Name: Registros eletromiográficos usando um olfatômetro sincronizado com respiração com EMT
Uploaded: 2024-01-19T13:10:00
Description: Watch this Scientific Journal Video about Electromyography Recordings Using a Breath-Synchronized Olfactometer with TMS at JoVE.com

electromyography recordings using a breath-synchronized olfactometer with tms

Effect of Odor on Brain Excitability Assessed by a Breath-Synchronized Olfactometer

It is widely accepted that olfactory stimulation elicits automatic reactions and motor behaviors. For example, in humans, the existence of an avoidance motor response (leaning away from the odor source) occurring 500 ms after negative odor onset has been recently demonstrated1. By recording freely moving human participants exploring odors emanating from flasks, Chalen&#231;on et al. (2022) showed that motor behaviors (i.e., speed of approach to the nose and withdrawal of the flask containing the odorant) are closely linked to odor hedonics2. Moreover, a close link between processing in the olfactory system and activity in the motor cortex has been recently demonstrated in humans by using electroencephalography1. Specifically, approximately 350 ms after the onset of negative odors, a specific mu rhythm desynchronization, known to reflect action preparation processes, was observed over and within the primary motor cortex (M1), shortly followed by a behavioral backward movement1. Strengthening the idea of a relationship between the olfactory and motor systems, another recent study showed that exposure to a pleasant odorant increased corticospinal excitability compared to a no-odor condition3. In this study, single-pulse transcranial magnetic stimulation (spTMS) was applied to M1 to evoke a motor-evoked potential (MEP) in a target hand muscle, recorded peripherally with electromyography (EMG) during odor perception. Exposure to the pleasant odorant was provided passively&#160;by paper strips sodden with pure bergamot essential oil and placed on a metal holder under the nose3. In this context, it remains unclear whether the facilitation of the corticospinal excitability is due to the pleasant odorant stimulation or to unspecific behavioral effects such as sniffing and teeth clenching4,5. Furthermore, it is still unknown how an unpleasant odorant modulates M1 excitability probed by TMS.
In summary, this highlights the need to develop a method that offers the following advantages over existing techniques used in previous studies3,6: (1) randomizing the presentation of different odor conditions (pleasant/unpleasant/no-odor) within the same experimental phase, (2) precisely synchronizing odorant presentation and TMS timing according to the human nasal breathing phases (inspiration and expiration) when studying the motor system.
TMS can also be used as a tool to investigate cortico-cortical interactions, also called effective connectivity, between multiple cortical areas and M1 with a high temporal resolution7,8,9,10,11,12. Here, we use a dual-site TMS (dsTMS) paradigm, in which a first-conditioning stimulation (CS) activates a target cortical area, and a second-test stimulation (TS) is applied over M1 using another coil to evoke an MEP. The effect of the CS is evaluated by normalizing the amplitude of the conditioned MEP (dsTMS condition) to the amplitude of the unconditioned MEP (spTMS condition)13. Then, negative ratio values indicate&#160;suppressive cortico-cortical interactions, while positive ratio values indicate facilitatory cortico-cortical interactions between the two stimulated areas. The dsTMS paradigm thus provides a unique opportunity to identify the nature (i.e., facilitatory or suppressive), the strength, and the modulations of the effective connectivity between the preactivated area and M1. Importantly, cortico-cortical interactions reflect a complex balance of facilitation and suppression that may be modulated in different timing and mental states or tasks7,14.
To our knowledge, the relatively new dsTMS paradigm has never been used to investigate cortico-cortical interactions during odor perception with different hedonic values. However, neuroimaging studies have shown that exposure to pleasant and unpleasant odorants induces connectivity changes in areas involved in emotion, decision-making, and action control, including the supplementary motor area, the anterior cingulate cortex, and the dorsolateral prefrontal cortex (DLPFC)15,16. Indeed, the DLPFC is a key node mediating emotional control, sensory processing, and higher-level aspects of motor control, such as preparatory processes17,18,19. In addition, both human and animal studies have provided evidence that the DLPFC has diverse neuronal projections to M117,18,20,21,22. Depending on the context, these DLPFC projections can either facilitate or inhibit M1 activity7,19,20. Thus, it seems possible that the effective connectivity between DLPFC and M1 is modulated during odor presentation and that pleasant and unpleasant odorants recruit separated cortical networks, leading to a differential effect on DLPFC-M1 connectivity.
Here, we propose a new method suitable for the methodologically rigorous study of the modulations of corticospinal excitability and effective connectivity that might occur during the perception of pleasant and unpleasant odors, all delivered in synchrony with human nasal breathing.

