Analysis of EEG Frequency Components and an Examination of Electrodes Localization during Speech Imagery

This paper reports a result of analysis of EEG frequency components and an examination of electrodes localization for relating the intention ("I want to drink") to "with/without speech imagery" when drink images are displayed on the PC screen. An experimental process was set in 8 sec as followings; fixation image display (1 sec), drink image display (2.5 sec), intention check (1.5 sec), fixation image display (1 sec), and speech imagery period (2 sec). It was repeated 100 times. EEG was measured with 10-20 system in a magnetically-shielded room with BPF (0.08-100Hz) and notch-filter (50Hz) for 10 participants. In the analysis, it was averaged with 35 trials dividing between "with/without speech imagery" in an epoch (fixation image display and speech-imagery) of 2.9 sec. Event-related synchronization (ERS) and desynchronization (ERD) were examined with event-related spectral perturbation (ERSP) and t-test. ERS were observed in α band on the left-hemisphere in case of "with speech imagery" for latency of 500-1500 ms and the significant differences (p<; 0.05) were shown in the left-hemisphere and occipital-region. It is suggested the useful information of selecting electrode positions to detect EEG frequency components for judgment of "with/without speech imagery" in the intention. From these results, we examined the electrodes localization in the with/without speech imagery identification.