Discrimination of what, when, and where: Implications for episodic-like memory in rats

We investigated the discrimination of what, when, and where in rats (n = 5) using an eight-arm radial maze. Rats received daily training consisting of forced-choice visits to four baited arms, one of which was randomly chosen each day to contain chocolate (Phase 1). In Phase 2, all eight arms were available. After a short (30 min) retention interval (RI), the four arms that were not available in Phase 1 provided food. After a long (4 h) RI, the four remaining arms plus the arm containing chocolate provided food (i.e., the chocolate arm replenished). The rats visited the chocolate location after the long RI more than after the short RI. Next, chocolate was paired with lithium chloride, and subsequent testing used the long RI. The rats visited the chocolate location less after the taste-aversion manipulation than in previous training, demonstrating knowledge of what, when, and where. Implications for episodic-like memory are discussed.