symptoms (NPS) are common in patients with Alzheimer’s Dementia (AD) and cause substantial distress to patients and caregivers. Mechanisms underlying NPS are not well known. Studies have found increased cortical excitability in patients with AD. Studies in other neuropsychiatric disorders have found increased cortical excitability in association with NPS. We hypothesized that cortical excitability will be negatively associated with cognition and positively associated with NPS in AD.MethodThis cross‐sectional study included participants diagnosed with probable AD using the NIA‐AA core clinical criteria. Cognition was assessed using Montreal Cognitive Assessment (MoCA) and NPS were assessed using the Neuropsychiatric Inventory‐Questionnaire (NPI‐Q). NPIQ agitation‐hyperactivity domain scores were calculated by combining scores on agitation, aggression, anxiety, disinhibition and irritability domains. Motor threshold and Transcranial Magnetic Stimulation (TMS) intensity sufficient to induce 1 millivolt (mV) peak to peak motor evoked potential were calculated as per established methods. TMS at the 1mV intensity was applied to the dorsolateral prefrontal cortex (DLPFC) at a frequency of 0.1 Hz. Electroencephalography was collected during TMS. Cortical excitability was assessed using rectified area under the curve (AUC) for TMS‐evoked potential (TEP) during early (25‐80 ms) and late phases (80 – 200 ms). Individual TEP peak amplitudes were also calculated.ResultThe study included 25 participants (female = 17, Mean (SD) age = 74.3(7.1) Years, Mean (SD) MoCA score = 17.5 (4.6)). There was a negative correlation between MoCA and the TEP early AUC at the DLPFC site of stimulation (Spearman’s rs = ‐ 0.589, n = 24, p = 0.002). In contrast there was a positive correlation between NPI‐Q agitation ‐ hyperactivity domain scores and the TEP early AUC (Spearman’s rs = 0.422, n = 24, p = 0.04). There was also a positive correlation between total NPIQ and early TEP (P30) amplitude.ConclusionCortical excitability in the DLPFC is inversely associated with cognition and positively associated with NPS in AD. Specifically, increased excitability found during the early TEP duration suggests potential role of aberrant glutamatergic transmission and overall gamma amino butyric acid and glutamate imbalance. These findings may have important implications for developing treatment interventions targeting cortical excitability in AD.

Ultrafast ultrasound coupled with cervical magnetic stimulation for non-invasive and non-volitional assessment of diaphragm contractility.

Twitch transdiaphragmatic pressure elicited by cervical magnetic stimulation of the phrenic nerves is a fully non-volitional method for assessing diaphragm contractility in humans, yet it requires invasive procedures such as oesophageal and gastric catheter balloons. Ultrafast ultrasound enables a very high frame rate allowing the capture of transient events, such as muscle contraction elicited by nerve stimulation (twitch). Whether indices derived from ultrafast ultrasound can be used as an alternative to the invasive measurement of twitch transdiaphragmatic pressure is unknown. Our findings demonstrate that maximal diaphragm tissue velocity assessed using ultrafast ultrasound following cervical magnetic stimulation is reliable, sensitive to change in cervical magnetic stimulation intensity, and correlates to twitch transdiaphragmatic pressure. This approach provides a novel fully non-invasive and non-volitional tool for the assessment of diaphragm contractility in humans. Measuring twitch transdiaphragmatic pressure (Pdi,tw ) elicited by cervical magnetic stimulation (CMS) is considered as a reference method for the standardized evaluation of diaphragm function. Yet, the measurement of Pdi requires invasive oesophageal and gastric catheter-balloons. Ultrafast ultrasound is a non-invasive imaging technique enabling frame rates high enough to capture transient events such as evoked muscle contractions. This study investigated relationships between indices derived from ultrafast ultrasound and Pdi,tw , and how these indices might be used to estimate Pdi,tw . CMS was performed in 13healthy volunteers from 30% to 100% of maximal stimulator intensity in units of 10% in a randomized order. Pdi,tw was measured and the right hemidiaphragm was imaged using a custom ultrafast ultrasound sequence with 1kHz framerate. Maximal diaphragm axial velocity (Vdi ,max ) and diaphragm thickening fraction (TFdi,tw ) were computed. Intra-session reliability was assessed. Repeated-measures correlation (R) and Spearman correlation coefficients (ρ) were used to assess relationships between variables. Intra-session reliability was strong for Pdi,tw and Vdi,max and moderate for TFdi,tw . Vdi,max correlated with Pdi,tw in all subjects (0.64<ρ<1.00, R=0.75; all P < 0.05). TFdi,tw correlated with Pdi,tw in eight subjects only (0.85<ρ<0.93, R=0.69; all P<0.05). Coupling ultrafast ultrasound and CMS shows promise for the non-invasive and fully non-volitional assessment of diaphragm contractility. This approach opens up the prospect of both diagnosis and follow-up of diaphragm contractility in clinical populations.

