Abstract
Multiple spaced trials of aversive differential conditioning can produce two independent longterm memories (LTMs) of opposite valence. One is an aversive memory for avoiding the conditioned stimulus (CS+), and the other is a safety memory for approaching the non-conditioned stimulus (CS−). Here, we show that a single trial of aversive differential conditioning yields one merged LTM (mLTM) for avoiding both CS+ and CS−. Such mLTM can be detected after sequential exposures to the shock-paired CS+ and unpaired CS−, and be retrieved by either CS+ or CS−. The formation of mLTM relies on triggering aversive-reinforcing dopaminergic neurons and subsequent new protein synthesis. Expressing mLTM involves αβ Kenyon cells and corresponding approach-directing mushroom body output neurons (MBONs), in which similar-amplitude long-term depression of responses to CS+ and CS− seems to signal the mLTM. Our results suggest that animals can develop distinct strategies for occasional and repeated threatening experiences.
Competing Interest Statement
The authors have declared no competing interest.
