Fig. 2: Characterization of the in-ear electrophysiological sensing capability.
a–d, Electrode–ear impedance characterization with (a) impedance magnitude and (b) impedance phase over time upon insertion, and (c) impedance magnitude and (d) phase spectra in steady state after insertion for more than 2 min. e,f, EDO characterization with (e) temporal profile and (f) fitted normal distribution of the 96 EDO recordings. g,h, EEG characterization with (g) spectrogram and (h) power spectrum density (PSD) for alpha modulation experiments with participants opening and closing their eyes at 1-min intervals. The yellow-shaded interval denotes the 8–12 Hz alpha band in the EEG spectrum. i–l, Auditory steady state response (ASSR) PSDs for four acoustic stimuli amplitude modulated at (i) 25 Hz, (j) 40 Hz, (k) 55 Hz and (l) 70 Hz. m,n, EOG characterization. m, Transient response to various eye movements recorded within one ear with ipsilateral referencing. n, Comparison between contralateral and ipsilateral referencing in the time-averaged transient response to two representative eye movements: glancing up and blinking. Further EOG characterization can be found in Extended Data Fig. 5. The total number of measurements taken from each individual electrophysiological sensor per experiment is denoted as index n in each panel. For each electrophysiological sensor, solid lines and shaded bands represent participant-averaged mean ± s.d. of the measured time series and PSD.
