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2.
Br J Sports Med ; 54(2): 110-115, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31420319

RESUMO

INTRODUCTION: The brain plays a key role in the perceptual regulation of exercise, yet neuroimaging techniques have only demonstrated superficial brain areas responses during exercise, and little is known about the modulation of the deeper brain areas at different intensities. OBJECTIVES/METHODS: Using a specially designed functional MRI (fMRI) cycling ergometer, we have determined the sequence in which the cortical and subcortical brain regions are modulated at low and high ratings perceived exertion (RPE) during an incremental exercise protocol. RESULTS: Additional to the activation of the classical motor control regions (motor, somatosensory, premotor and supplementary motor cortices and cerebellum), we found the activation of the regions associated with autonomic regulation (ie, insular cortex) (ie, positive blood-oxygen-level-dependent (BOLD) signal) during exercise. Also, we showed reduced activation (negative BOLD signal) of cognitive-related areas (prefrontal cortex), an effect that increased during exercise at a higher perceived intensity (RPE 13-17 on Borg Scale). The motor cortex remained active throughout the exercise protocol whereas the cerebellum was activated only at low intensity (RPE 6-12), not at high intensity (RPE 13-17). CONCLUSIONS: These findings describe the sequence in which different brain areas become activated or deactivated during exercise of increasing intensity, including subcortical areas measured with fMRI analysis.


Assuntos
Exercício/fisiologia , Córtex Motor/fisiologia , Adolescente , Adulto , Cerebelo/fisiologia , Córtex Cerebral/fisiologia , Ergometria/métodos , Humanos , Imagem por Ressonância Magnética , Masculino , Percepção/fisiologia , Esforço Físico/fisiologia , Córtex Pré-Frontal/fisiologia , Adulto Jovem
3.
Brain Lang ; 199: 104694, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31586790

RESUMO

The aim of the present study was to uncover a possible common neural organizing principle in spoken and written communication, through the coupling of perceptual and motor representations. In order to identify possible shared neural substrates for processing the basic units of spoken and written language, a sparse sampling fMRI acquisition protocol was performed on the same subjects in two experimental sessions with similar sets of letters being read and written and of phonemes being heard and orally produced. We found evidence of common premotor regions activated in spoken and written language, both in perception and in production. The location of those brain regions was confined to the left lateral and medial frontal cortices, at locations corresponding to the premotor cortex, inferior frontal cortex and supplementary motor area. Interestingly, the speaking and writing tasks also appeared to be controlled by largely overlapping networks, possibly indicating some domain general cognitive processing. Finally, the spatial distribution of individual activation peaks further showed more dorsal and more left-lateralized premotor activations in written than in spoken language.


Assuntos
Córtex Motor/fisiologia , Leitura , Percepção da Fala , Fala , Redação , Adulto , Mapeamento Encefálico , Feminino , Humanos , Imagem por Ressonância Magnética , Masculino
4.
Handb Clin Neurol ; 163: 237-255, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31590733

RESUMO

The prefrontal cortex serves a critical role in the coordination and execution of motor actions via its involvement in goal setting, decision-making, motivation, and cognitive control. Using the macaque connectome, the anatomic pathways from prefrontal cortex to motor circuitry are summarized, revealing a remarkably limited set of direct connections. A highly similar connectivity pattern is inferred from human neuroimaging. The results motivate the prefrontal-premotor connector hub model, which highlights both functional segregation and a limited set of connector hub regions that provide a direct linking of prefrontal cortex to the (pre-)motor network. Moreover, the macaque connectome reveals a set of motor translator regions that provide the most direct projection from premotor to prefrontal areas. The connector hub model leads to important functional implications: Neural activation or disruption in connector hubs should lead to functional deficits that undermine integration between higher cognitive action control and motor performance ranging from response selection and inhibition to perceived agency of actions. Segregation of prefrontal-premotor networks challenges hierarchical models of motor control and underscores the critical role of the indirect pathway from prefrontal to premotor areas via the parietal cortex. The model provides a predictive framework to design neurostimulation paradigms for modulating skill learning or recovery in both healthy subjects and patient cohorts.


