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1.
J Neural Eng ; 18(4)2021 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-34475274

RESUMO

Objective.Transcranial magnetic stimulation (TMS) can be used to safely and noninvasively activate brain tissue. However, the characteristic parameters of the neuronal activation have been largely unclear. In this work, we propose a novel neuronal activation model and develop a method to infer its parameters from measured motor evoked potential signals.Approach.The connection between neuronal activation due to an induced electric field and a measured motor threshold is modeled. The posterior distribution of the model parameters are inferred from measurement data using Bayes' formula. The measurements are the active motor thresholds obtained with multiple stimulating coil locations, and the parameters of the model are the location, preferred direction of activation, and threshold electric field value of the activation site. The posterior distribution is sampled using a Markov chain Monte Carlo method. We quantify the plausibility of the model by calculating the marginal likelihood of the measured thresholds. The method is validated with synthetic data and applied to motor threshold measurements from the first dorsal interosseus muscle in five healthy participants.Main results.The method produces a probability distribution for the activation location, from which a minimal volume where the activation occurs with 95% probability can be derived. For eight or nine stimulating coil locations, the smallest such a volume obtained was approximately 100 mm3. The 95% probability volume intersected the pre-central gyral crown and the anterior wall of the central sulcus, and the preferred direction was perpendicular to the central sulcus, both findings being consistent with the literature. Furthermore, it was not possible to rule out if the activation occurred either in the white or grey matter. In one participant, two distinct activations sites were found while others exhibited a unique site.Significance.The method is both generic and robust, and it lays a foundation for a framework that enables accurate analysis and characterization of TMS activation mechanisms.


Assuntos
Córtex Motor , Estimulação Magnética Transcraniana , Teorema de Bayes , Mapeamento Encefálico , Potencial Evocado Motor , Humanos
2.
Neurosurg Focus ; 51(3): E7, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34469868

RESUMO

OBJECTIVE: Motor cortical dysfunction has been shown to be reversible in patients with unilateral atherosclerotic disease after cerebral revascularization. Moyamoya vasculopathy (MMV) is a rare bilateral stenoocclusive cerebrovascular disease. The aim of this study was to analyze the corticospinal excitability and the role of bypass surgery in restoring cortical motor function in patients by using navigated transcranial magnetic stimulation (nTMS). METHODS: Patients with bilateral MMV who met the criteria for cerebral revascularization were prospectively included. Corticospinal excitability, cortical representation area, and intracortical inhibition and facilitation were assessed by nTMS for a small hand muscle (first dorsal interosseous) before and after revascularization. The clinically and/or hemodynamically more severely affected hemisphere was operated first as the leading hemisphere. Intra- and interhemispheric differences were analyzed before and after direct or combined revascularization. RESULTS: A total of 30 patients with bilateral MMV were examined by nTMS prior to and after revascularization surgery. The corticospinal excitability was higher in the leading hemisphere compared with the non-leading hemisphere prior to revascularization. This hyperexcitability was normalized after revascularization as demonstrated in the resting motor threshold ratio of the hemispheres (preoperative median 0.97 [IQR 0.89-1.08], postoperative median 1.02 [IQR 0.94-1.22]; relative effect = 0.61, p = 0.03). In paired-pulse paradigms, a tendency for a weaker inhibition of the leading hemisphere was observed compared with the non-leading hemisphere. Importantly, the paired paradigm also demonstrated approximation of excitability patterns between the two hemispheres after surgery. CONCLUSIONS: The study results suggested that, in the case of a bilateral chronic ischemia, a compensation mechanism between both hemispheres seemed to exist that normalized after revascularization surgery. A potential role of nTMS in predicting the efficacy of revascularization must be further assessed.


