EEG Signal Quality of a Subcutaneous Recording System Compared to Standard Surface Electrodes

Figure 4

Similarity between surface and subcutaneous EEG recorded signal during “eyes closed” paradigm as calculated by (a) the normalized correlation coefficient and (b) the magnitude squared coherence spectrum. The maximum correlation at lag 0 for closed eyes is 0.73. The two side lobes are situated at lags −22 and 22, corresponding to a frequency of 9.4 Hz. Outside the shown lags, the correlation coefficient is close to zero. For the coherence spectrum, primarily the lower frequencies have higher coherence. The vertical dashed lines indicate the alpha-band.

(a)

(b)