We then tested correlations in individual experiments for each pair at both 2–5 Hz and theta frequencies, shown in Fig. 4D. When calculated separately in each rat in this second analysis (Fig. 4D–F), significant correlations were found at 2–5 Hz in the majority experiments (87–93%; i.e. in 14 rats between PFC-nRE and in 13 rats for the other 2 pairs; Fig. 4D, blue). On the other hand, theta correlations between PFC and HC were only significant in 7 out of 15 (47%) rats, whereas theta was significant in 11 rats (73%) between HC and nRE and in 9 rats (60%) between nRE and PFC (Fig. 4D, red). Group averages indicated a similar structure of correlations (Fig. 4E–F), i.e. 2–5 Hz larger than theta, and the largest correlations for either 2–5 Hz or theta between nRE and the presumed origin of these oscillations.