Fatigue-induced changes in short-interval intracortical inhibition and the silent period with stimulus intensities evoking maximal versus submaximal responses.

During fatiguing exercise, previous studies have employed transcranial magnetic stimulation (TMS) paradigms eliciting either maximal or submaximal short-interval intracortical inhibition (SICI) and silent period (SP) durations. However, the effect of using either approach on the change in these variables with fatigue is unknown. This study examined the effects of using conditioning stimulus (CS, experiment A) and single-pulse TMS intensities (experiment B) that elicit maximal and submaximal SICI and SP duration (MaxSICI vs. SubmaxSICI in experiment A, MaxSP vs. SubmaxSP in experiment B) on the change in these measures with fatigue. In both experiments, participants performed a 10-min sustained isometric knee-extension contraction at a constant level of EMG, with measurements taken with maximal and submaximal intensities at baseline and every 2.5 min throughout the task. Immediately after the 10-min contraction (i.e., without recovery), responses were also measured at the same absolute force level as at baseline. In experiment A, no change in SICI was observed with either CS intensity throughout the EMG task (P > 0.05). However, an 18% decrease in SICI (i.e., less inhibition) was observed at the same absolute force only with the MaxSICI CS intensity (P < 0.01), with no change in SubmaxSICI (P = 0.72). In experiment B, the magnitude of increase in SP with fatigue was similar for both stimulus intensities (stimulus × time interaction: P = 0.44). These results suggest that CS intensities eliciting maximum SICI are more sensitive in detecting fatigue-induced reductions in SICI, whereas increases in SP are detectable with TMS intensities evoking maximal or submaximal SPs.NEW & NOTEWORTHY This study compared the change in silent period (SP) and short-interval intracortical inhibition (SICI) with conditioning stimulus and single-pulse transcranial magnetic stimulation (TMS) intensities (for SICI and SP, respectively) eliciting maximal and submaximal SICI and SP during fatiguing exercise. The results showed that changes in SICI were only detectable with intensities evoking maximal responses, with no difference between intensities for SP. These findings highlight the importance of maximizing SICI with appropriate intensities before measuring SICI during fatiguing exercise.

Guidelines for TMS/tES clinical services and research through the COVID-19 pandemic