Assuntos
Revascularização Cerebral , Transtornos Cerebrovasculares , Doença de Moyamoya , Potencial Evocado Motor , Mãos , Humanos , Doença de Moyamoya/diagnóstico por imagem , Doença de Moyamoya/cirurgia , Estimulação Magnética Transcraniana
3.
Spine (Phila Pa 1976) ; 46(20): E1069-E1076, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34559750

RESUMO

STUDY DESIGN: Prospective multicenter cohort study. OBJECTIVE: The aim of this study was to validate an alarm point of intraoperative neurophysiological monitoring () formulated by the Monitoring Working Group (WG) of the Japanese Society for Spine Surgery and Related Research (JSSR). SUMMARY OF BACKGROUND DATA: The Monitoring WG of the JSSR formulated an alarm point of IONM using transcranial electrical stimulation-muscle motor evoked potentials (Tc(E)-MEPs) and has conducted a prospective multicenter study. The validity of the JSSR alarm point of ≥ 70% decreased in Tc(E)-MEPs for each high-risk surgery and any other spine surgeries has not been verified. METHODS: Patients who underwent spine and spinal cord surgery with IONM in 16 Japanese spine centers in the Monitoring WG of the JSSR from 2017 to 2018 were enrolled. The patients were divided into the high-risk surgery group (Group HR) and the common surgery group (Group C). Group HR was defined by ossification of the posterior longitudinal ligament (OPLL), spinal deformity, and spinal cord tumor. Group C was classified as other spine surgeries. The alarm point was defined as a ≥70% decrease in the Tc(E)-MEPs. RESULTS: In Group HR, the sensitivity and specificity were 94.4% and 87.0%, respectively. In Group C, the sensitivity and specificity were 63.6% and 91.9%. The sensitivity in Group C was statistically lower than that in Group HR (P < 0.05). In Group HR, the sensitivity and specificity in OPLL were 100% and 86.9%, respectively. The sensitivity and specificity in spinal deformity were 87.5% and 84.8%, respectively, and the sensitivity and specificity in spinal cord tumors were 92.9% and 89.9%, respectively. The sensitivity and specificity in each high-risk surgery showed no significant difference. CONCLUSION: The alarm point of IONM by the Monitoring WG of the JSSR appeared to be valid for each disease in Group HR. Meanwhile, applying the JSSR alarm point for Group C potentially needed attention.Level of Evidence: 3.


Assuntos
Monitorização Neurofisiológica Intraoperatória , Estudos de Coortes , Potencial Evocado Motor , Humanos , Japão , Estudos Prospectivos , Medula Espinal
4.
Neuroscience ; 472: 11-24, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34333064

RESUMO

Dual-site transcranial magnetic stimulation (TMS) is a promising tool to measure supplementary motor area and primary motor cortex (SMA-M1) connectivity in younger and older adults, and could be used to understand the pathophysiology of movement disorders. However, test re-test reliability of dual-site TMS measures of SMA-M1 connectivity has not been established. We examined the reliability of SMA-M1 connectivity using dual-site TMS in two sessions in 30 younger and 30 older adults. For dual-site TMS, a conditioning pulse delivered to SMA (140% of active motor threshold) preceded a test pulse delivered to M1 (intensity that elicited MEPs of ~1 mV) by inter-stimulus intervals (ISI) of 6 ms, 7 ms, and 8 ms. Moderate intraclass correlation coefficients (ICC) were found for SMA-M1 connectivity at an ISI of 7 ms in younger (ICC: 0.69) and older adults (ICC: 0.68). Poor ICCs were found for SMA-M1 connectivity at ISIs of 6 ms and 8 ms in both age groups (ICC range: 0.01-0.40). We report evidence for stable measures of SMA-M1 connectivity at an ISI of 7 ms in both age groups. These findings are foundational for future research developing evidence-based interventions to strengthen SMA-M1 connectivity to improve bilateral motor control in older adults and populations with movement disorders.


