Traditional EEG devices involve attaching electrodes to the scalp, in close proximity to the brain, for measurement. However, for those of us aspiring to enhance well-being through the power of neuroscience, the conventional measurement methods lack the convenience that everyone can easily practice, making them less desirable.
Therefore, we have developed earphone-type EEG devices that read brainwaves through the external ear canal, attempting to obtain data with the same level of accuracy as traditional EEG devices.
For our preliminary experiment, we initially confirmed the similarity of signals between a commonly used conventional EEG device (Brain Amp DC), typically employed in medical applications, and the earphone-type EEG device.
As a result, we found a high correlation between the brainwaves obtained through the ear canal using the earphone-type EEG device and those acquired through the conventional scalp-based method (T7/T8), following the traditional measurement approach (Figure 1).
Furthermore, from this data, to confirm the similarity of the brainwave components specifically acquired from the ear canal, considering the unique design of the earphone-type EEG with the reference electrode attached to the neck, we conducted a comparison by applying Average reference processing to T7/T8 and the left and right ear canal electrodes. As a result, even when completely eliminating the influence of signals such as electrocardiograms obtained from the electrode attached to the neck, the earphone-type EEG still showed a high correlation with the data obtained from the conventional EEG (Figure 2). Moreover, the significant correlation in the alpha wave band suggests that brainwaves acquired from the ear canal primarily consist of alpha wave components.
Based on the results of this preliminary experiment, the main experiment involved obtaining brainwave data during both resting state and the execution of working memory tasks in 11 healthy males in their 20s (excluding 2 individuals due to equipment malfunctions). The acquired data underwent Average reference processing, and correlations were calculated for the time evolution of the power components (signal components) between electrodes during the six sessions of working memory tasks.
As a result, the signals from the earphone-type EEG device showed a relatively high correlation with the electrodes on the scalp (Figure 3). This suggests that, even from the ear canal electrodes, although not a perfect match with the scalp-based EEG signals, the recorded data exhibited a certain degree of similarity.
Furthermore, after applying Bonferroni correction, we calculated the survival rate of statistically significant electrode pairs. In the alpha wave band at 10Hz, a significant correlation between the ear canal and scalp-based EEG was observed in approximately 20% of the data (Figure 4).
From the above results, it has become evident that using the earphone-type EEG device, rather than the conventional method of measuring brainwaves from the scalp, could provide a more convenient means of measuring brain activity. Such findings may contribute significantly to the future integration of brainwave measurement into our daily lives, as we seek means to pursue happiness, ultimately enhancing the quality of our lives.
Research Presentation Information:
Inoue D, Ueda K, Ibaraki T, Imamura Y. Development of a neurofeedback system using In-Ear EEG for eustress-distress modulation. Poster presented at: Neuroscience 2022; Nov 16, 2022; San Diego, CA.