Vetere, G. et al. Nat. Neurosci. 22, 933–940 (2019)

Memories are encoded in neural circuits and formed from experiences. Usually—new research suggests experience can be optional.

Mice will learn to associate an input, such as a smell, with an outcome—for example, a footshock. The next time they note that odor, they know to get out of the area. Artificially manipulating the synaptic pathways involved can then alter the resulting conditioned behavior. The researchers in the current study, attempting to reverse-engineer the memory formation process, found they could skip the whole experience element. Through optogenetic manipulation of olfactory neurons and those that mediate aversive behavior, they were able to impart ‘artificial’ memories in mice. These mice then responded to odor in the same way as odor-conditioned animals, despite never having actually smelled the aversive odor before.