Assuntos
Córtex Motor , Estimulação Magnética Transcraniana , Potencial Evocado Motor , Movimento , Reprodutibilidade dos Testes
5.
Spine (Phila Pa 1976) ; 46(18): 1226-1233, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34435985

RESUMO

STUDY DESIGN: Retrospective study. OBJECTIVE: To explore a relation between somatosensory- and motor-evoked potential (SEPs, MEPs) and corresponding thoracic cord function for thoracic spinal decompression surgery (TSDS) in patients with neurological deficit. SUMMARY OF BACKGROUND DATA: Although SEPs and MEPs monitoring has been developed as an essential technique in spinal surgery. There are limited data on the reliability of using SEPs and MEPs for TSDS and its prognosis. METHODS: One hundred twenty patients underwent TSDS in our hospital, 91 patients completed the trial. All the patients were divided into three subgroups according to the changes of MEPs and SEPs: neither SEPs nor MEP deteriorated -. Simply MEP deteriorated and both SEPs and MEP deteriorated -. Bispectral (BIS) was used to monitor the depth of sedation, which ranged from 40 to 60 by varying the infusion speed of anesthetics. The pre- and postoperative spinal function was assessed by muscle strength and Japanese Orthopaedic Association (JOA) score at three time points:1) before surgery; 2) immediately after general anesthesia recovery; 3) after 3-month follow-up. RESULTS: Sixty-nine cases showed neither SEPs nor MEP deteriorated -, 10 cases showed only MEP deteriorated, and 12 cases showed both SEPs and MEP deteriorated -. The patients in the group where neither SEPs nor MEP deteriorated had the best recovery of the extremity muscle strength, the shortest recovery time (8.10 ±â€Š1.60, P < 0.05), and toe movement time (8.50 ±â€Š1.60, P < 0.05). There is a strong correlation between SEPs variability ratio at T4 time point and JOA recovery ratio (JOA RR) in the 3-month follow-up. CONCLUSION: Combined SEPs and MEPs monitoring are important for TSDS in patients with neurological deficit and it is helpful for evaluating postoperative prognosis. It is more accurate to record SEPs at T4 time point to predict the patients' prognosis.Level of Evidence: 3.


Assuntos
Descompressão , Potencial Evocado Motor , Humanos , Prognóstico , Reprodutibilidade dos Testes , Estudos Retrospectivos
6.
BMJ Case Rep ; 14(8)2021 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-34417230

RESUMO

A 12-year-old girl underwent surgery for Lenke type 4 adolescent idiopathic scoliosis. After scoliosis correction, the transcranial motor-evoked potential (Tc-MEP) showed no alarm. However, the Tc-MEP amplitude had declined ~10 min after correction, with a normal blood pressure (BP) and body temperature and without any technical monitoring errors. Therefore, we suspected indirect spinal cord ischaemia because of the delayed true-positive Tc-MEP alarm. All the strong corrections made loss of Tc-MEP and all the correction releases made recovers of waveform. Finally, a weak correction was performed, and the Tc-MEP amplitude was recovered. Because transient spinal cord ischaemia due to correction of triple curves may cause a delayed monitoring alarm, the monitoring team should frequently check Tc-MEP after these manoeuvres. This patient had no neurological deficits and was considered to be a rescue case.


Assuntos
Cifose , Procedimentos Ortopédicos , Escoliose , Adolescente , Criança , Potencial Evocado Motor , Feminino , Humanos , Procedimentos Neurocirúrgicos , Escoliose/cirurgia
8.
Brain Inj ; 35(10): 1143-1161, 2021 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-34384288

