Effects of fatiguing unilateral plantar flexions on corticospinal and transcallosal inhibition in the primary motor hand area

Background

Corticospinal excitability of the primary motor cortex (M1) representing the hand muscle is depressed by bilateral lower limb muscle fatigue. The effects of fatiguing unilateral lower limb contraction on corticospinal excitability and transcallosal inhibition in the M1 hand areas remain unclear. The purpose of this study was to determine the effects of fatiguing unilateral plantar flexions on corticospinal excitability in the M1 hand areas and transcallosal inhibition originated from the M1 hand area contralateral to the fatigued ankle.

Methods

Ten healthy volunteers (26.2 ± 3.8 years) participated in the study. Using transcranial magnetic stimulation, we examined motor evoked potentials (MEPs) and interhemispheric inhibition (IHI) recorded from resting first dorsal interosseous (FDI) muscles before, immediately after, and 10 min after fatiguing unilateral lower limb muscle contraction, which was consisted of 40 unilateral maximal isometric plantar flexions intermittently with a 2-s contraction followed by 1 s of rest.

Results

We demonstrated no significant changes in MEPs in the FDI muscle ipsilateral to the fatigued ankle and decrease in IHI from the M1 hand area contralateral to the fatigued ankle to the ipsilateral M1 hand area after the fatiguing contraction. MEPs in the FDI muscle contralateral to the fatigued ankle were increased after the fatiguing contraction.

Conclusions

These results suggest that fatiguing unilateral lower limb muscle contraction differently influences corticospinal excitability of the contralateral M1 hand area and IHI from the contralateral M1 hand area to the ipsilateral M1 hand area. Although fatiguing unilateral lower limb muscle contraction increases corticospinal excitability of the ipsilateral M1 hand area, the increased corticospinal excitability is not associated with the decreased IHI.     

经颅磁刺激参数与结构要件的影响分析

为了进一步探索经颅磁刺激工作机理并改进或研制出新的经颅磁刺激激励源.本文从经颅磁刺激的原理推导出了磁场、感应电流及激励源原理电路电流的表达式,利用大脑-线圈和大脑-线圈-铁芯两种经颅磁刺激模型分析影响因素与头模型各组织的磁场和感应电流分布.对比分析表明电流的性质,线圈半径,线圈激励特性与铁芯对感应电流分布与电磁场分布有着本质的影响.对经颅磁刺激参数及结构要件的研究与分析可用于指导刺激线圈参数及激励源电路参数的设置,以及探索新的激励源制作.     

低频重复经颅磁刺激联合等速肌力训练模式干预对脑卒中的影响

摘要 目的：探讨等速肌力训练与低频重复经颅磁刺激对脑卒中患者下肢肌力的影响。方法：选择2020年2月到2021年8月在本院住院诊治的脑卒中患者96例作为研究对象,采用完全随机化1：1信封抽签原则把患者分为联合组与对照组各48例。对照组给予等速肌力训练,联合组在对照组治疗基础上给予低频重复经颅磁刺激治疗。两组在4周后记录下肢肌力变化情况。结果：（1）两组治疗后的美国国立卫生院神经功能缺损评分（NIHSS）低于治疗前,联合组低于对照组（P<0.05）。（2）两组治疗后的简化Fugl-Meye下肢评分高于治疗前,联合组高于对照组（P<0.05）。（3）两组治疗后的120 °/s时膝关节的伸肌与屈肌峰力矩体重比都高于治疗前,联合组高于对照组（P<0.05）。（4）两组治疗后的运动诱发电位潜伏期低于治疗前,波幅高于治疗前,联合组与对照组对比有差异（P<0.05）。结论：等速肌力训练联合低频重复经颅磁刺激在脑卒中患者的应用能促进改善神经功能与运动诱发电位,从而提高患者的下肢肌力与运动能力。     

Optimizing neuromuscular electrical stimulation for hand opening

Aim: To investigate the effect of introducing an interphase interval to a biphasic pulse on force production and muscle fatigue, during stimulation of the wrist and finger extensors and to determine whether the IPI effect on force is dependent on electrode position.

Methods: Electrically-induced contraction forces of the wrist and finger extensors were measured in 15 healthy subjects undergoing stimulation. These forces were assessed with interphase interval settings at 0, 100, and 200μs, with both electrodes located just distal to common extensor origin (proximal placement) or with the distal electrode placed over the extensor and abductor policies longus muscles (distal placement). The degree of discomfort related to stimulation sensation was evaluated using a numeric rating scale. Muscle fatigue was measured during proximal placement.