BackgroundThe COVID-19 pandemic has broadly disrupted biomedical treatment and research including non-invasive brain stimulation (NIBS). Moreover, the rapid onset of societal disruption and evolving regulatory restrictions may not have allowed for systematic planning of how clinical and research work may continue throughout the pandemic or be restarted as restrictions are abated. The urgency to provide and develop NIBS as an intervention for diverse neurological and mental health indications, and as a catalyst of fundamental brain research, is not dampened by the parallel efforts to address the most life-threatening aspects of COVID-19; rather in many cases the need for NIBS is heightened including the potential to mitigate mental health consequences related to COVID-19. ObjectiveTo facilitate the re-establishment of access to NIBS clinical services and research operations during the current COVID-19 pandemic and possible future outbreaks, we develop and discuss a framework for balancing the importance of NIBS operations with safety considerations, while addressing the needs of all stakeholders. We focus on Transcranial Magnetic Stimulation (TMS) and low intensity transcranial Electrical Stimulation (tES) - including transcranial Direct Current Stimulation (tDCS) and transcranial Alternating Current Stimulation (tACS). MethodsThe present consensus paper provides guidelines and good practices for managing and reopening NIBS clinics and laboratories through the immediate and ongoing stages of COVID-19. The document reflects the analysis of experts with domain-relevant expertise spanning NIBS technology, clinical services, and basic and clinical research – with an international perspective. We outline regulatory aspects, human resources, NIBS optimization, as well as accommodations for specific demographics. ResultsA model based on three phases (early COVID-19 impact, current practices, and future preparation) with an 11-step checklist (spanning removing or streamlining in-person protocols, incorporating telemedicine, and addressing COVID-19-associated adverse events) is proposed. Recommendations on implementing social distancing and sterilization of NIBS related equipment, specific considerations of COVID-19 positive populations including mental health comorbidities, as well as considerations regarding regulatory and human resource in the era of COVID-19 are outlined. We discuss COVID-19 considerations specifically for clinical (sub-)populations including pediatric, stroke, addiction, and the elderly. Numerous case-examples across the world are described. ConclusionThere is an evident, and in cases urgent, need to maintain NIBS operations through the COVID-19 pandemic, including anticipating future pandemic waves and addressing effects of COVID-19 on brain and mind. The proposed robust and structured strategy aims to address the current and anticipated future challenges while maintaining scientific rigor and managing risk.

Effects of cerebellar transcranial direct current stimulation on cerebellar-brain inhibition in humans: A systematic evaluation

BackgroundCerebellar transcranial direct current stimulation (ctDCS) is increasingly used to modulate cerebellar excitability and plasticity in healthy subjects and various patient populations. ctDCS parameters are poorly standardized, and its physiology remains little understood. Our aim was to compare the physiological effects of three different non-target electrode positions (buccinator muscle, supraorbital region, deltoid muscle). MethodsIn the first experiment, physiological after-effects of ctDCS were compared based on cerebellar-brain inhibition (CBI) in a group of 15 healthy right-handed participants. In the second experiment, CBI after-effects of ctDCS were assessed using different transcranial magnetic stimulation (TMS) intensities in 14 participants (CBI recruitment curve). The electric field distribution was calculated for each of the electrode montages based on a single anatomically accurate head model. ResultsAnodal and cathodal ctDCS polarities significantly decreased cerebellar-brain inhibition (CBI) with no substantial differences between the montages. Lower cerebellar TMS intensities resulted in decreased CBI following cathodal and increased CBI after anodal ctDCS. Computational modeling revealed minor differences in the electric field distribution between non-target electrode positions based on the effect size. ConclusionOur results show that the non-target electrode position has no significant impact on modeling results and physiological ctDCS after-effects. The recruitment of the cerebellar-M1 connection, however, varied depending on ctDCS polarity and cerebellar transcranial magnetic stimulation intensity, possibly due to diverse effects on different cell populations in the cerebellar cortex. This may be one of the reasons why ctDCS effects on functional measures are difficult to predict.

Effects of repetitive magnetic stimulation on the growth of primarily cultured hippocampus neurons in vitro and their expression of iron-containing enzymes.

Background: The mechanism of action of repetitive transcranial magnetic stimulation (rTMS) involves the generation of neuronal and action potentials utilizing induced currents in time-varying magnetic fields. However, the long-lasting and effective biological impact of magnetic stimulation does not appear to be completely explained by the transient magnetic field pulses. In this context, we hypothesized magnetic stimulation may affect the expression of iron-containing enzymes in neurons, mediating the long-lasting biological effects associated with this stimulus. Methods: Primarily cultured hippocampus neurons from SD rats were used as the cell model in this study. These were randomly divided into control, sham, and magnetic stimulation groups to probe into the effect of the magnetic field directly. The latter group received 40%, 60%, and 100% maximal stimulator output Tesla (1.68, 2.52, and 4.2 T) with low-frequency rTMS (1 Hz). The expression of iron-containing enzymes (catalase and aconitase) and non-ferrous enzymes (protein kinase A) was measured with Western blotting and ELISA. Results: The survival rates of neurons in the 40%T and 60%T groups were significantly increased in comparison to the controls (P<0.05), while those in the 100%T group showed cell damage, with slightly disturbed neurite connections and decreased survival rate. Furthermore, catalase and aconitase expression was higher in all of the stimulated groups in comparison to controls (P<0.05). On the other hand, the expression of the iron-containing enzymes decreased in the 100%T group in comparison with the 40%T and 60%T groups (P<0.05). Meanwhile, the expression of protein kinase A was not significantly increased in the groups which underwent magnetic stimulation. Conclusion: rTMS may increase the expression of ferrous enzymes but does not have a strong effect on non-ferrous enzymes. Excessive intensity of magnetic stimulation may reduce neuronal survival rate and affect the expression of iron-containing enzymes. The mechanism underlying the lasting effect of rTMS may be related to the increase of ferriferous expression induced by magnetic stimulation, with a clear correlation with stimulation intensity.

