| | DIRP Magnetoencephalography Core Facility
Magnetoencephalography (MEG) is a non-invasive procedure
similar to electroencephalography (EEG) in terms of basic
principles and analysis, however, MEG consists of sitting
in a chair or lying on a bed while your head is inside a helmet
shaped device which contains magnetic field sensors. These superconducting quantum interference device (SQUID)
sensors passively detect weak magnetic fields (10-14
Tesla) outside the head produced by brain activity. The 275 SQUID sensors are uniformly distributed, in
a grid, over the inner surface of the helmet that covers the
entire head. Head position within the magnetometer will
be determined before and after the MEG session by digitizing
the position of three indicator coils that are attached to
the pre-auricular and the nasion fiducial points. The
positions define the coordinate system for the signals.
Digital photographs of the fiducial points will also be taken
to localize the same points on the participant�s anatomical
MRI scan.
Magnetoencephalography can lead
to a better understanding of the functioning of the brain
because the potential to determine the spatial source of dipoles
is enhanced. With this technology signal detection is
practically unaffected by the conductivity and structure of
skull and scalp tissue. In addition, compared to EEG
systems, MEG systems allow higher spatial sampling resolution. Under favorable conditions, spatial localization of current
sources with whole head MEG is on the order of 2-3 mm at a
temporal resolution better than 1 ms.
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