General information about MEG experiments

The human Magnetoencephalogram (MEG) records the small changes in magnetic fields at the surface of the head generated by nerve cell activity inside the brain. In the MRC COGNITION AND BRAIN SCIENCES UNIT, we are now using this technique for measuring brain activity related to human perception and cognition. 

The experiments address questions about the brain basis of memory and perception. We will be happy to explain to you, in case you are interested, the ideas and hypotheses that motivate the experiments. However, such explanation has to wait until after the experiment, as knowledge about the hypotheses of an experiment may influence the participants’ behaviour and strategies. You can withdraw from the experiment whenever you like without giving a particular reason. The following paragraphs are designed to inform you about some general aspects of the methodology.

You are not exposed to external electrical or magnetic fields. The top of your head will simply be positioned within a helmet-like device that can measure the very weak magnetic fields produced as a normal consequence of activity in your brain. Possibly, a handful of sensors will also be attached to your forehead with tape (which should not cause discomfort nor leave any mark), just to measure the precise position of your head relative to the helmet. During the experiment, you will see words or pictures of objects or faces projected onto a screen in front of you, and may be asked to press buttons according to a simple task. The experimental procedures will be explained in more detail and you will be given the opportunity to practice and ask questions.

The experimental session typically takes about 1 hour. Preparation time for a simple experiment is usually about 15 minutes. However, this can vary depending on the type of experiment, and you will be informed about the specific details before the experiment. 

Because the magnetic signals we measure are very weak, we would like to avoid any possible source of recording artefacts. In particular, it is important that muscle activity, eye movements and eye blinks are minimised (though, of course, not completely suppressed). We will therefore ask you to sit or lie as still as possible during the experiment.  

We assure you that the data we acquire will be kept confidential. Details of the data storage will be clarified on a different form.

You will be paid for your participation. Payment will be for the entire time spent in the lab (including preparation etc.). The current rate is £ 10 per hour.

	Again, we emphasise that questions about the background of the experiment or the procedures are always welcome. In addition, we would appreciate your feedback about your impression of the experiment.