RESUMO

OBJECTIVES: To investigate neurophysiological alterations within the typical symptomatic period after concussion (1-month) and throughout recovery (6-months) in adolescents; and (2) to examine relationships between neurophysiological and upper limb kinematic outcomes.METHODS: 18 adolescents with concussion were compared to 17 healthy controls. Transcranial magnetic stimulation (TMS) was used to assess neurophysiological differences between groups including: short- and long-interval intracortical inhibition, intracortical facilitation, short- and long-latency afferent inhibition, afferent facilitation, and transcallosal inhibition (TCI). Behavioral measures of upper limb kinematics were assessed with a robotic device.RESULTS: Mixed model analysis of neurophysiological data identified two key findings. First, participants with concussion demonstrated delayed onset of interhemispheric inhibition, as indexed by TCI, compared to healthy controls. Second, our exploratory analysis indicated that the magnitude of TCI onset delay in adolescents with concussion was related to upper limb kinematics.CONCLUSIONS: Our findings indicate that concussion in adolescence alters interhemispheric communication. We note relationships between neurophysiological and kinematic data, suggesting an affinity for individuals with less concussion-related physiological change to improve their motor behavior over time. These data serve as an important step in future development of assessments (neurobiological and clinical) and interventions for concussion.


Assuntos
Córtex Motor , Adolescente , Criança , Comunicação , Potencial Evocado Motor , Lateralidade Funcional , Humanos , Inibição Neural , Estimulação Magnética Transcraniana
9.
Neuropsychologia ; 161: 107992, 2021 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-34391807

RESUMO

OBJECTIVE: The Rubber Hand Illusion (RHI) manipulates body ownership experimentally and helps investigate the related neurophysiological processes. This study aimed to evaluate motor cortex excitability that hypothesized changed due to illusion. METHOD: Twenty-one healthy (twelve male, nine female), right-handed volunteers aged between 25 and 50 years were recruited to the study. Short-Latency Afferent Inhibition (SAI) was evaluated by transcranial magnetic stimulation (TMS) given with a figure-of-eight-shaped coil from the left motor cortex, 21 ms after peripheral electrical stimulation. Short-Interval Intracortical Inhibition (SICI) and Intracortical Facilitation (ICF) were investigated using a paired-pulse TMS at interstimulus intervals (ISI) of 1, 2.5, 3 ms and 15, 20, 25 ms, respectively. We used custom-made illusion setups for TMS paradigms. SAI, SICI and ICF was evaluated before, during and 15 min after the RHI. RESULTS: Results of the study revealed significantly high SAI during illusion compared to pre-illusion, but no difference was found between post-illusion 15th minutes and control measurements. Significantly reduced SICI at 2.5 and 3 ms ISI obtained during illusion, while RHI did not affect SICI at 1 ms ISI and ICF. SIGNIFICANCE: Body ownership illusion modulates the motor cortex excitability, possibly through altered sensory processing and sensorimotor integration.


Assuntos
Excitabilidade Cortical , Ilusões , Adulto , Potencial Evocado Motor , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Inibição Neural , Propriedade , Estimulação Magnética Transcraniana
10.
Eur J Neurosci ; 54(4): 5444-5461, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34251703

RESUMO

Homeostatic plasticity complements synaptic plasticity by stabilising neural activity within a physiological range. In humans, homeostatic plasticity is investigated using two blocks of non-invasive brain stimulation (NIBS) with an interval without stimulation between blocks. The aim of this systematic review and meta-analysis was to investigate the effect of homeostatic plasticity induction protocols on motor evoked potentials (MEP) in healthy participants. Four databases were searched (Medline, Scopus, Embase and Cochrane library). Studies describing the application of two blocks of NIBS of the primary motor cortex with an interval of no stimulation between blocks reporting changes in corticospinal excitability by MEP amplitude were included. Thirty-seven reports with 55 experiments (700 participants) were included. Study quality was considered poor overall, with heterogeneity in study size, sample and designs. Two blocks of excitatory stimulation at the primary motor cortex produced a homeostatic response (decreased MEP) between 0 and 30 min post-protocols, when compared with a single stimulation block. Two blocks of inhibitory stimulation at the primary motor cortex using interval duration of 10 min or less produced a homeostatic response (increased MEP) between 0 and 30 min post-protocols, when compared with a single stimulation block. There were no differences in MEPs when compared with baseline MEPs. In conclusion, homeostatic plasticity induction using two blocks of NIBS with an interval of 10 min or less without stimulation between blocks produces a homeostatic response up to 30 min post-protocol. Improvements in participant selection, sample sizes and protocols of NIBS techniques are needed.