Author Spotlight: Exploring Olfactory Influences on Corticospinal Excitability - Insights and Innovations in Neurological Research 

Combinando um Olfatômetro Sincronizado com a Respiração com Simulação Cerebral para Estudar o Impacto dos Odores na Excitabilidade Corticoespinhal e Conectividade Eficaz

Watch this Scientific Journal Video about Electromyography Recordings Using a Breath-Synchronized Olfactometer with TMS at JoVE.com

Registros eletromiográficos usando um olfatômetro sincronizado com respiração com EMT

Para começar, peça ao participante que se sente em uma cadeira confortável, com as duas mãos relaxadas e pronadas. Antes da aplicação do eletrodo, prepare a pele do participante usando um esfoliante para abrasar levemente as áreas. Limpe as áreas com compressas de álcool onde serão aplicados eletrodos.Em seguida, aplique dois eletrodos de registro descartáveis de prata/cloreto de prata usando uma montagem ventre-tendão para o primeiro músculo interósseo dorsal. Coloque o eletrodo terra no processo estiloide da ulna. Conecte os eletrodos ao amplificador com cabos.Integre o sistema com o sistema de aquisição de dados. Gravar o sinal EMG e avaliar a qualidade do sinal exibido na tela conectada ao sistema de aquisição de dados. Em seguida, conecte a bobina M1 do TMS ao estimulador A.Em seguida, coloque uma touca apertada sobre a cabeça do participante. Use uma fita métrica para realizar medidas de nasion-ínion, tragus-tragus e perímetro cefálico com base em pontos de referência cranianos padrão. Identificar o vértice do couro cabeludo na intersecção das linhas sagital média e intraoral e marcá-lo com caneta.Em seguida, coloque a primeira pequena figura de oito bobinas tangencialmente ao couro cabeludo sobre a suposta área da mão do M1 esquerdo, que fica cinco centímetros lateral do vértice. Em seguida, conecte o DLPFC da bobina TMS ao estimulador B. Use a heurística atualizada do couro cabeludo para localizar a região do couro cabeludo correspondente à CPFDL esquerda.Estimar a posição da segunda pequena figura de oito bobinas sobre o DLPFC. Baixe a ferramenta de cálculo de planilha Excel online. Insira as distâncias nasion-inion e tragus-tragus e o perímetro cefálico em centímetros.Relate as distâncias XLA e YLA diretamente na cabeça do participante. Coloque a bobina de EMT DLPFC tangencialmente ao couro cabeludo sobre a suposta localização do CPFDL esquerdo com a alça apontando para baixo e lateralmente em um ângulo de menos 45 graus em relação à linha sagital média. Marque a colocação do DLPFC da bobina TMS na tampa para garantir a colocação adequada da bobina durante todo o experimento.Em seguida, colocar a cânula nasal do olfatômetro próximo às narinas do participante para mensuração da respiração nasal. Instruir o participante a respirar normalmente pelo nariz. Ligue o compressor de ar portátil, a caixa do olfatômetro e o PC que contém o software.Verifique todas as conexões de cabo. Prosseguir para a fase de calibração por 20 segundos para ajustar os limiares de detecção das fases expiratória e inspiratória. Execute o script de codificação personalizado no software olfatômetro para entregar todas as combinações de SPTMS e DSTMS com odores agradáveis e desagradáveis e sem odores ocorrendo em uma ordem aleatória.Um gráfico representativo dos sinais respiratórios mostrou que as fases expiratória e inspiratória são detectadas ao cruzar o limiar. O odorante disparou imediatamente após o limiar de fase expiratória e o pulso de EMT desencadeou com um atraso após o limiar de fase inspiratória, demonstrando que este método pode sincronizar com precisão a difusão do odorante e o tempo de EMT de acordo com as fases da respiração nasal humana. Os registros EMG e PEmáx dos músculos IDE direitos mostraram que a amplitude pico-a-pico dos PEmáx evocados pelo TMSP e pelo DSTMS variou de acordo com o valor hedonístico do odorante.Quando os resultados foram normalizados, todas as razões PEmáx estavam abaixo de um, indicando um efeito supressor do CPFDL esquerdo no M1 esquerdo.

Research

JoVE Journal

Neuroscience

Electromyography Recordings Using a Breath-Synchronized Olfactometer with TMS

Combining a Breath-Synchronized Olfactometer with Brain Simulation to Study the Impact of Odors on Corticospinal Excitability and Effective Connectivity

It is widely accepted that olfactory stimulation elicits motor behaviors, such as approaching pleasant odorants and avoiding unpleasant ones, in animals ...