Results: Under both electrode locations, introduction of 100 or 200?μs interphase interval enhanced force production; yet, only the 100μs interphase interval increased force without increasing discomfort. Additionally, stimulation sensation was more comfortable with proximal placement. Introducing interphase interval significantly increased the muscle force output during a repetitive stimulation fatigue protocol.

Conclusions: When using neuromuscular electrical stimulation to activate the wrist and finger extensors, clinicians should consider locating both stimulating electrodes proximally over the extensor surface of the forearm and apply a 100?µs interphase interval to a biphasic pulse. Future research that should establish these findings in individuals with various pathologies, especially in patients with residual hand spasticity.     

经颅磁刺激联合语言训练对儿童语言发育迟缓的应用价值

目的:探讨经颅磁刺激联合语言训练对儿童语言发育迟缓的应用价值。方法:选取2015年3月-2016年3月我院收治的100例语言发育迟缓儿童作为本次研究的对象,采用随机数字表法将患者分为对照组与观察组各50例,对照组采用常规语言训练治疗,观察组则采用经颅磁刺激联合语言训练治疗,两组疗程皆为3个月。根据汉语儿童语言发育迟缓评定法和儿童神经心理发育测试分别评价治疗效果以及治疗前后发育商的变化情况。结果:观察组治疗有效率为98.0%,显著高于对照组的87.0%(P0.05);治疗后1、2、3月两组语言发育商、发育商较治疗前均有了显著改善,且观察组显著优于对照组(P0.05);观察组发育商正常率为80.0%,显著高于对照组的66.0%(P0.05)。结论:经颅磁刺激联合语言训练疗效理想,能够有效改善语言发育迟缓儿童的发育商,值得在临床上推广。     

经颅磁刺激在大脑皮质研究中的应用和进展

经颅磁刺激（TMS）是一种能够在脑中感应聚焦电流,瞬间调制大脑皮质的无创方法,在临床研究、基础神经学和诊治疾病等方面有许多应用。通过记录运动皮质诱发电位（MEPs),TMS已经或将成为探测脑下运动路径传导、评价皮质兴奋性、皮质映射和研究皮质塑性的常规工具。TMS能够主动干预脑功能,这种特性使它成为研究正常人脑－行为关系的独特技术,可以建立脑活动与任务完成之间的因果关系,探索脑功能连接。近年来的许多实验又表明,TMS在运动紊乱和精神疾病方面有潜在的治疗作用,但达到临床应用还有一定距离。     

The Anatomical and Evolutionary Relationship between Self-awareness and Theory of Mind

Although theories that examine direct links between behavior and brain remain incomplete, it is known that brain expansion significantly correlates with caloric and oxygen demands. Therefore, one of the principles governing evolutionary cognitive neuroscience is that cognitive abilities that require significant brain function (and/or structural support) must be accompanied by significant fitness benefit to offset the increased metabolic demands. One such capacity is self-awareness (SA), which (1) is found only in the greater apes and (2) remains unclear in terms of both cortical underpinning and possible fitness benefit. In the current experiment, transcranial magnetic stimulation (TMS) was applied to the prefrontal cortex during a spatial perspective-taking task involving self and other viewpoints. It was found that delivery of TMS to the right prefrontal region disrupted self-, but not other-, perspective. These data suggest that self-awareness may have evolved in concert with other right hemisphere cognitive abilities.

经颅磁刺激联合高压氧（HBO)治疗脑梗死240 例临床疗效分析

目的:观察经颅磁刺激(transcranial magnetic stimulation,TMS)联合高压氧(hyperbaricoxygen,HBO)治疗脑梗死的临床疗效。方法:采用随机数字表法将240例脑梗死患者分为联合治疗组、HBO组及常规组,每组80例。常规组患者给予常规治疗,HBO组患者在常规干预基础上辅以HBO治疗,联合治疗组患者则在常规干预基础上辅以HBO及TMS联合治疗。上述治疗均以10 d为1个疗程,共治疗2个疗程。于治疗前、治疗2个疗程后比较各组患者神经功能缺损程度,并同时于上述时间点检测各组患者中枢运动传导时间(CMCT)及血清中脑源性神经营养因子(BDNF)、神经生长因子(NGF)表达情况。结果:各组患者分别经2个疗程治疗后,发现联合治疗组NIHSS评分、总有效率均显著优于HBO组及常规组水平(均P0.05);另外联合治疗组血清中BDNF含量与NGF含量均较治疗前明显升高(P0.05),与常规组及HBO组间差异亦具有统计学意义(均P0.05)。结论:TMS联合HBO治疗脑梗死具有协同作用,能进一步改善患者受损神经功能及日常生活质量,其治疗机制可能与增强神经营养因子表达有关。     

