Mapping the Imagined Speech Location on the Brain Scalp Through Magnetoencephalography (MEG)

Abstract

People with autism speech disorders, paralysis, or muteness cannot communicate via speech. These individuals can think but cannot express and create overt speech. As a result, the system must obtain and interpret the electric and magnetic signal developed at the Scalp during imagined or intended speech. These magnetic signals are termed MEG (Magnetoencephalography), and electrical signals are named EEG (Electroencephalography). This technology must be wearable, non-invasive, and easy to use daily. To make the system wearable, the location of the electrode is essential. Since the EEG has good temporal resolution but poor spatial resolution, mapping the area on the Scalp of imagined speech is difficult. Similarly, the MEG has an excellent spatial resolution. But the MEG signal is weak, only up to 10-9 T to detect. Therefore, the delicate magnetic field in the brain due to imagined speech can be seen only by an OPM (Optically Pumped Magnetometer) or SQUID sensor. This paper explores a slightly different type of sensor based on an optically pumped magnetometer with a low cost as the cost of SQUID and OPM is large. A self-made magnetic sensor is used to map the location on the Scalp. The MEG and EEG measurement has been done in terms of PSD (Power Spectral Density). An analysis calculates the deviation compared with a different located point on the Scalp. The area on the Scalp of imagined speech was selected with the help of a literature review. The EEG measurement has done to confirm the location.