Figure 1.

Schematic flowchart of the experimental design. All rats were allowed to get familiarized with the home cage, experimenter, and recording conditions for several days, during which baseline EEG was recorded. On the day of the experiment, animals were either exposed to a complex labyrinth (EE) or kept in their home cages (controls) for the last 3 hr of the waking period, followed by an intervening period of 30 min back in the home cages. The animals were then placed in the recording box for monitoring of wake/sleep states until reaching criterion for WK, SW, or REM; the typical duration of this period was ∼80 min. Thirty minutes after criterion, animals were killed and their brains were processed for zif-268 expression by in situ hybridization.