MAGNETOENCEPHALOGRAPHY (MEG) Magnetoencephalography (MEG) is a non-invasive neurophysiological technique that measures the magnetic fields generated by neuronal activity of the brain. The spatial distributions of the magnetic fields are analyzed to localize the sources of the activity within the brain, and the locations of the sources are superimposed on anatomical images, such as MRI, to provide information about both the structure and function of the brain. MEG is also a direct measure of brain function, unlike functional measures such as fMRI, PET and SPECT that are secondary measures of brain function reflecting brain metabolism. MEG has a very high temporal resolution. Events with time scales on the order of milliseconds can be resolved, again differentiating MEG from fMRI, PET and SPECT, which have much longer time scales. This technique, has also excellent spatial resolution; sources can be localized with millimeter precision. It is completely non-invasive. It does not require the injection of isotopes or exposure to X-rays or magnetic fields. Children or infants can be studied and repeated tests are possible. MEG is complementary to other modalities, the information provided by each modality adds to the full picture.Magnetic fields are found whenever there is a current flow, whether in a wire or a neuronal element.The magnetic field passes unaffected through brain tissue and the skull, so it can be recorded outside the head. The magnetic field is extremely small, but can be detected by sophisticated sensors that are based on superconductivity .
Posted on: Sun, 03 Aug 2014 17:16:45 +0000
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