It has also been called Rhythmic Slow Activity (RSA), to contrast it with
the Large Irregular Activity (LIA) that usually dominates the hippocampal EEG when theta is not present.
Green and Arduini described an inverse relationship between hippocampal and cortical
activity patterns, with hippocampal rhythmicity occurring alongside desynchronized
activity in the cortex, whereas an
irregular hippocampal
activity pattern was correlated with the appearance of
large slow waves in the cortical EEG.