Development of Hybrid Small Sensor Module for Measuring Both Electroencephalogram and Cortical Hemoglobin Concentration

Abstract

The purpose of this study is to develop a small hybrid sensor module that is integrated an active electrode and an optical device, and to confirm the basic performances of the sensor module and the capability to measure brain activities. The active electrode is composed of an electrode plate and a preamplifier. The optical device is composed of a laser diode, photo-diodes, and preamplifiers. In order to confirm the basic performances, we measured the frequency response and the noise density of the electrode, the frequency response of the optical detector, the stability of the light source, and the response to hemoglobin concentration change. All of the basic performances were enough to measure brain activities. In order to confirm the capability to measure brain activity, an electroencephalogram (EEG) measurement experiment and a cortical hemoglobin concentration measurement experiment were carried out. EEG signals of alpha wave band were significantly weak during light stimuli (p < 0.05). Cortical hemoglobin concentration signals were significantly strong during Stroop test (p < 0.05). In conclusion, we developed the small hybrid sensor module and confirmed the basic performance and the capability to measure brain activities.