Brain activity measurement in the occipital region of the head using a magneto-impedance sensor

We have achieved pico-Tesla (10
^-8
Oe) resolution for micro magneto-impedance (MI) sensors by utilizing the ultra-low intrinsic noise of amorphous wire the pulse magneto-impedance effect. We previously reported a study on bio-magnetic measurement using a pico-Tesla resolution MI sensor without any magnetic shielding. In order to detect very weak magnetic fields such as bio-magnetic fields, we constructed an MI gradiometer to cancel out background uniform noise such as the geomagnetic field. In the present study, we measured brainwaves using an MI sensor, and the results showed that brain activity can be evaluated by the sensor. We compared our results with electroencephalogram (EEG) and magneto-encephalogram (MEG) data reported by previous studies, and considered the reliability of the data. The results suggest that the MI sensor is a convenient device for daily monitoring using MEG signals.