Assuntos
Atividade Motora/fisiologia , Córtex Motor/fisiologia , Córtex Pré-Frontal/fisiologia , Desempenho Psicomotor/fisiologia , Mapeamento Encefálico , Humanos , Vias Neurais/fisiologia
5.
Nat Commun ; 10(1): 4812, 2019 10 23.
Artigo em Inglês | MEDLINE | ID: mdl-31645554

RESUMO

Neuronal networks of the mammalian motor cortex (M1) are important for dexterous control of limb joints. Yet it remains unclear how encoding of joint movement in M1 depends on varying environmental contexts. Using calcium imaging we measured neuronal activity in layer 2/3 of the M1 forelimb region while mice grasped regularly or irregularly spaced ladder rungs during locomotion. We found that population coding of forelimb joint movements is sparse and varies according to the flexibility demanded from individual joints in the regular and irregular context, even for equivalent grasping actions across conditions. This context-dependence of M1 encoding emerged during task learning, fostering higher precision of grasping actions, but broke apart upon silencing of projections from secondary motor cortex (M2). These findings suggest that M1 exploits information from M2 to adapt encoding of joint movements to the flexibility demands of distinct familiar contexts, thereby increasing the accuracy of motor output.


Assuntos
Membro Anterior , Força da Mão , Articulações/fisiologia , Locomoção/fisiologia , Córtex Motor/fisiologia , Neurônios/fisiologia , Animais , Camundongos , Córtex Motor/diagnóstico por imagem , Imagem Óptica , Optogenética , Amplitude de Movimento Articular
6.
PLoS Biol ; 17(10): e3000469, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31613874

RESUMO

Newly learned motor skills are initially labile and then consolidated to permit retention. The circuits that enable the consolidation of motor memories remain uncertain. Most work to date has focused on primary motor cortex, and although there is ample evidence of learning-related plasticity in motor cortex, direct evidence for its involvement in memory consolidation is limited. Learning-related plasticity is also observed in somatosensory cortex, and accordingly, it may also be involved in memory consolidation. Here, by using transcranial magnetic stimulation (TMS) to block consolidation, we report the first direct evidence that plasticity in somatosensory cortex participates in the consolidation of motor memory. Participants made movements to targets while a robot applied forces to the hand to alter somatosensory feedback. Immediately following adaptation, continuous theta-burst transcranial magnetic stimulation (cTBS) was delivered to block retention; then, following a 24-hour delay, which would normally permit consolidation, we assessed whether there was an impairment. It was found that when mechanical loads were introduced gradually to engage implicit learning processes, suppression of somatosensory cortex following training almost entirely eliminated retention. In contrast, cTBS to motor cortex following learning had little effect on retention at all; retention following cTBS to motor cortex was not different than following sham TMS stimulation. We confirmed that cTBS to somatosensory cortex interfered with normal sensory function and that it blocked motor memory consolidation and not the ability to retrieve a consolidated motor memory. In conclusion, the findings are consistent with the hypothesis that in adaptation learning, somatosensory cortex rather than motor cortex is involved in the consolidation of motor memory.


Assuntos
Potencial Evocado Motor/fisiologia , Retroalimentação Sensorial/fisiologia , Consolidação da Memória/fisiologia , Memória de Longo Prazo/fisiologia , Córtex Somatossensorial/fisiologia , Adolescente , Adulto , Feminino , Humanos , Masculino , Córtex Motor/anatomia & histologia , Córtex Motor/fisiologia , Destreza Motora/fisiologia , Plasticidade Neuronal/fisiologia , Córtex Somatossensorial/anatomia & histologia , Estimulação Magnética Transcraniana
7.
PLoS Biol ; 17(10): e3000480, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31613896

RESUMO

Many species execute ballistic escape reactions to avoid imminent danger. Despite fast reaction times, responses are often highly regulated, reflecting a trade-off between costly motor actions and perceived threat level. However, how sensory cues are integrated within premotor escape circuits remains poorly understood. Here, we show that in zebrafish, less precipitous threats elicit a delayed escape, characterized by flexible trajectories, which are driven by a cluster of 38 prepontine neurons that are completely separate from the fast escape pathway. Whereas neurons that initiate rapid escapes receive direct auditory input and drive motor neurons, input and output pathways for delayed escapes are indirect, facilitating integration of cross-modal sensory information. These results show that rapid decision-making in the escape system is enabled by parallel pathways for ballistic responses and flexible delayed actions and defines a neuronal substrate for hierarchical choice in the vertebrate nervous system.


