eLife assessment
This study presents important findings that homo- and heterosynaptic plasticity outside of the window at which a weak associative fear memory is formed can transform this memory into a stronger one, and can produce fear memory even when stimuli were not paired. This work therefore expands our views on the role of time- and input-specificity of plasticity in learning processes. The evidence, based on state-of-the-art in vivo manipulations and activity recordings in behaving mice, supporting the conclusions is solid, although further validation of the methods used is required in order to reaffirm the authors' conclusion. Once resolved, the work will be of broad interest to neuroscientists interested in activity-dependent synaptic plasticity and associative memory.