Defence of doctoral thesis in the field of neuroscience and biomedical engineering, doctoral student Rasmus Zetter

Moving towards next-generation imaging of brain activity

Title of the doctoral thesis is "Development of an on-scalp MEG system using optically-pumped magnetometers"

Magnetoencephalography (MEG) is a noninvasive functional neuroimaging method in which the magnetic field caused by brain activity is measured using sensors outside the head. These neuromagnetic measurements are used to examine brain function both within neuroscientific research and clinical medicine.

Current state-of-the-art MEG systems utilize so-called SQUID sensors that require cryogenic cooling and thermal insulation between the sensors and the subject's head. The thermal insulation necessitates a relatively large brain–sensor separation, leading to loss of signal as well as spatial resolution. Recent developments to another type of sensor, called optically-pumped magnetometer (OPM), has resulted in sensors with sufficient performance for MEG use. OPMs do not require cryogenic cooling and can thus be placed much closer to, or even directly in contact with the subject's scalp. Such on-scalp MEG systems will significantly improve signal quality as well as increase spatial resolution, and may thus enable the detection of phenomena so far only detectable in invasive measurements that require surgery. In addition, the improved adaptability of OPMs will enable new types of MEG systems, including wearable MEG devices allowing for subject movement and smaller, low-cost systems.

This Thesis contributes to the development of an on-scalp MEG system based on OPMs and explores what such a system can or should consist of. Further, methods and software which can be utilized in the development of the next generation of on-scalp MEG systems are developed.

Through these works, this Thesis provides a stepping stone for the continued development of on-scalp MEG as an imaging method and demonstrates its future prospects.

Opponent: Professor Matthew Brookes, University of Nottingham, UK

Custos: Professor Lauri Parkkonen, Aalto University School of Science, Department of Neuroscience and Biomedical Engineering

Contact information of the doctoral candiate: Rasmus Zetter, Department of Neuroscience and Biomedical Engineering, [email protected], 0407475074

The defence will be organised remotely, via online platform. Link to the defence.

Zoom Guick Guide

The doctoral thesis will be publicly displayed 10 days before the defence on the publication archive of Aalto University (

Electronic doctoral thesis

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