Assuntos
Reação de Fuga/fisiologia , Córtex Motor/fisiologia , Neurônios Motores/fisiologia , Reconhecimento Fisiológico de Modelo/fisiologia , Ponte/fisiologia , Peixe-Zebra/fisiologia , Animais , Tomada de Decisões/fisiologia , Larva/fisiologia , Córtex Motor/citologia , Neurônios Motores/citologia , Ponte/citologia , Tempo de Reação/fisiologia
8.
Nat Commun ; 10(1): 4699, 2019 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-31619680

RESUMO

Regaining the function of an impaired limb is highly desirable in paralyzed individuals. One possible avenue to achieve this goal is to bridge the interrupted pathway between preserved neural structures and muscles using a brain-computer interface. Here, we demonstrate that monkeys with subcortical stroke were able to learn to use an artificial cortico-muscular connection (ACMC), which transforms cortical activity into electrical stimulation to the hand muscles, to regain volitional control of a paralysed hand. The ACMC induced an adaptive change of cortical activities throughout an extensive cortical area. In a targeted manner, modulating high-gamma activity became localized around an arbitrarily-selected cortical site controlling stimulation to the muscles. This adaptive change could be reset and localized rapidly to a new cortical site. Thus, the ACMC imparts new function for muscle control to connected cortical sites and triggers cortical adaptation to regain impaired motor function after stroke.


Assuntos
Adaptação Fisiológica/fisiologia , Interfaces Cérebro-Computador , Estimulação Elétrica , Córtex Motor/fisiopatologia , Músculo Esquelético/fisiologia , Córtex Somatossensorial/fisiopatologia , Acidente Vascular Cerebral/fisiopatologia , Animais , Braço , Córtex Cerebral/fisiologia , Córtex Cerebral/fisiopatologia , Eletrocorticografia , Mãos , Macaca mulatta , Córtex Motor/fisiologia , Vias Neurais/fisiopatologia , Paralisia , Córtex Somatossensorial/fisiologia , Reabilitação do Acidente Vascular Cerebral , Punho
9.
Elife ; 82019 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-31596230

RESUMO

Motor cortex (M1) has lateralized outputs, yet neurons can be active during movements of either arm. What is the nature and role of activity across the two hemispheres? We recorded muscles and neurons bilaterally while monkeys cycled with each arm. Most neurons were active during movement of either arm. Responses were strongly arm-dependent, raising two possibilities. First, population-level signals might differ depending on the arm used. Second, the same population-level signals might be present, but distributed differently across neurons. The data supported this second hypothesis. Muscle activity was accurately predicted by activity in either the ipsilateral or contralateral hemisphere. More generally, we failed to find signals unique to the contralateral hemisphere. Yet if signals are shared across hemispheres, how do they avoid impacting the wrong arm? We found that activity related to each arm occupies a distinct subspace, enabling muscle-activity decoders to naturally ignore signals related to the other arm.


Assuntos
Braço/inervação , Lateralidade Funcional , Córtex Motor/fisiologia , Neurônios Motores/fisiologia , Movimento , Animais , Macaca mulatta , Masculino
10.
PLoS Biol ; 17(10): e3000479, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31584933

RESUMO

Motor cortical beta activity (13-30 Hz) is a hallmark signature of healthy and pathological movement, but its behavioural relevance remains unclear. Using high-precision magnetoencephalography (MEG), we show that during the classical event-related desynchronisation (ERD) and event-related synchronisation (ERS) periods, motor cortical beta activity in individual trials (n > 12,000) is dominated by high amplitude, transient, and infrequent bursts. Beta burst probability closely matched the trial-averaged beta amplitude in both the pre- and post-movement periods, but individual bursts were spatially more focal than the classical ERS peak. Furthermore, prior to movement (ERD period), beta burst timing was related to the degree of motor preparation, with later bursts resulting in delayed response times. Following movement (ERS period), the first beta burst was delayed by approximately 100 milliseconds when an incorrect response was made. Overall, beta burst timing was a stronger predictor of single trial behaviour than beta burst rate or single trial beta amplitude. This transient nature of motor cortical beta provides new constraints for theories of its role in information processing within and across cortical circuits, and its functional relevance for behaviour in both healthy and pathological movement.


