Influence of Magnetic Fields and their Characteristics on cortical Excitability. Study on healthy adults and pathological aging

Programa Oficial de Doutoramento en Neurociencias. 5028V01[Resumen] Esta tesis doctoral pretende responder dos cuestiones relacionadas con la interacción de los campos magnéticos dinámicos y estáticos con el córtex motor. En los dos primeros experimentos se estudiaron factores que influyen en la reproducibilidad de la estimulación magnética transcraneal (TMS). Estas investigaciones demostraron que los efectos y la reproducibilidad de la TMS se ven afectados por dos tipos de factores relevantes: (1) factores técnicos o modificables, en particular la forma de onda y dirección de corriente de los pulsos de la TMS; y (2) factores fisiológicos, en concreto la influencia del envejecimiento fisiológico y de enfermedades relacionadas con el envejecimiento, como la demencia por enfermedad de Alzheimer y la Diabetes Mellitus tipo 2. En un segundo tipo de estudio se observó que la estimulación magnética estática transcraneal (tSMS) produce una reducción de la excitabilidad y reactividad del sistema motor. Sin embargo, esta reducción sólo se pudo captar por un tipo específico de forma de onda de TMS, indicando que la acción de la tSMS se centra sobre redes interneurales específicas. En los registros electroencefalográficos se cuantificó un aumento de las frecuencias del rango beta en regiones fronto-centrales, que está inversamente correlacionado con la disminución de la excitabilidad.[Resumo] Esta tese de doutoramento pretende responder dúas cuestións relacionadas coa interacción dos campos magnéticos dinámicos e estáticos co córtex motor. Nos dous primeiros experimentos estudáronse factores que inflúen na reproducibilidade da estimulación magnética transcraneal (TMS). Estas investigacións demostraron que tanto os efectos como a reproducibilidade da TMS vense afectados por dous tipos de factores relevantes: (1) factores técnicos ou modificables, en particular a forma de onda e a dirección da corrente dos pulsos da TMS; e (2) factores fisiolóxicos, en concreto a influencia do envellecemento fisiolóxico e as enfermidades relacionadas co envellecemento, coma a demencia por enfermidade de Alzheimer e a Diabetes Mellitus tipo 2. Nun segundo tipo de estudo observouse que a estimulación magnética estática transcraneal (tSMS) produce unha redución da excitabilidade e reactividade do sistema motor. Porén, esta redución só puido ser capturada por un tipo específico de forma de onda de TMS, o que indica que a acción da tSMS céntrase en redes interneurais específicas. Nos rexistros electroencefalográficos cuantificouse un aumento das frecuencias do rango beta nas rexións fronto-centrais, que está inversamente correlacionado coa diminución da excitabilidade.[Abstract] This doctoral thesis intended to answer two questions in relation to the interaction between dynamic and static magnetic fields, and the motor cortex. During the first two experiments, we studied factors that influence the reproducibility of transcranial magnetic stimulation (TMS). These investigations have shown that two types of relevant factors impact the effects and the reproducibility of the TMS: (1) technical or modifiable factors, in particular the TMS pulse waveform and current direction; and (2) physiological factors, specifically the influence of physiological aging and age-related diseases, such as Dementia due to Alzheimer's disease and type 2 Diabetes Mellitus. In a second type of study, a reduction of motor cortex excitability and reactivity was observed after applying transcranial static magnetic stimulation (tSMS). However, this reduction was only captured by a specific type of TMS waveform, indicating that the action of the tSMS is centered on specific cortical interneuron networks. Electroencephalographic recordings quantified an increase in the range of beta frequencies in fronto-central regions, this increase was negatively correlated with the reduction in cortical excitability

The effects of waveform and current direction on the efficacy and test–retest reliability of transcranial magnetic stimulation

[Abstract] The pulse waveform and current direction of transcranial magnetic stimulation (TMS) influence its interactions with the neural substrate; however, their role in the efficacy and reliability of single- and paired-pulse TMS measures is not fully understood. We investigated how pulse waveform and current direction affect the efficacy and test–retest reliability of navigated, single- and paired-pulse TMS measures. 23 healthy adults (aged 18–35 years) completed two identical TMS sessions, assessing resting motor threshold (RMT), motor-evoked potentials (MEPs), cortical silent period (cSP), short- and long-interval intra-cortical inhibition (SICI and LICI), and intracortical facilitation (ICF) using either monophasic posterior–anterior (monoPA; n = 9), monophasic anterior–posterior (monoAP; n = 7), or biphasic (biAP-PA; n = 7) pulses. Averages of each TMS measure were compared across the three groups and intraclass correlation coefficients were calculated to assess test–retest reliability. RMT was the lowest and cSP was the longest with biAP-PA pulses, whereas MEP latency was the shortest with monoPA pulses. SICI and LICI had the largest effect with monoPA pulses, whereas only monoAP and biAP-PA pulses resulted in significant ICF. MEP amplitude was more reliable with either monoPA or monoAP than with biAP-PA pulses. LICI was the most reliable with monoAP pulses, whereas ICF was the most reliable with biAP-PA pulses. Waveform/current direction influenced RMT, MEP latency, cSP, SICI, LICI, and ICF, as well as the reliability of MEP amplitude, LICI, and ICF. These results show the importance of considering TMS pulse parameters for optimizing the efficacy and reliability of TMS neurophysiologic measures

Influencia de variables organizacionales en la calidad de vida laboral de funcionarios del sector público de salud en el extremo norte de Chile