Full Activation Profiles and Integrity of Corticospinal Pathways in Adults With Bilateral Spastic Cerebral Palsy

Background. Dysfunction of corticospinal pathways has been implicated in motor impairments in people with bilateral spastic cerebral palsy (CP). While structural damage to corticospinal pathways in people with CP is known, its impact on the activation of these pathways is not. Objective. To provide the first, complete activation profile of corticospinal pathways in adults with CP using a full range of transcranial magnetic stimulation (TMS) intensities and voluntary contractions. Methods. TMS targeted the soleus muscle of 16 adults with bilateral spastic CP and 15 neurologically intact (NI) control participants. Activation profiles were generated using motor-evoked potentials (MEPs) produced by varying both stimulation intensity and degree of voluntary muscle activity. Anatomical integrity of corticospinal pathways was also measured with diffusion tractography. Results. Participants with CP had smaller MEPs produced by TMS at 1.2× active motor threshold during submaximal (20%) muscle activity and smaller maximal MEPs produced under any combination of stimulation intensity and voluntary muscle activity. At a fixed stimulation intensity, increasing voluntary muscle activity facilitated MEP amplitudes to a lesser degree in the participants with CP. Consistent differences in diffusion tractography suggested structural abnormalities in the corticospinal pathways of participants with CP that correlated with maximal MEPs. Conclusion. People with bilateral spastic CP have impaired activation of low and high-threshold corticospinal pathways to soleus motoneurons by TMS and reduced facilitation by voluntary activity that may be associated with structural damage to these pathways. These impairments likely contribute to impaired voluntary movement.

The effects of paired associative stimulation on sensorimotor function and the expression of MAP-2 and GAP-43 after focal cerebral ischemia and reperfasion

Objective To observe the effect of paired associative stimulation (PAS) on the recovery of sensorimotor function and to explore the mechanism in terms of neural plasticity. Methods Ninety male adult Sprague-Dawley rats were randomly divided into a sham operation group (Sham group), a model group (Model group) and a paired associative stimulation group (PAS group), each of 30. Each group was then subdivided into 7-, 14- and 28-day subgroups with 10 rats in each. A model of focal cerebral ischemia and reperfusion was established using the Longa suture method in the Model and PAS groups. The rats in the Sham group underwent the same surgical procedure except for the occlusion of the middle cerebral artery. The rats received 30 minutes of paired peripheral nerve stimulation and transcranial magnetic stimulation comprising 90 pairs at 0.05 Hz beginning 24 h after the occlusion. The impulse wave width of the peripheral nerve stimulation was 200 μs and the intensity was 6 mA. The intensity of the transcranial magnetic stimulation was 120% of the resting motor threshold. The other two groups weren′t given any intervention. Neurological function was tested using Garcia scores on the 1st, 7th, 14th and 28th day after surgery. The rats were then sacrificed and the expression of MAP-2 and GAP-43 in the ischemic penumbra were detected using western blotting and immunohistochemistry. Results No neurological dysfunction was observed in the Sham group at any time. Compared with the Sham group at the same time points, the average Garcia scores of the Model and PAS groups were significantly lower (P≤0.05). However, the average Garcia scores on the 7th, 14th and 28th day were significantly higher in the PAS group compared with the Model group at the same time points (P≤0.05). The average Garcia scores of the Model and PAS groups on the 28th day after surgery were significantly higher than those on the 1st day (P≤0.05), but only the PAS group′s average Garcia score on the 28th day was significantly higher than that on the 7th day. Compared with the Sham group at the same time points, the expression of MAP-2 and GAP-43 protein in the Model and PAS groups was significantly higher, but with that of the Model group significantly lower than that of the PAS group (all P≤0.05). The protein expression of MAP-2 and GAP-43 protein in the PAS group on the 14th day was significantly higher than on the 7th and 28th day (P≤0.05 for both). Conclusions PAS can promote the recovery of sensorimotor function after cerebral thrombosis, at least in rats. That may be due to its promoting the expression of the neuroplasticity-associated proteins MAP-2 and GAP-43 in the ischemic penumbra. Key words: Cerebral ischemia; Paired associative stimulation; Sensorimotor functioning; MAP-2; GAP-43; Peripheral nerve stimulation; Transcranial magnetic stimulation

