Extended Data Fig. 7. Chemogenetic manipulation of the neuronal ensemble overlap is sufficient to link two distinct contextual memories.
(a) All mice received a bilateral injection of lentivirus DREADD hM3Dq-T2A-EGFP which infects a sparse population of RSC neurons. Representative images demonstrating hM3Dq-T2A-EGFP infection of RSC neurons from two mice on the left. Scale: 100 and 20 µm. (b) All mice explored two different contexts 2 days apart and were subsequently shocked in one of these contexts. Neuronal excitability was increased in a small subset of RSC neurons by administering a CNO (0.5 mg/kg) injection 45 mins before each context exploration. The control mice only received the CNO injection before the second context exploration. (c) Control mice display low levels of freezing in a novel as well as the previously explored neutral (Context A) context but freeze more in the training context (Context B). In contrast, mice from the experimental group display memory linking: Both the previously explored contexts (Context A and B) elicit high freezing relative to the freezing in a novel context. (TWRM ANOVA, Ftime (1.8, 44.9) = 28.45, p < 0.0001; Dunnett’s multiple comparisons test; Saline-CNO, n = 15, CNO-CNO, n = 12,). The physical contexts presented were counterbalanced to minimize any effect of context similarity. Data represent mean ± s.e.m. and each data point, * p < 0.05, ** p < 0.01, *** p < 0.001.