“Flash and freeze” synaptic plasticity

Neuroscience The eponymous mossy fibers in the hippocampus of the brain connect the dentate gyrus to the CA3 pyramidal region and are implicated in short-term memories spanning a few seconds to minutes. How such memories are held in the circuit is a puzzle. One candidate is post-tetanic potentiation, a form of synaptic plasticity that decays within tens to hundreds of seconds and regulates synaptic strength at hippocampal mossy fiber–CA3 pyramidal neuron synapses. Vandael et al. simultaneously recorded from pairs of mossy fiber terminals and postsynaptic CA3 pyramidal neurons and followed measurements with “flash and freeze” electron microscopy. The authors observed that post-tetanic potentiation was induced by an increase in the size of the readily releasable pool of synaptic vesicles in granule cells. Neuron 10.1016/j.neuron.2020.05.013 (2020).