Define the term - magnetoencephalography
A variant ERP known as magnetoencephalography (MEG) has been developed. MEG, which is still in its infancy, requires upward of 60 electrodes to be attached to the participant's scalp, and takes advantage of the fact that when neurons are active they generate tiny magnetic fields. Event-related fields (ERFs) can be detected by an MEG analyser in much the same way as ERPs, but they provide a more accurate means of identifying the origin of particular signals. MEG can locate the source of maximum magnetic field activity in response to stimuli, and, if required, map these areas three dimensionally and in real time. This technique has been of use in identifying the precise focal origins of epileptic seizures, and, as I hinted as above, it has also been used to map areas of the somatosensory cortex.