INVESTIGATION OF HUMAN BRAIN FUNCTION USING MICRO-SQUID.

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We developed a new multi (twelve) - channel gradiometer system with the smallest and highest quality superconducting quantum interference device (micro-SQUID). A very small distance (3.80 mm) between the sensor coils and the skin provides quite high spatial resolution. Since this was the newly-developed machine, at first, we had to solve many small problems in terms of hardware, software, and magnetic shielded room. Finally, it took approximately 2 and a half years to solve all problems. Then we started the experiments from 1999.The first study was published in Neurosciecne Letters in 1999 concerniong peripheral nerve function. The actual whole image of the sensory nerve action fields (NAF) of the human median nerve at the wrist were successfully recorded following digital nerve stimulation by using the micro-SQUID.The NAF showed the biphasic waveform at each of the 12 channels, and the isomagnetic field map clearly showed the moving quadrupole pattern. The quadrupole comprised a dipole for depolarization followed by another dipole with the opposite direction for repolarization. The polarized length of the nerve obtained by reconstructing the magnetic field maps was approximately 17 cm, and the magnetic field complex moved along the nerve from the distal to the proximal part of the wrist at 58.7 m/s.