Assuntos
Ritmo beta/fisiologia , Sincronização Cortical/fisiologia , Potenciais Evocados/fisiologia , Córtex Motor/fisiologia , Movimento/fisiologia , Adulto , Feminino , Humanos , Magnetoencefalografia , Masculino , Córtex Motor/anatomia & histologia , Tempo de Reação/fisiologia
11.
Elife ; 82019 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-31612855

RESUMO

Prior expectations of movement instructions can promote preliminary action planning and influence choices. We investigated how action priors affect action-goal encoding in premotor and parietal cortices and if they bias subsequent free choice. Monkeys planned reaches according to visual cues that indicated relative probabilities of two possible goals. On instructed trials, the reach goal was determined by a secondary cue respecting these probabilities. On rarely interspersed free-choice trials without instruction, both goals offered equal reward. Action priors induced graded free-choice biases and graded frontoparietal motor-goal activity, complementarily in two subclasses of neurons. Down-regulating neurons co-encoded both possible goals and decreased opposite-to-preferred responses with decreasing prior, possibly supporting a process of choice by elimination. Up-regulating neurons showed increased preferred-direction responses with increasing prior, likely supporting a process of computing net likelihood. Action-selection signals emerged earliest in down-regulating neurons of premotor cortex, arguing for an initiation of selection in the frontal lobe.


Assuntos
Antecipação Psicológica , Comportamento de Escolha/fisiologia , Tomada de Decisões/fisiologia , Macaca mulatta/fisiologia , Córtex Motor/fisiologia , Lobo Parietal/fisiologia , Potenciais de Ação/fisiologia , Animais , Sinais (Psicologia) , Eletrodos Implantados , Funções Verossimilhança , Macaca mulatta/anatomia & histologia , Macaca mulatta/psicologia , Córtex Motor/anatomia & histologia , Neurônios Motores/citologia , Neurônios Motores/fisiologia , Movimento/fisiologia , Lobo Parietal/anatomia & histologia , Reconhecimento Visual de Modelos/fisiologia , Desempenho Psicomotor , Recompensa , Técnicas Estereotáxicas
12.
Elife ; 82019 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-31524600

RESUMO

Motor fatigability emerges when demanding tasks are executed over an extended period of time. Here, we used repetitive low-force movements that cause a gradual reduction in movement speed (or 'motor slowing') to study the central component of fatigability in healthy adults. We show that motor slowing is associated with a gradual increase of net excitability in the motor network and, specifically, in primary motor cortex (M1), which results from overall disinhibition. Importantly, we link performance decrements to a breakdown of surround inhibition in M1, which is associated with high coactivation of antagonistic muscle groups. This is consistent with the model that a loss of inhibitory control might broaden the tuning of population vectors such that movement patterns become more variable, ill-timed and effortful. We propose that the release of inhibition in M1 is an important mechanism underpinning motor fatigability and, potentially, also pathological fatigue as frequently observed in patients with brain disorders.


Assuntos
Fadiga , Mãos/fisiologia , Movimento , Adulto , Eletroencefalografia , Feminino , Voluntários Saudáveis , Humanos , Imagem por Ressonância Magnética , Masculino , Modelos Neurológicos , Córtex Motor/fisiologia , Adulto Jovem
13.
Phys Ther Sport ; 40: 143-152, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31546134

RESUMO

OBJECTIVE: The increase in voluntary force of an untrained limb (i.e. Cross-education) after unilateral resistance training (RT) is believed to be a consequence of cortical adaptations. However, studies measuring neurophysiological adaptations with transcranial magnetic stimulation (TMS) found inconsistent results. One unexamined factor contributing to the conflicting data is the variation in the type and intensity of muscle contractions, fatigue, and the strategies of pacing the movement. Therefore, the purpose was to analyse how those unilateral RT variables affect the adaptations in ipsilateral M1 (iM1) and cross-education. METHODS: We performed a systematic literature review, with the following search terms with Boolean conjunctions: "Transcranial magnetic stimulation" AND "Ipsilateral cortex" AND "Resistance training". RESULTS: The 11 acute and 12 chronic studies included partially support the idea of increased cortical excitability and reduced intracortical inhibition in iM1, but the inconsistency between studies was high. CONCLUSIONS: Differences in type and intensity of contraction, fatigue, and strategies of pacing the movement contributed to the inconsistencies. The tentative conclusion is that high intensity eccentric or externally paced contractions are effective to increase iM1 excitability but cross-education can occur in the absence of such changes. Thus, the mechanism of the cross-education examined with TMS remains unclear.


