MEG

Subject Preparation

Taking a subject in charge upon her/his arrival at Neurospin

Subjects arrive 45 minutes before the start time of the experimental session marked on the GRR and are usually taken in charge by LBIOM nurses (but see below). Subjects are informed on the experiment, debriefed to check any counter-indication to undergo the experiment, and asked to sign their consensus to take part in the experiment. They then wear a single-use pajama and nurses check that they don't have any magnetic object on them.

IMPORTANT: While most of the times the nurses will take care of the subject, the experimenter is expected to do it in situations in which nurses are too busy. Therefore the experimenter should be acquainted with the procedure (see this document) and should be around at least 45 minutes before the session so that she/he can be alerted by the nurses.

Subject preparation

Subject preparation is done in a consultation room next to the MEG room. Thus, the next subject can be prepared while the previous one is still being recorded.

MEG users are expected to be able to do the preparation themselves should the nurses be not available or just to speed up the process by helping them.

EOG & ECG electrodes placement

This step will be performed in the consultation room. Ask the subject to lie down on the examination bed. EOG and ECG electrodes have to be placed on the participant as follows:

VERTICAL EOG Black & Blue electrodes labeled VEOG: one above the left eye, one below the left eye

HORIZONTAL EOG Green & Red electrodes labeled HEOG: one on the left temple, one on the right temple

ECG: Red & Green electrodes labeled ECG: one below the left clavicle, one on the right abdomen

GROUND: Black electrode labeled GROUND to be placed on the bone of the clavicle

Cleanse the skin with the abrasive Nuprep gel. Gently wipe the skin with an alcohol pad. Put a double-face-tape on the electrode. Fill the electrode with conductive paste EC2. Affix the electrode onto the skin.

For the ECG and GROUND electrodes in particular, maintain them into place with additional micropore tape.

Installation of the EEG cap and digitazion

Not systematically but in some cases, you will record EEG simultaneously to MEG. In this case, you have to also install EEG cap:

- Tell your subject what you are going to do (installation of the cap) and ask authorization to manipulate his head
- measure the dimension of the subject's head and choose which cap to use ( 46-52 cm, 52-58 cm or 58-62 cm)
- clean the scalp of the subject with alcohol if the subject has something in his/her hair
- put the cap on the subject's head
- check the position of the cap by measuring the position of the Cz electrode with a soft meter: it must be at the middle between LPA and RPA and Nasion and Inion
- check the impedence of your electrodes Impedencemeter

At this point, you have to digitize the head position (see HPI placement and Digitization sections)

After digitization, apply conductive gel in each electrode as follow:

- inject gel in each electrode after gently removing the hair and rubbing the skin with the syringe. Be careful not to make bridges between electrodes by injecting too much gel.
- soak the syringe in a bassin