Time-dependent effects of neuromuscular electrical stimulation on changes in spinal excitability are dependent on stimulation frequency: A preliminary study in healthy adults

Neuromuscular electrical stimulation (NMES) can be used as treatment for spasticity. The present study examined differences in time-dependent effects of NMES depending on stimulation frequency. Forty healthy subjects were separated into four groups (no-stim, NMES of 50, 100, and 200?Hz). The un-conditioned H-reflex amplitude and the H-reflex conditioning-test paradigm were used to measure the effectiveness on monosynaptic Ia excitation of motoneurons in the soleus (SOL) muscle, disynaptic reciprocal Ia inhibition from tibialis anterior (TA) to SOL, and presynaptic inhibition of SOL Ia afferents. Each trial consisted of a 30-min period of NMES applied to the deep peroneal nerve followed by a 30-min period with no stimulation to measure prolonged effects. Measurements were performed periodically. Stimulation applied at all frequencies produced a significant reduction in monosynaptic Ia excitation of motoneurons in the SOL muscle, however, only stimulation with 50?Hz showed prolonged reduction after NMES. NMES frequency did not affect the amount of disynaptic reciprocal Ia inhibition and presynaptic inhibition of Ia afferents. The results show a frequency-dependent effect of NMES on the monosynaptic Ia excitation of motoneurons. This result has implications for selecting the optimal NMES frequency for treatment in patients with spasticity.     

Does interhemispheric communication relate to the bilateral function of muscles? A study of scapulothoracic muscles using transcranial magnetic stimulation

Interhemispheric connections have been demonstrated between the motor cortex controlling muscle pairs. However, these investigations have tended to concentrate upon hand muscles. We have extended these investigations to proximal muscles that control the scapula upon the trunk and help to move and stabilise the shoulder. Using a paired pulse transcranial magnetic stimulation protocol, the interhemispheric interactions between different shoulder girdle muscle pairs, serratus anterior, upper trapezius and lower trapezius were investigated. Test motor evoked potentials were conditioned using conditioning pulse intensities of 80% and 120% of active motor threshold at three different condition-test intervals, during three different tasks. Interhemispheric inhibition was observed in upper trapezius using a conditioning intensity of 120% and condition-test interval of 8 ms (17 ± 18%, p < 0.007). A trend towards inhibition was observed in lower trapezius and serratus anterior using a conditioning intensity of 120% and a condition-test interval of 8 ms (13 ± 22%; p < 0.07 and 10 ± 19% respectively; p < 0.07). No interhemispheric facilitation was evoked. The study demonstrates that a low level of interhemispheric inhibition rather than interhemispheric facilitation could be evoked between these muscle pairs.     

Noninvasive brain stimulation with transcranial magnetic or direct current stimulation (TMS/tDCS)—From insights into human memory to therapy of its dysfunction

Noninvasive stimulation of the brain by means of transcranial magnetic stimulation (TMS) or transcranial direct current stimulation (tDCS) has driven important discoveries in the field of human memory functions. Stand-alone or in combination with other brain mapping techniques noninvasive brain stimulation can assess issues such as location and timing of brain activity, connectivity and plasticity of neural circuits and functional relevance of a circumscribed brain area to a given cognitive task. In this emerging field, major advances in technology have been made in a relatively short period. New stimulation protocols and, especially, the progress in the application of tDCS have made it possible to obtain longer and much clearer inhibitory or facilitatory effects even after the stimulation has ceased. In this introductory review, we outline the basic principles, discuss technical limitations and describe how noninvasive brain stimulation can be used to study human memory functions in vivo. Though improvement of cognitive functions through noninvasive brain stimulation is promising, it still remains an exciting challenge to extend the use of TMS and tDCS from research tools in neuroscience to the treatment of neurological and psychiatric patients.