Studies using this method have shown that hippocampal theta oscillations during episodic memory encoding predominantly occur at the edges of the conventional 4–8 Hz theta band (i.e. “slow” 2.5– 5 Hz and “fast” 5.5–10 Hz theta) [41]. When counting the number of electrodes that exhibited a significant SME using (conventional) spectral power, negative effects outnumbered positive effects, but positive effects were observed in the same low theta range in which the authors also found oscillatory activity, as measured with BOSC. While this study did not directly compare the prevalence of theta oscillations during successful versus unsuccessful encoding, another (scalp EEG) study did and found that theta (4–8 Hz) oscillations were associated with successful encoding of word pairs in cued recall (i.e. a memory success contrast) [59]. If this finding can be confirmed with intracranial EEG, it would suggest that oscillation detection algorithms offer a complementary way to uncover the presence of rhythmic theta activity during successful memory operations, even in the presence of a broad-band tilt of the power spectrum. More recent methods, such as IRASA (irregular-resampling auto-spectral analysis) [60],
