Running an experiment (SOP2)

To record EEG data, first switch on the recording computer. In B114 the newer system boots straight to the desktop; on the older system you should log on to the ‘pat’ account, which has no password. In B004 the computer is networked, so you should log on with your Psychology (not central university) credentials. In C220 you log into the desktop PC using the username and password that are taped to the base of the monitor. 

From the desktop, launch the ASA program. It will sometimes ask you to open a study, at which point choose ‘Cancel’. Then click on the ‘Setup Recording’ button on the top toolbar. This will open a dialog box allowing you to enter participant details, and select a montage.

The montage contains all of the information about your EEG setup such as the number and names/locations of channels, the type of reference used, and the recording of any auxiliary electrodes such as EOGs.  For most experiments either the WaveGuard64 or WaveGuard32 montages are sufficient. If the 32 channel montage is selected, only the electrodes with white surrounds (on the outside of the cap) will be recorded – the green ones will be ignored and do not need to be filled with gel. See the ASA manual for more information on setting up a custom montage.

On dismissing this dialog box, you should see a continuous output from the EEG amplifier, with traces for each channel in the montage. If you have already connected the blink electrode, this should be giving a signal. Click the ‘check impedances’ box to show a schematic of the cap with impedance values for each electrode in your montage. Follow the instructions for setting up the cap, and exit this screen when the impedances are acceptable. You should now see a separate trace for each electrode, and are ready to being recording.

Ensure that your triggers are working (see the page on Synchronising with the EEG system). Prepare your stimulus computer and ensure that your participant is ready and aware of what you expect them to do during the experiment. Remind them that they should keep still, and minimise blinks. When you click the ‘start recording’ button, ASA will begin saving the data to disk. At the end of the session, click ‘stop recording’. The data are saved automatically to the default output directory, and will have a time and date stamp as the filename. If you close the recording window after each block of your experiment, and set up a new recording session, then each block will be saved to a separate file. If you start and stop multiple times within the same file, then each block will be saved in one large file (this can cause problems for some analysis software).