We suggest that memory contrasts that specifically isolate associative mechanisms should reveal narrow-band low frequency oscillations, which are otherwise obscured by a spectral tilt (see Figure 3) or by a reduction in low-frequency power [35] that is related to less specific cognitive variables such as attention or task engagement. To the extent that the non-specific low-frequency power decrease is due to a tilt of the background spectrum, it can be characterized by specifically analyzing the shape of the power spectrum to separate the two phenomena. One such method is interchangeably referred to as BOSC (Better OSCillation detection) or Pepisode [58]. It searches for time periods during which there exists a narrow-band peak in the power spectrum that exceeds a certain amplitude relative to a fit of the background power spectrum for a certain duration (e.g. 3 cycles).
