In short, findings of theta decreases associated with good memory are limited to intracranial studies of memory success. Findings from non-invasive studies as well as from intracranial studies that specifically assess associative memory suggest that theta power increases underlie the encoding and retrieval of episodic memories in humans. Moreover, the relationship between theta and memory is bolstered by a rich theoretical and animal literature that link theta oscillations to memory and spatial navigation, even at the scale of cellular ensembles (see Box 2).
