Hippocampus, aging, and segregating memories.

Rats use time-of-day cues to modulate learned taste aversion memories. If adult rats are accustomed to drinking saline in the evening and they receive a lithium chloride injection after drinking saline in the morning, they form a stronger aversion to saline than rats that were conditioned after drinking saline at the familiar time. The difference indicated that the rats formed segregated representations of saline taste and the time of day the saline was consumed.