Most people are probably familiar with fMRI, the large magnetic tube, which is used to reveal the location of injuries in the brain. Whil fMRI provides excellent information on the location of neural activity, the temporal resolution is several seconds. Our brain, however, functions on a milisecond timescale.

This is why electrophysiological brain imaging is so important. While localisation of brain activity is limited, EEG, MEG and OPMs can provide data of brain activity at milisecond precision. Oftentimes a combination of both methods provides the best result.

The Electroencephalogram (EEG) records electrical currents transmitted from their neural origin to the scalp. These currents are very small and might just be cloaked by electrical activity of muscles (small movements like chewing). This is why while measuring EEG, you have to sit very still and even limit eye movement or blinking. The magnetoencephalogram (MEG) on the other hand, measures magnetic fields elicited bei neuronal activity. Both methods usually lead to similar results, however, MEG is less prone to artifacts through slight movements. However, MEG so far requires a large, stationary device, which requires consistent and expensive cooling and is often only available in one size – usually excluding the possibility to measure children. Accordingly, MEG is not widely available in research and clinical settings.

A new and exciting development in the field are optically pumped magnetometers (OPMs). They also measure magnetic activity elicited by neurons in our brain. However, they are small and do not require cooling, introducing new opportunities. They can be adapted to fit any person, including children. They are even less prone to movement artifacts than common MEG. Additionally, they can be positioned closer to the head, which increases the sensitivity of measurement.