Assuntos
Excitabilidade Cortical , Córtex Motor/fisiologia , Contração Muscular , Treinamento de Resistência , Estimulação Magnética Transcraniana , Adaptação Fisiológica , Eletromiografia , Humanos , Músculo Esquelético/fisiologia
14.
Elife ; 82019 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-31490123

RESUMO

Cortico-basal ganglia-thalamocortical loops are largely conceived as parallel circuits that process limbic, associative, and sensorimotor information separately. Whether and how these functionally distinct loops interact remains unclear. Combining genetic and viral approaches, we systemically mapped the limbic and motor cortico-basal ganglia-thalamocortical loops in rodents. Despite largely closed loops within each functional domain, we discovered a unidirectional influence of the limbic over the motor loop via ventral striatum-substantia nigra (SNr)-motor thalamus circuitry. Slice electrophysiology verifies that the projection from ventral striatum functionally inhibits nigro-thalamic SNr neurons. In vivo optogenetic stimulation of ventral or dorsolateral striatum to SNr pathway modulates activity in medial prefrontal cortex (mPFC) and motor cortex (M1), respectively. However, whereas the dorsolateral striatum-SNr pathway exerts little impact on mPFC, activation of the ventral striatum-SNr pathway effectively alters M1 activity. These results demonstrate an open cortico-basal ganglia loop whereby limbic information could modulate motor output through ventral striatum control of M1.


Assuntos
Gânglios da Base/fisiologia , Sistema Límbico/fisiologia , Córtex Motor/fisiologia , Vias Neurais/fisiologia , Substância Negra/fisiologia , Animais , Gânglios da Base/anatomia & histologia , Fenômenos Eletrofisiológicos , Sistema Límbico/anatomia & histologia , Camundongos , Córtex Motor/anatomia & histologia , Vias Neurais/anatomia & histologia , Ratos , Substância Negra/anatomia & histologia
15.
Med Hypotheses ; 130: 109261, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31383345

RESUMO

There is a considerable amount of evidence sustaining that aerobic exercise causes positive modifications in gray matter density (GMD), especially in the hippocampus and anterior cingulate cortex. However, recent experimental researches with motor learning paradigms are consistently showing that increasing cardiorespiratory capacity is not the only mechanism able to promote positive outcomes in GMD with exercise. In the present study, we present a theoretical suggestion that expanding one's motor repertoire is another primary mechanism related to the increases in GMD. Motor repertoire can be understood as the number of movement possibilities and motor skills that can be performed by a person. Supporting our suggestion, professional athletes present higher GMD than controls, and experimental protocols repeatedly observes positive changes in GMD following motor learning. The relationship between physical inactivity, amputation, and lower GMD values also gives further support for the hypothesis. Follow-up studies monitoring GMD before and after training programs that stimulate new motor skill learning are essential to confirm this proposition. The brain regions related to sensory processing of the motor tasks and the cortical areas related to motor control (e.g., primary motor cortex, supplementary motor area) are probably the ones most affected by plastic changes. If the hypothesis turns out to be reliable, dancing, gymnastics, and other movement-rich activities are thoroughly encouraged for this purpose. Therefore, this approach might be used to attenuate GMD loss related to aging or another condition, such as Parkinson's and Alzheimer's.


Assuntos
Substância Cinzenta/fisiologia , Destreza Motora , Plasticidade Neuronal , Doença de Alzheimer/metabolismo , Cognição , Exercício , Hipocampo/metabolismo , Humanos , Modelos Neurológicos , Córtex Motor/fisiologia , Movimento , Doença de Parkinson/metabolismo , Resultado do Tratamento
16.
Brain Stimul ; 12(6): 1565-1571, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31383594