Static magnetic field stimulation applied over the cervical spinal cord can decrease corticospinal excitability in finger muscle

ObjectiveTranscranial static magnetic field stimulation has recently been demonstrated to modulate cortical excitability. In the present study, we investigated the effect of transspinal static magnetic field stimulation (tsSMS) on excitability of the corticospinal tract. MethodsA compact magnet for tsSMS (0.45 Tesla) or a stainless steel cylinder for sham stimulation was positioned over the neck (C8 level) of 24 able-bodied subjects for 15 min. Using 120% of the resting motor threshold transcranial magnetic stimulation intensity, motor evoked potentials (MEPs) were measured from the first digital interosseous muscle before, during, and after the tsSMS or sham intervention. ResultsCompared with baseline MEP amplitudes were decreased during tsSMS, but not during sham stimulation. Additionally, during the intervention, MEP amplitudes were lower with tsSMS than sham stimulation, although these effects did not last after the intervention ceased. ConclusionsThe results suggest that static magnetic field stimulation of the spinal cord by a compact magnet can reduce the excitability of the corticospinal tract. SignificanceTransspinal static magnetic field stimulation may be a new non-invasive neuromodulatory tool for spinal cord stimulation. Its suppressive effect may be applied to patients who have pathological hyperexcitability of the spinal neural network.

Transcranial magnetic stimulation intensity affects exercise-induced changes in corticomotoneuronal excitability and inhibition and voluntary activation

Transcranial magnetic stimulation (TMS) of the motor cortex during voluntary contractions elicits electrophysiological and mechanical responses in the target muscle. The effect of different TMS intensities on exercise-induced changes in TMS-elicited variables is unknown, impairing data interpretation. This study aimed to investigate TMS intensity effects on maximal voluntary activation (VATMS), motor-evoked potentials (MEPs), and silent periods (SPs) in the quadriceps muscles before, during, and after exhaustive isometric exercise. Eleven subjects performed sets of ten 5-s submaximal isometric quadriceps contractions at 40% of maximal voluntary contraction (MVC) strength until task failure. Three different TMS intensities (I100, I75, I50) eliciting MEPs of 53±6%, 38±5% and 25±3% of maximal compound action potential (Mmax) at 20% MVC were used. MEPs and SPs were assessed at both absolute (40% baseline MVC) and relative (50%, 75%, and 100% MVC) force levels. VATMS was assessed with I100 and I75. When measured at absolute force level, MEP/Mmax increased during exercise at I50, decreased at I100 and remained unchanged at I75. No TMS intensity effect was observed at relative force levels. At both absolute and relative force levels, SPs increased at I100 and remained stable at I75 and I50. VATMS assessed at I75 tended to be lower than at I100. TMS intensity affects exercise-induced changes in MEP/Mmax (only when measured at absolute force level), SPs, and VATMS. These results indicate a single TMS intensity assessing maximal voluntary activation and exercise-induced changes in corticomotoneuronal excitability/inhibition may be inappropriate.