Assuntos
Córtex Motor , Estimulação Magnética Transcraniana , Potencial Evocado Motor , Voluntários Saudáveis , Humanos , Metanálise como Assunto , Plasticidade Neuronal , Revisões Sistemáticas como Assunto
11.
Int J Mol Sci ; 22(13)2021 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-34281270

RESUMO

Functional recovery after peripheral nerve injury (PNI) is poor, mainly due to the slow and incomplete regeneration of injured axons. Experimental therapies that increase the excitability of the injured axons have proven remarkably successful in promoting regeneration, but their clinical applicability has been limited. Bioluminescent optogenetics (BL-OG) uses luminopsins, fusion proteins of light-generating luciferase and light-sensing ion channels that could be used to increase neuronal excitability if exposed to a suitable substrate. Excitatory luminopsins were expressed in motoneurons of transgenic mice and in wildtype mice transduced with adeno-associated viral vectors. Intraperitoneal administration of coelenterazine (CTZ), a known luciferase substrate, generated intense bioluminescence in peripheral axons. This bioluminescence increased motoneuron excitability. A single administration of CTZ immediately after sciatic nerve transection and repair markedly enhanced motor axon regeneration. Compound muscle action potentials were 3-4 times larger than controls by 4 weeks after injury. The results observed with transgenic mice were comparable to those of mice in which the luminopsin was expressed using viral vectors. Significantly more motoneurons had successfully reinnervated muscle targets four weeks after nerve injury in BL-OG treated mice than in controls. Bioluminescent optogenetics is a promising therapeutic approach to enhancing axon regeneration after PNI.


Assuntos
Regeneração Nervosa/fisiologia , Optogenética/métodos , Traumatismos dos Nervos Periféricos/terapia , Animais , Axônios/fisiologia , Modelos Animais de Doenças , Potencial Evocado Motor , Feminino , Humanos , Imidazóis/administração & dosagem , Substâncias Luminescentes/administração & dosagem , Proteínas Luminescentes/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios Motores/fisiologia , Traumatismos dos Nervos Periféricos/fisiopatologia , Pirazinas/administração & dosagem , Proteínas Recombinantes de Fusão/genética , Medicina Regenerativa/métodos
13.
Neuroimage Clin ; 31: 102738, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34198038

RESUMO

Action preparation relies on the operation of control processes that modulate the excitability of the corticospinal tract. On the one hand, excitatory processes prepare the motor system for the forthcoming response; the stronger these influences, the stronger the tendency to act. On the other hand, inhibitory influences allow to suppress inappropriate actions and, more generally, to ensure some sort of impulse control. Because an impairment in these processes could foster inappropriate drinking behavior, the present study aimed at evaluating the motor correlates of such excitatory and inhibitory influences in non-treatment seeking heavy drinkers (HDs) and inpatients suffering from severe alcohol use disorder (SAUDs). Besides, as cue-elicited craving might further alter these processes, we also assessed the impact of an alcohol-related exposure. To do so, 15 healthy controls (HCs), 15 HDs and 15 SAUDs performed a choice reaction time task after having been immersed in a neutral or an alcohol-related environment, using virtual reality videos. Importantly, single-pulse transcranial magnetic stimulation was applied over the left and the right primary motor cortex during the task to elicit motor-evoked potentials in a set of hand muscles allowing us to specifically probe the impact of excitatory and inhibitory processes on motor activity. Our data indicate that excitatory influences are particularly high in both HDs and SAUDs, especially in the dominant hand, an effect that was not observed in HCs. By contrast, inhibitory influences were found to be perfectly normal in HDs, while they were lacking in SAUDs. Furthermore, the alcohol-related exposure enhanced the level of self-reported craving, but this effect only arose in HDs and did not significantly alter the strength of excitatory and inhibitory influences. Overall, although these results have to be taken with caution due to the small sample sizes, this study suggests that enhanced excitatory processes characterize both HDs and SAUDs, while weaker inhibitory influences only concern SAUDs. Hence, an abnormally strong tendency to act could represent a common feature of hazardous drinking, leading individuals to excessive alcohol consumption, whereas deficient impulse control would be a hallmark of more severe forms of AUD, potentially due to the chronic neurotoxic effects of alcohol. Finally, although an alcohol-related exposure does not seem to affect excitatory and inhibitory processes at play during action preparation per se, future works should evaluate changes in corticospinal excitability during the preparation of responses specifically targeting alcohol-related cues.


