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. 2020 Feb 18;14:5. doi: 10.3389/fnint.2020.00005

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Copyright © 2020 Bhattacharjee, Kajal, Patrono, Li Hegner, Zampini, Schwarz and Braun.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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To investigate the noise introduced by the tactile virtual reality device, power spectra during operation of the device (red) were compared to the spectra of the empty room (black). The application of 3rd order software gradiometers (cyan) reduced the power in frequency bands related to the operation of the virtual reality device (600 Hz and harmonics). To mimic the movement of the device by the participant during operation, the scanning probe was pushed onto and released from the touchpad via a pneumatic mechanism with a frequency of 1 Hz. The power spectrum during the simulated operation was compared to the noise level of the empty measurement chamber. The MEG measuring the noise spectra consists of three types of magnetic field sensors: (1) MEG first-order axial gradiometers having a baseline of 5 cm are placed in the helmet of the MEG-device and are designed to register participants brain activity. (2) Reference gradiometers (REF Gradiometer) which have a baseline of 2 cm and are placed about 5 cm above the helmet, are used for sensing distant sources of noise. (3) Similarly, reference magnetometers (Ref Magnetometer) located next to the reference gradiometer are also used for noise cancellation. Since reference gradiometers and reference magnetometers are further away from the subject’s brain, they record predominantly environmental noise activity.