Figure 1.

Sketch of experimental procedures. A, The main experiment (Experiment 1, top row) started with a baseline measurement of electrophysiological activity for 3 h during the early light phase. Within the following acquisition phase in the Barnes maze, animals received 4 trials/d of training, starting at the beginning of the light phase. The target escape box (black circle) did not change its position relative to available extra-maze cues throughout the acquisition phase. Immediately after Barnes maze training, electrophysiological activity was recorded again for 3 h. Within this recording session, the OPTO received optogenetic inhibition during NREM sleep. For the 90 s probe trials at the beginning of the light phase on Day 5 and Day 16, the maze was rotated by 180° to prevent orientation on potentially present intra-maze cues while the extra-maze cues remained stationary. The escape box was removed and replaced by a blind (dark gray circle). In a control experiment (Experiment 2, Non-learning control), each animal was recorded on 2 d during the first 3 h of the light phase. Within one of the sessions, the optogenetic inhibition procedure was applied during NREM sleep, whereas the other session served as within-subject control. Black and white horizontal bars represent the dark and light cycle, respectively. B, Coordinates of AAV9-CaMKIIα-iChloC-2A-tdimer2 injection sites into vHC/iHC are schematized together with subsequent viral expression in projections of HC afferents to the mPFC, and the locations of the optic fiber implantations.