Paired-pulse transcranial magnetic stimulation: development of new methods for motor cortex mapping and cortical excitability

• Grant number: 24/07674-1
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: June 01, 2024
• End date: May 31, 2025
• Field of knowledge: Physical Sciences and Mathematics - Physics
• Principal Investigator: Oswaldo Baffa Filho
• Grantee: Thais Cunha Marchetti
• Host Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Associated research grant: 13/07699-0 - Research, Innovation and Dissemination Center for Neuromathematics - NeuroMat, AP.CEPID

Abstract

Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique used for brain investigation, playing an important role in motor mapping. One modality of TMS is paired-pulse TMS, where pulses are delivered in pairs with controlled intensities and temporal differences. Depending on the time interval between pulses, motor inhibition or facilitation can be observed, as seen through the variation in the amplitude of the obtained motor evoked responses (Zewdie and Kirton 2016). Motor mapping protocols with TMS are usually based on single-pulse applications. However, paired-pulse motor mappings have proven to be more efficient for patients with motor impairment, leading to similar motor maps but with the capability to evoke responses with lower stimulus intensities (Sollmann et al. 2020). Since the cortical representation of muscles depends on the stimulation intensity used (Tardelli et al. 2022) and the precision of stimulator positioning (Matsuda et al. 2024), the possibility of reducing stimulus intensity with paired pulses combined with a robotic neuronavigation system for stimulator positioning can be a promising tool for motor mapping. Therefore, in this project, we propose to explore paired-pulse TMS to improve the specificity of motor mapping, resulting in more delineated cortical muscle representation areas. Additionally, we propose to explore pairing with contralateral targets based on different anatomical criteria, such as anatomical MRI and diffusion-weighted images.