Assuntos
Alcoolismo , Córtex Motor , Potencial Evocado Motor , Humanos , Tratos Piramidais , Estimulação Magnética Transcraniana
14.
J Clin Neurosci ; 90: 363-369, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34275577

RESUMO

OBJECTIVE: To investigate the effects of paired associated stimulation (PAS) with different stimulation position on motor cortex excitability and upper limb motor function in patients with cerebral infarction. METHOD: A total of 120 volunteers with cerebral infarction were randomly divided into four groups. Based on conventional rehabilitation treatment, the PAS stimulation group was given the corresponding position of PAS treatment once a day for 28 consecutive days. The MEP amplitude and RMT of both hemispheres were assessed before and after treatment, and a simple upper limb Function Examination Scale (STEF) score, simplified upper limb Fugl-Meyer score (FMA), and improved Barthel Index (MBI) were used to assess upper limb motor function in the four groups. RESULTS: Following PAS, the MEP amplitude decreased, and the RMT of abductor pollicis brevis (APB) increased on the contralesional side, while the MEP amplitude increased and the RMT of APB decreased on the ipsilesional side. After 28 consecutive days the scores of STEF, FMA, and MBI in the bilateral stimulation group were significantly better than those in the ipsilesional stimulation group and the contralesional stimulation group, but there was no significant difference in the scores of STEF, FMA, and MBI between the ipsilesional stimulation group and the contralesional stimulation group. CONCLUSION: The excitability of the motor cortex can be changed when the contralesional side or the ipsilesional side was given the corresponding PAS stimulation, while the bilateral PAS stimulation can more easily cause a change of excitability of the motor cortex, resulting in better recovery of the upper limb function.


Assuntos
Infarto Cerebral/fisiopatologia , Infarto Cerebral/reabilitação , Terapia por Estimulação Elétrica , Córtex Motor/fisiopatologia , Extremidade Superior/fisiopatologia , Adulto , Potencial Evocado Motor , Feminino , Lateralidade Funcional , Humanos , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/inervação , Músculo Esquelético/fisiologia , Reabilitação do Acidente Vascular Cerebral/métodos , Estimulação Magnética Transcraniana
15.
Nat Commun ; 12(1): 4399, 2021 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-34285221

RESUMO

The decline of neuronal synapses is an established feature of ageing accompanied by the diminishment of neuronal function, and in the motor system at least, a reduction of behavioural capacity. Here, we have investigated Drosophila motor neuron synaptic terminals during ageing. We observed cumulative fragmentation of presynaptic structures accompanied by diminishment of both evoked and miniature neurotransmission occurring in tandem with reduced motor ability. Through discrete manipulation of each neurotransmission modality, we find that miniature but not evoked neurotransmission is required to maintain presynaptic architecture and that increasing miniature events can both preserve synaptic structures and prolong motor ability during ageing. Our results establish that miniature neurotransmission, formerly viewed as an epiphenomenon, is necessary for the long-term stability of synaptic connections.


