Data from: Reactivation of memory-associated neurons induces downstream suppression of competing neuronal populations

Inducing apparent memory recall by tagging and optogenetically
reactivating cells in the hippocampus was demonstrated over a decade ago.
However, the hippocampal dynamics resulting from this reactivation remain
largely unknown. While calcium imaging is commonly used as a measure of
neuronal activity, GCaMP, the most common calcium indicator, cannot be
used with optogenetic neuronal reactivation because both require blue
light excitation. To resolve this overlap, we demonstrate optogenetic
reactivation with a red-shifted opsin, ChrimsonR. We then conduct
dual-color calcium imaging in CA1 during memory reactivation in DG. In
addition to measuring population dynamics in CA1, CA1 cells tagged during
the original experience were identified. In the fear conditioned animals
(FC+), non-tagged cells in CA1 decreased their firing rate during
stimulation, while tagged cells maintained their activity level. In the
FC+ animals, as the behavioral effect of stimulation decreased across
days, so did the changes in neural activity during stimulation. Our
results both demonstrate the technical feasibility of calcium imaging
during optogenetic reactivation of memory-associated neurons and advance
our understanding of the dynamics underlying this reactivation.