Simultaneous magnetic brain stimulation and measurement

Project Information

STIMUSURE

Grant agreement ID: 101027633

DOI

10.3030/101027633

Project closed

EC signature date 14 April 2021

Start date 18 August 2021

End date 15 February 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 224 933,76

EU contribution

€ 224 933,76

Coordinated by

THE UNIVERSITY OF BIRMINGHAM
United Kingdom

Periodic Reporting for period 1 - STIMUSURE (Simultaneous magnetic brain stimulation and measurement)

Reporting period: 2021-08-18 to 2023-08-17

Summary of the context and overall objectives of the project

STIMUSURE aimed to develop the first magnetoencephalography (MEG) sensor compatible with simultaneous transcranial magnetic stimulation (TMS). TMS is the most precise non-invasive brain stimulation method, and MEG is the most precise non-invasive brain recording technique. Combining the two would allow for more precise functional brain imaging and enable development of tools that would help us understand the functional connectivity between brain regions.

STIMUSURE developed an optically pumped magnetometer (OPM) sensor prototype for MEG. The developed sensor could both withstand TMS pulses (peak magnetic field 10,000 times the Earth’s magnetic field) and record weak magnetic brain magnetic fields (typical magnetic field less than 1/100,000,000 times the Earth's magnetic field, or about one trillionth of the peak field during TMS).

The project, however, could not reach the aim of recording MEG signal from the human brain shortly after TMS pulses as the residual magnetic fields of the TMS coil could not be reduced by the required factor of 1,000,000,000,000 sufficiently fast, taking over 0.05 s rather than the desired below 0.01 s to suppress the residual field after each TMS pulse. To solve this technical limitation would require development of better TMS hardware. The project did, however, result in the first intrinsic optically pumped magnetic gradiometer for human use.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

STIMUSURE developed a computational model for TMS in a magnetically shielded room and validated these models experimentally with a STIMUSURE-developed custom search-coil magnetometer.

STIMUSURE developed computational models to optimise both single OPM sensors and multi-sensor arrays for OPM-MEG. The first computational model was published in a journal article, and the results from the second model were presented in a conference talk in the WOPM 2023 meeting, respectively.

STIMUSURE developed an ultra-sensitive magnetic field sensor that can also tolerate extremely strong magnetic field pulses. STIMUSURE enabled this by the developing a method to design and build miniaturised self-shield magnetic field coils with a high shielding factor. Beyond these coils, STIMUSURE developed a compact electro-optomechanical assembly for an OPM-MEG sensor head, and then repurposed this design also to develop the first intrinsic optically pumped magnetic gradiometer for human biomagnetism. In this application, the self-shielded coils shielded the two halves of the gradiometer sensor from each other.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

STIMUSURE developed a method to design and build high-quality miniaturised self-shielded coils with very high shielding factors, enabling the development of the first intrinsic optically pumped magnetic gradiometer.

A computer-generated image to illustrate the internals of the optically pumped magnetic gradiometer.