In this review, we sought to reconcile conflicting findings on the presence of theta activity during memory processing. We noted that theta power decreases are commonly observed in intracranial recordings, often associated with an overall tilt of the power spectrum. And though we have discussed how this tilt effect can obscure true underlying increases in oscillations, the tilt remains a widespread phenomenon that could play an important role in brain function. Indeed, beyond studies of human memory, the tilt has also been observed during mathematical computation and sensory processing (see Box 2).