We describe the Quality of Working Life and its relationship with the Organizational Climate, Job Satisfaction and Engagement in officials of public health organization in the city of Arica, Chile. 142 adult subjects of both sexes. We used the Inventory of Quality of Work Life, Organizational Climate Inventory, Job Satisfaction Questionnaire S21/26, and Engagement Questionnaire. The results show a significant relationship between the quality of working life and organizational variables measures, noting the presence of significant differences in the Quality of Working Life in terms of establishment of civil administration. Jointly, we found that the variable Engagement modulates the relation between Quality of Working Life, organizational climate and job satisfaction. These results demonstrate the association between organizational and interpersonal variables that come together in the workplace, with subjective assessments that subjects build on the characteristics of their work environment, modulating their involvement and productivity.En el presente estudio se describe la calidad de vida laboral y su relación con el clima organizacional, la satisfacción laboral y el engagement en funcionarios de organizaciones públicas de salud de la ciudad de Arica, Chile. Participaron 142 sujetos de ambos sexos. Se utilizaron el Inventario de Calidad de Vida Laboral, el Inventario de Clima Organizacional, el Cuestionario de Satisfacción Laboral S21/26 y el Cuestionario de Engagement. Los resultados muestran una relación significativa entre la calidad de vida laboral y las variables organizacionales medidas, observando la presencia de diferencias significativas en función del estamento administrativo de los funcionarios. Conjuntamente, se encontró que la variable engagement modula la relación entre la calidad de vida laboral, clima organizacional y satisfacción laboral. Estos resultados evidencian la asociación entre las variables organizacionales e interpersonales que confluyen en el ámbito laboral con las valoraciones subjetivas que los sujetos construyen sobre las características de su entorno de trabajo, modulando su implicación y productividad

Reproducibility of Single-Pulse, Paired-Pulse, and Intermittent Theta-Burst TMS Measures in Healthy Aging, Type-2 Diabetes, and Alzheimer’s Disease

Background: Transcranial magnetic stimulation (TMS) can be used to assess neurophysiology and the mechanisms of cortical brain plasticity in humans in vivo. As the use of these measures in specific populations (e.g., Alzheimer’s disease; AD) increases, it is critical to understand their reproducibility (i.e., test–retest reliability) in the populations of interest. Objective: Reproducibility of TMS measures was evaluated in older adults, including healthy, AD, and Type-2 diabetes mellitus (T2DM) groups. Methods: Participants received two identical neurophysiological assessments within a year including motor thresholds, baseline motor evoked potentials (MEPs), short- and long-interval intracortical inhibition (SICI, LICI) and intracortical facilitation (ICF), and MEP changes following intermittent theta-burst stimulation (iTBS). Cronbach’s α coefficients were calculated to assess reproducibility. Multiple linear regression analyses were used to investigate factors related to intraindividual variability. Results: Reproducibility was highest for motor thresholds, followed by baseline MEPs, SICI and LICI, and was lowest for ICF and iTBS aftereffects. The AD group tended to show higher reproducibility than T2DM or controls. Intraindividual variability of baseline MEPs was related to age and variability of RMT, while the intraindividual variability in post-iTBS measures was related to baseline MEP variability, intervisit duration, and Brain-derived neurotrophic factor (BDNF) polymorphism. Conclusion: Increased reproducibility in AD may reflect pathophysiological declines in the efficacy of neuroplastic mechanisms. Reproducibility of iTBS aftereffects can be improved by keeping baseline MEPs consistent, controlling for BDNF genotype, and waiting at least a week between visits. Significance: These findings provide the first direct assessment of reproducibility of TMS measures in older clinical populations. Reproducibility coefficients may be used to adjust effect- and sample size calculations for future studies

Influencia de variables organizacionales en la calidad de vida laboral de funcionarios del sector público de salud en el extremo norte de Chile

We describe the Quality of Working Life and its relationship with the Organizational Climate, Job Satisfaction and Engagement in officials of public health organization in the city of Arica, Chile. 142 adult subjects of both sexes. We used the Inventory of Quality of Work Life, Organizational Climate Inventory, Job Satisfaction Questionnaire S21/26, and Engagement Questionnaire. The results show a significant relationship between the quality of working life and organizational variables measures, noting the presence of significant differences in the Quality of Working Life in terms of establishment of civil administration. Jointly, we found that the variable Engagement modulates the relation between Quality of Working Life, organizational climate and job satisfaction. These results demonstrate the association between organizational and interpersonal variables that come together in the workplace, with subjective assessments that subjects build on the characteristics of their work environment, modulating their involvement and productivity.En el presente estudio se describe la calidad de vida laboral y su relación con el clima organizacional, la satisfacción laboral y el engagement en funcionarios de organizaciones públicas de salud de la ciudad de Arica, Chile. Participaron 142 sujetos de ambos sexos. Se utilizaron el Inventario de Calidad de Vida Laboral, el Inventario de Clima Organizacional, el Cuestionario de Satisfacción Laboral S21/26 y el Cuestionario de Engagement. Los resultados muestran una relación significativa entre la calidad de vida laboral y las variables organizacionales medidas, observando la presencia de diferencias significativas en función del estamento administrativo de los funcionarios. Conjuntamente, se encontró que la variable engagement modula la relación entre la calidad de vida laboral, clima organizacional y satisfacción laboral. Estos resultados evidencian la asociación entre las variables organizacionales e interpersonales que confluyen en el ámbito laboral con las valoraciones subjetivas que los sujetos construyen sobre las características de su entorno de trabajo, modulando su implicación y productividad