Assuntos
Envelhecimento/fisiologia , Neurônios Motores/fisiologia , Terminações Pré-Sinápticas/fisiologia , Transmissão Sináptica/fisiologia , Animais , Animais Geneticamente Modificados , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Potencial Evocado Motor/fisiologia , Masculino , Microscopia Eletrônica , Modelos Animais , Neurônios Motores/ultraestrutura , Músculos/inervação , Músculos/fisiologia , Músculos/ultraestrutura , Terminações Pré-Sinápticas/ultraestrutura , Fatores de Tempo
16.
Pain ; 162(8): 2287-2296, 2021 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-34256382

RESUMO

ABSTRACT: Pain is a ubiquitous experience encompassing perceptual, autonomic, and motor responses. Expectancy is known to amplify the perceived and autonomic components of pain, but its effects on motor responses are poorly understood. Understanding expectancy modulation of corticospinal excitability has important implications regarding deployment of adaptive and maladaptive protective behaviours in anticipation of pain. We developed a protocol to compare corticospinal excitability to expected high pain, expected low pain, and critically low pain when high pain was expected. Expecting high pain suppressed corticospinal excitability and heightened perceptual and autonomic responses to the low-pain stimulus, as with increased noxious stimulation (ie, expected high pain). Multilevel modelling revealed that perceived pain mediated the effect of both noxious stimulation and this expectancy-modulated pain on autonomic responses, but corticospinal excitability did not. These results demonstrate that merely expecting pain influenced all pain components. Findings shed new light on the aetiology of expectancy-modulated pain, whereby expecting pain mobilises the motor system to protect the body from harm by a protective withdrawal reflex, associated with reduced corticospinal excitability, and activates similar processes as increased nociceptive stimulation. This has significant practical implications for the treatment of pain, particularly in scenarios where avoidance of pain-related movement contributes to its maintenance.


Assuntos
Potencial Evocado Motor , Tratos Piramidais , Eletromiografia , Humanos , Músculo Esquelético , Dor , Percepção da Dor , Estimulação Magnética Transcraniana
17.
Neurosci Biobehav Rev ; 128: 678-692, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34274404

RESUMO

Action preparation is characterized by a set of complex and distributed processes that occur in multiple brain areas. Interestingly, dual-coil transcranial magnetic stimulation (TMS) is a relevant technique to probe effective connectivity between cortical areas, with a high temporal resolution. In the current systematic review, we aimed at providing a detailed picture of the cortico-cortical interactions underlying action preparation focusing on dual-coil TMS studies. We considered four theoretical processes (impulse control, action selection, movement initiation and action reprogramming) and one task modulator (movement complexity). The main findings highlight 1) the interplay between primary motor cortex (M1) and premotor, prefrontal and parietal cortices during action preparation, 2) the varying (facilitatory or inhibitory) cortico-cortical influence depending on the theoretical processes and the TMS timing, and 3) the key role of the supplementary motor area-M1 interactions that shape the preparation of simple and complex movements. These findings are of particular interest for clinical perspectives, with a need to better characterize functional connectivity deficiency in clinical population with altered action preparation.


Assuntos
Córtex Motor , Estimulação Magnética Transcraniana , Encéfalo , Mapeamento Encefálico , Potencial Evocado Motor , Humanos , Lobo Parietal
18.
Artigo em Inglês | MEDLINE | ID: mdl-34242169

RESUMO

Paired associative nerve stimulation (PANS) was proposed as a potential nerve rehabilitation treatment strategy. However, few relevant documents are available regarding the strategy, and only a few clinical studies have involved healthy people. To determine the feasibility of the neurorehabilitation treatment and to estimate the effect of PANS on nerve plasticity for individuals with incomplete spinal cord injury (iSCI), a design combining repetitive transcranial magnetic stimulation (rTMS) with trans-spinal electrical stimulation was developed for treating individuals with iSCI in this pilot case study. First, a novel PANS system with multiple stimulation modes was designed and verified with resistors and a metal coil as load. Then, the system was applied to three individuals with iSCI, and five types of paired associative stimulation was performed to confirm the feasibility of the system and determine the most effective treatment strategy. The preliminary result showed that 20-Hz rTMS combined with cathodal trans-spinal direct current stimulation (tsDCS) had the greatest effect on corticospinal excitability. Next, stimulations of 20-Hz rTMS (brain) and sham (spine) as well as sham (brain) and cathode tsDCS (spine) were administered to individuals with iSCI, and the results revealed that paired associative stimulation of brain and spine was more effective than only 20-Hz rTMS brain stimulation or cathodal tsDCS stimulation for corticospinal plasticity.


