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Retrieving context tree models driven by structured TMS pulse sequences applied in the primary motor cortex.

Grant number: 22/00582-9
Support Opportunities:Scholarships in Brazil - Post-Doctoral
Effective date (Start): May 01, 2022
Effective date (End): April 30, 2024
Field of knowledge:Physical Sciences and Mathematics - Probability and Statistics - Applied Probability and Statistics
Principal Investigator:Antonio Carlos Roque da Silva Filho
Grantee:Bia Ramalho dos Santos Lima
Host Institution: Instituto de Matemática e Estatística (IME). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:13/07699-0 - Research, Innovation and Dissemination Center for Neuromathematics - NeuroMat, AP.CEPID


The transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique based on electromagnetic induction. A single TMS pulse in the primary motor cortex produces motor evoked potentials (MEPs) that can be measured in muscles of interest through electromyography (EMG), but also TMS-evoked potentials (TEPs) that can be recorded in the cerebral cortex using electroencephalography (EEG). Differences in TMS stimulus intensity, coil orientation and the time interval between two pulses were shown to modulate the MEPs and TEPs responses, revealing that MEP and TEP are non-stereotypical responses (sensitive to stimulus parameters change), reflecting deterministic properties of the stimulated set of cortical neurons. TMS-EEG protocols may be employed to detect longitudinal changes in the state of cortical circuits, emerging as an interesting method for investigating cortical dynamics. Therefore, the goal of the present project is to investigate whether the primary motor cortex holds a memory of a sequence of TMS pulses varying following a context tree. If so, it should be possible to recover in the MEP and TEPs response signatures of a sequence of TMS pulses applied in the primary motor cortex. This approach was inspired by the NeuroMat previous work of Duarte et al. (2019) and Hernandez et al. (2021), who submitted subjects to a sequence of auditory stimuli while their electroencephalographic signals (EEG) were recorded. They used a stochastic chain with memory of variable length to model the dependence from the past characterizing the sequence of auditory stimuli. Therefore, we expect to retrieve in the MEP responses and the TEPs the context tree used to produce the sequence of stimuli, indicating that the brain acquires a memory of the sequence of pulses.

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
MORAES, VICTOR HUGO; VARGAS, CLAUDIA D.; RAMALHO, BIA L.; MATSUDA, RENAN H.; SOUZA, VICTOR H.; IMBIRIBA, LUIS AURELIANO; GARCIA, MARCO ANTONIO C.. Effect of muscle length in a handgrip task on corticomotor excitability of extrinsic and intrinsic hand muscles under resting and submaximal contraction conditions. SCANDINAVIAN JOURNAL OF MEDICINE & SCIENCE IN SPORTS, v. N/A, p. 10-pg., . (22/00582-9, 13/07699-0, 22/14526-3)

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