While the electronics should now be replaced at the end of September, the warm-up artefact has lately sometimes taken over 1 h to appear after turning on the system, and 10-15 minutes to disappear after. Because of this, please keep the electronics on between scans during the day, and if there’s a scan early the next day, keep it on overnight. When I’m present, I’ll take care of logging the next person in and put the acquisition software back in “preview” mode. If I’m not present, try to come in an hour ahead if possible to log in and start the software.
Additionally, it seems that when the system is on for an extended period of time, the artefact may come back and linger in the high frequencies. We’ve seen it above 400 Hz. This is not too problematic in most cases, but turning off the electronics may get rid of it again. It’s not clear what’s the best approach, but I’d suggest that if the system has been on for many hours, to restart it, keeping it off between 10 s to 1 min, before you start your session and collect the empty-room recording.
Finally, the good news is that if the artefact appears during a recording, it can be cleaned pretty easily, e.g. with SSP, with 2 or 3 components. It’s easier to identify the components when it’s in the high frequencies, away from strong brain activity. The pattern seems stable even when the artefact sweeps across frequencies, but when that’s the case, a relatively narrow time window should be used to be able to focus on an appropriate frequency range with a strong artefact peak. See here for figures.