306 channel whole head system

MEG was recorded in a magnetically shielded room (JFE Mechanical Co., Tokyo, Japan) with a 306-channel whole-head system (Elekta Neuromag, Helsinki, Finland). The system had 102 sensor-triplets, each of which contained a magnetometer, a longitudinal gradiometer, and a latitudinal gradiometer. Silver cup electrodes were located at six sites of the body to measure individual ECGs and exclude noise from the ECG and EOG. The locations of three fiduciary points (nasion and left and right auricular points) defining the head frame coordinate system, a set of head surface points, and the locations of the four head position indicator coils were digitized using an Isotrak three-dimensional digitizer (Polhemus™, Colchester, VT, USA). MEG and EOG signals were simultaneously recorded during stimuli presentation at a sampling rate of 1,000 Hz. All off-line analyses were based on the saved continuous raw data. Sleepiness scores at the time of the MEG examination were assessed using the Stanford Sleepiness Scale (47 (link)) before and after each task.

Ten minutes of eyes-closed resting-state MEG was recorded in a magnetically shielded room using a 306-channel whole-head system (Elekta Neuromag Oy, Helsinki, Finland) at a sample frequency of 1250 Hz, an online anti-aliasing filter of 410 Hz, and high-pass filter of 0.1 Hz. Five head-position indicator coils and the outline of the participant’s scalp (± 500 points) were digitized using a 3D digitizer (Fastrak, Polhemus, Colchester, VT, USA) to determine the head position relative to the MEG sensors. MEG data was co-registered to the individual T1-weighted structural MRI scan. MEG recording was performed before or at least one week after MRI scanning to avoid potential magnetization artifacts. In April 2021, the system was replaced by a Triux Neo system (MEGIN Oy, Finland) with identical channel number and type, allowing combined use of data. Data for 3 mutation carriers and 4 healthy controls was acquired using the Triux Neo system at a sampling frequency of 1000 Hz, an online anti-aliasing filter of 330 Hz, and high-pass filter of 0.1 Hz. The scalp outline was obtained in a line-like manner (± 2500 points). Seven healthy control subjects were scanned on both systems for comparison (Supplementary Fig. 4). All subjects were in supine position during MEG recording and instructed to close their eyes, lie still, relax, and think of nothing in particular while staying alert.

In Amsterdam, MEG was performed using a 306 channel whole-head system (Elekta Neuromag Oy, Helsinki, Finland). Eyes-closed and eyes-open resting-state MEG data were recorded with subjects in supine position inside a magnetically shielded room. We will use transformed time series [101 (link)] to extract spectral properties (relative band power and peak frequency) [102 (link)], and estimates of functional connectivity between brain regions, and metrics that characterize the topology of the functional brain networks [103 (link), 104 (link)]. These analyses will be applied using Elekta’s beamformer software, and both in-house developed Matlab tools and BrainWave software (http://home.kpn.nl/stam7883/brainwave.html).