Before scanning, it is essential that the participant is fully relaxed in the MEG scanner. This is particularly important if it is the participant’s first scan. There are two sources of potential problems that can occur from ill at ease participants. Firstly, an uncomfortable participant will wriggle about to make him or herself more comfy, which will generate muscle artefacts amongst other things. Secondly, if the participant is anxious, responses to your sensory or cognitive paradigm will be masked, or at the least attenuated by their discomfort (be it by reduced attention or by cortical responses to anxiety). Also, it is vital to ensure that there are no artefacts generated by the participant wearing any metal objects. The following procedures ought to minimise the above concerns.
Before putting a participant in the scanner, familiarise them with the scan room and the scanner. Explain that MEG records responses passively, so the only direction of activity is from the brain to the recording equipment. The reason for the shielded room is to minimise interference from outside objects, not to stop magnetic fields from the scanner escaping. An example you may like to use is that the size of the magnetic fields we record from the brain are equivalent to the fields that would be generated by a car being driven 1 mile away. Hence it is vital to reduce any external interference. At all times whilst they are in the scanner, they can be heard via the intercom and observed via the camera. And at any point during the scan, if they are uncomfortable with the procedure they are able to request that it is aborted.
It is essential to establish intercom contact as soon as you have shut the shielded room door after digitization. This is principally to put the participant at ease; however, it is also necessary to establish that the intercom is working properly. So, say hello, ask them if they are comfortable, then tell them that you are going to spend a couple of minutes setting up the acquisition parameters, and that you will speak to them again before the recording begins. Un-explained silences typically make participants nervous, and if they are nervous already, it’s just going to make things worse.
Once you have finalised your acquisition parameters, check that you can see responses from the participant and that there are no artefacts. After performing these checks, assuming that they are normal tell the participant that everything looks great, and that you will start the scan. (If everything is not normal you will have to ask them to remove the offending metal items.) Just before starting scanning, check the participant is still comfortable and happy to proceed. If they are, tell them to sit still and that you will speak to them in x minutes at the end of the run.
When the run finishes. Speak to your participant again. Tell them that everything went well, and to relax – but stay seated / supine until the next run / someone comes in to get them out of the scanner. Again, if there is going to be another set up period before another run, tell them you will speak to them in 2 minutes or whatever. If you are going to take a while setting up, you may want to open up the scan room door to give them some air.
As a general rule, when speaking to the participant, try to sound relaxed and in control. The impression you give will often dictate how they feel during the scan. If you’re worried, then they will be worried. However, if you are relaxed and happy, there is a good chance that they will be too.