RESUMO

BACKGROUND: Obsessive-compulsive disorder (OCD) is a complex disorder with 40 to 60 % of patients resistant to treatment. Theta burst transcranial magnetic stimulation (TBS) is a promising new technique that has been shown to induce potent and long lasting effects on cortical excitability. The present study evaluated for the first time therapeutic efficacy and tolerability of continuous TBS (cTBS) over the supplementary motor area (SMA) in treatment resistant OCD patients using a double blind, sham-controlled design. METHODS: Thirty treatment resistant OCD outpatients were randomized to receive either active cTBS or sham cTBS for 6 weeks (5 sessions per week). Each treatment session consisted of 600 stimuli at an intensity of 70% of resting motor threshold. Patients were evaluated at baseline, at the end of treatment (week 6), and follow-up (week 12). Response to treatment was defined as at least 25% decrease on the Yale-Brown Obsessive Compulsive Scale. RESULTS: There was no significant difference between active and sham cTBS groups in treatment efficacy. Responder rates were not different between the two groups at week 6 (cTBS 28% versus sham 36%; p = 0.686) and week 12 (cTBS 28% versus sham 36%; p = 0.686). Depressive and anxious symptoms improvements were similar in the two groups. CONCLUSION: This study is the first controlled trial using cTBS in treatment resistant OCD patients. The use of cTBS over the SMA is safe but not sufficient to improve OCD symptoms. Further studies are needed to identify the optimal parameters to be used in OCD patients.


Assuntos
Córtex Motor/fisiologia , Transtorno Obsessivo-Compulsivo/psicologia , Transtorno Obsessivo-Compulsivo/terapia , Ritmo Teta/fisiologia , Estimulação Magnética Transcraniana/métodos , Adulto , Método Duplo-Cego , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Transtorno Obsessivo-Compulsivo/fisiopatologia , Resultado do Tratamento , Adulto Jovem
17.
Eur J Appl Physiol ; 119(10): 2185-2199, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31385029

RESUMO

PURPOSE: Transcranial magnetic stimulation (TMS) usually investigates the corticospinal responses of the agonist muscle to strength training, despite the role of the antagonist muscle in strength development. We examined the intracortical responses from an agonist and antagonist muscle following a single session of heavy-loaded strength training (dominant-arm only) to identify the early antagonistic responses to a single session that may accompany improvements in strength. METHODS: Corticospinal and motor cortical excitability and inhibition was collected from agonist and antagonist muscles prior to and following a single session of heavy-loaded wrist flexor training in 18 individuals. Training consisted of four sets 6-8 repetitions at 80% of 1-repetition maximum (1-RM). Recruitment curves for corticospinal excitability and inhibition of the right wrist flexor and wrist extensor muscles were constructed and assessed by examining the area under the recruitment curve. Intracortical measures were obtained using paired-pulse TMS. RESULTS: Following a single training session, increases in corticospinal excitability were observed in both the agonist and antagonist muscles. This was accompanied by decreases in corticospinal inhibition in both muscles. Intracortical inhibition was reduced and intracortical facilitation was increased for the agonist muscle only. Intracortical measures in the antagonist muscle remained unchanged after training. CONCLUSIONS: These findings indicate that the corticospinal responses to a single session of strength training are similar between agonist and antagonist muscles, but the intrinsic cortico-cortical circuitry of the antagonist remains unchanged. The corticospinal responses are likely due to increased involvement/co-activation of the antagonist muscle during training as the agonist muscle fatigues.


Assuntos
Excitabilidade Cortical , Córtex Motor/fisiologia , Músculo Esquelético/fisiologia , Inibição Neural , Condicionamento Físico Humano/métodos , Tratos Piramidais/fisiologia , Adulto , Feminino , Humanos , Masculino , Músculo Esquelético/inervação , Estimulação Magnética Transcraniana
18.
Brain Stimul ; 12(6): 1537-1552, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31377097

RESUMO

BACKGROUND: Transcranial magnetic stimulation (TMS) evokes voltage deflections in electroencephalographic (EEG) recordings, known as TMS-evoked potentials (TEPs), which are increasingly used to study brain dynamics. However, the extent to which TEPs reflect activity directly evoked by magnetic rather than sensory stimulation is unclear. OBJECTIVE: To characterize and minimize the contribution of sensory inputs to TEPs. METHODS: Twenty-four healthy participants received TMS over the motor cortex using two different intensities (below and above cortical motor threshold) and waveforms (monophasic, biphasic). TMS was also applied over the shoulder as a multisensory control condition. Common sensory attenuation measures, including coil padding and noise masking, were adopted. We examined spatiotemporal relationships between the EEG responses to the scalp and shoulder stimulations at sensor and source levels. Furthermore, we compared three different filters (independent component analysis, signal-space projection with source informed reconstruction (SSP-SIR) and linear regression) designed to attenuate the impact of sensory inputs on TEPs. RESULTS: The responses to the scalp and shoulder stimulations were correlated in both temporal and spatial domains, especially after ∼60 ms, regardless of the intensity and stimuli waveform. Among the three filters, SSP-SIR showed the best trade-off between removing sensoryrelated signals while preserving data not related to the control condition. CONCLUSIONS: The findings demonstrate that TEPs elicited by motor cortex TMS reflect a combination of transcranially and peripherally evoked brain responses despite adopting sensory attenuation methods during experiments, thereby highlighting the importance of adopting sensory control conditions in TMS-EEG studies. Offline filters may help to isolate the transcranial component of the TEP from its peripheral component, but only if these components express different spatiotemporal patterns. More realistic control conditions may help to improve the characterization and attenuation of sensory inputs to TEPs, especially in early responses.


