CLINICAL APPLICATION OF THE MEASUREMENT OF MAGNETIC FIELDS PRODUCED BY HUMAN BRAIN USING THE SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE

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The magnetic fields produced by electrical activities in the human brain are less weaker than those of earth. Therefore, in order to detect the brain's magnetic fields (magnetoencephalography, MEG), the superconducting quantum interference device(SQUID) is necessary. In this study, we succeeded to record the spontaneous and evoked MEG without the aid of magnetic shielding, and this is the first record in the clinical institution in Japan.First, we measured the environmental magnetic fields by a single channel dc-SQUID with a second order gradiometer (BTi, 601 Biomagnetneter) in whole day, and observed the noise spectrogram. Then, we chose midnight for recording, and the notchfilter was used to avoid the line frequency noise and its harmonics. Secondly, sleeping MEG and EEG were simultaneously recorded. Although in a previous neuromagnetic study, only few sleep spindles were recorded in MEG, we frequently observed them (especially near the central vertex). Moreover, sleep spindles were simultaneously seen in both MEG and EEG in some part of records, but in another part they were seen in either MEG or EEG only. These findings are probably due to the multiple origins of sleep spindles. Thirdly, the pattern reversal visual evoked EEG and MEG using light emitting diodes were studied. As results, a positived or negative peak in 100ms(F100) following stimulation was seen in magnetic fields, as same as a positive peak(P100) in EEG. And then, isomagnetic contour maps over occipital area for F100 component demonstrated its origin in medial areas of bilateral occipital lobes.