Assuntos
Reabilitação Neurológica , Traumatismos da Medula Espinal , Potencial Evocado Motor , Humanos , Plasticidade Neuronal , Medula Espinal , Traumatismos da Medula Espinal/terapia , Estimulação Magnética Transcraniana
19.
Exp Brain Res ; 239(9): 2661-2678, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34269850

RESUMO

It is commonly accepted that the brains capacity to change, known as plasticity, declines into old age. Recent studies have used a variety of non-invasive brain stimulation (NIBS) techniques to examine this age-related decline in plasticity in the primary motor cortex (M1), but the effects seem inconsistent and difficult to unravel. The purpose of this review is to provide an update on studies that have used different NIBS techniques to assess M1 plasticity with advancing age and offer some new perspective on NIBS strategies to boost plasticity in the ageing brain. We find that early studies show clear differences in M1 plasticity between young and older adults, but many recent studies with motor training show no decline in use-dependent M1 plasticity with age. For NIBS-induced plasticity in M1, some protocols show more convincing differences with advancing age than others. Therefore, our view from the NIBS literature is that it should not be automatically assumed that M1 plasticity declines with age. Instead, the effects of age are likely to depend on how M1 plasticity is measured, and the characteristics of the elderly population tested. We also suggest that NIBS performed concurrently with motor training is likely to be most effective at producing improvements in M1 plasticity and motor skill learning in older adults. Proposed NIBS techniques for future studies include combining multiple NIBS protocols in a co-stimulation approach, or NIBS strategies to modulate intracortical inhibitory mechanisms, in an effort to more effectively boost M1 plasticity and improve motor skill learning in older adults.


Assuntos
Córtex Motor , Idoso , Encéfalo , Potencial Evocado Motor , Humanos , Plasticidade Neuronal , Estimulação Magnética Transcraniana
20.
Eur J Neurosci ; 54(6): 6123-6134, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34328240

RESUMO

This study examined the effect of temporal changes in corticospinal excitability in motor imagery (MI) and the effect of real-time guides for MI on excitability changes. The MI task involved wrist flexion and motor evoked potentials using transcranial magnetic stimulation were recorded and examined from the flexor carpi radialis. Ballistic (momentary MI) and tonic (continuous MI) conditions were used, and the duration of each MI was different. In Experiment 1, each MI task was performed using an acoustic trigger. In Experiment 2, a real-time guide was presented on a computer screen, which provided a visual indication of the onset and duration of the MI task through via moving dots on the screen. The results indicate that the corticospinal excitability changed differently, depending on the duration of MI. Additionally, with real-time guides, the change in corticospinal excitability became clearer. Thus, corticospinal excitability changes due to the temporal specificities of MI, as well as with actual motor output. Moreover, if MI is actively performed without a guide, it is likely to show an unintended change in corticospinal excitability. It is suggested that when MI is performed with visual guide, the excitatory changes of the corticospinal tract might be different from the actual motor output. Therefore, when using MI for mental practices, it is possible to improve the effect of a guide for MI, such as a visual indicator for motor output. Additionally, when examining neural activities in MI, it may be necessary to consider the characteristics of motion performed by MI.


Assuntos
Potencial Evocado Motor , Imaginação , Eletromiografia , Músculo Esquelético , Tratos Piramidais , Estimulação Magnética Transcraniana
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