Assuntos
Eletroencefalografia/métodos , Potencial Evocado Motor/fisiologia , Córtex Motor/fisiologia , Estimulação Magnética Transcraniana/métodos , Adolescente , Adulto , Feminino , Voluntários Saudáveis , Humanos , Masculino , Adulto Jovem
19.
Exp Brain Res ; 237(10): 2735-2746, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31435692

RESUMO

Repetitive transcranial magnetic stimulation combined with motor training (rTMS-MT) can be an effective method for enhancing motor function. However, the effects of rTMS-MT on inter-hemispheric lateralization remain unclear. Nineteen healthy volunteers were recruited. The volunteers were randomized to receive 2 weeks of rTMS-MT or MT to improve the motor function of the nondominant hand. Hand dexterity was tested by the Nine-Hole Peg Test. Resting motor threshold (RMT), motor evoked potentials (MEP) and electroencephalography (EEG) in the resting state with eyes closed were recorded, to calculate inter-hemispheric lateralization before and after rTMS-MT or MT. rTMS-MT and MT improved the dexterity and MEP amplitude of the nondominant hand. Furthermore, there were significant changes in the lateralization of not only power spectral density, but also information transmission efficiency between regions following rTMS-MT, especially between the central cortices of both hemispheres. However, although the lateralization change of the power spectral density between the central cortices was observed following MT, there was no such change for information transmission efficiency between any cortices. These results suggested that rTMS-MT could modulate inter-hemispheric lateralization. Changes in inter-hemispheric lateralization might be an important neural mechanism by which rTMS-MT improves motor function. These results could be helpful for understanding the brain mechanism of rTMS-MT.


Assuntos
Potencial Evocado Motor/fisiologia , Atividade Motora/fisiologia , Córtex Motor/fisiologia , Estimulação Magnética Transcraniana , Adulto , Encéfalo/fisiologia , Eletroencefalografia/métodos , Feminino , Humanos , Masculino , Descanso/fisiologia , Estimulação Magnética Transcraniana/métodos , Adulto Jovem
20.
Brain Stimul ; 12(6): 1381-1389, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31405789

RESUMO

Over the past decade several studies have shown that transcranial alternating current stimulation (tACS) delivered at the beta (15-25 Hz) frequency range can increase corticospinal excitability of the primary motor cortex (M1). The aim of this study was to systematically quantify the effect size of beta-tACS on corticospinal excitability in healthy volunteers, as well as to identify significant outcome predictors. A meta-analysis was performed on the results of 47 experiments reported in 21 studies. Random effects modelling of the effect sizes showed that beta-tACS significantly increases M1 excitability (E = 0.287, 95% CI = 0.133-0.440). Further analysis showed that tACS intensities above 1 mA peak-to-peak yield a robust increase in M1 excitability, whereas intensities of 1 mA peak-to-peak and below do not induce a reliable change. Additionally, results showed an impact of tACS montages on these effects. No difference in effect size for online compared to offline application of tACS was found. In conclusion, these findings indicate that beta-tACS can increase cortical excitability if stimulation intensity is above 1 mA, yet more research is needed to titrate the stimulation parameters that yield optimal results.


Assuntos
Excitabilidade Cortical/fisiologia , Potencial Evocado Motor/fisiologia , Córtex Motor/fisiologia , Tratos Piramidais/fisiologia , Estimulação Transcraniana por Corrente Contínua/métodos , Humanos , Estimulação Transcraniana por Corrente Contínua/tendências
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