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Measurement of Somatosensory Evoked Magnetic Fields Using Adjustable Magnetoresistive Sensor Array
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  • Tetsuro Tatsuoka ,
  • Shigenori Kawabata ,
  • Jun Hashimoto ,
  • Yuko Hoshino ,
  • Tomohiko Shibuya ,
  • Yoshiaki Adachi ,
  • Atsushi Okawa
Tetsuro Tatsuoka
TDK Corporation (currently METOOL Inc.), METOOL Inc.

Corresponding Author:[email protected]

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Shigenori Kawabata
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Jun Hashimoto
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Yuko Hoshino
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Tomohiko Shibuya
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Yoshiaki Adachi
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Atsushi Okawa
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Abstract

An adjustable helmet-style magnetoresistive (MR) sensor array, a room-temperature magnetic flux sensor, was developed to demonstrate simultaneous multipoint measurement of the somatosensory evoked magnetic field (SEF). The SEF was measured in three healthy subjects using an array of 30-channel MR sensors placed on the left hemisphere of the head with median nerve stimulation in the right wrist and averaged over 8,000 measurements. An M20 component (maximum amplitude of 725 ± 257 fT, peak latency of 20.5 ± 0.45 ms), considered to originate from the primary somatosensory cortex, was observed at an approximate latency of 20 ms of the magnetic field waveform in all cases. The phase inversion observed around C3 corresponded to the palmar area of the primary somatosensory cortex on the contour map of the magnetic field at the M20 peak. The MR sensor, a relatively inexpensive and easy-to-use magnetic sensor that does not require a zero-field environment, was successfully used for simultaneous multipoint SEF measurements in humans and may be a promising option to realize a reasonable magnetoencephalography application device.