Fig. 2: Calcium activity in the rat RE encodes associative value during fear conditioning and extinction.

A Adeno-associated viruses (AAVs) encoding the GCaMP6f fluorescent calcium indicator were injected into the RE approximately three weeks before behavioral experimentation and recordings. GCaMP fluorescence was recorded with a chronically implanted fiber optic by interleaving blue (470 nm; GCaMP) and violet (410 nm; isosbestic) light. B Representative viral spread and fiber tip locations for all rats (n = 9). C Experimental timeline. D Percentage of freezing behavior levels during each of the recording days averaged for all animals (n = 9 for all days, except for Context Extinction Retrieval, which is n = 7). CS-evoked fluorescence averaged across trials and animals during habituation (n = 9) (E), conditioning (n = 7) (F), cued extinction (n = 9) (G), and extinction retrieval (n = 9) (H). I Heatmap showing averaged CS-evoked activity across animals for all five trials of conditioning. J CS− and K US-evoked activity across trials during conditioning (n = 7 each). L Heatmap showing averaged CS-evoked activity across animals for all 45 trials of extinction. Average peak evoked fluorescence at CS Onset (M) and CS Offset (N) during early extinction, late extinction, and extinction retrieval (n = 9 each, *p < 0.05, **p < 0.01). O Linear regression showing that average peak fluorescence at CS onset across early extinction, late extinction, and extinction retrieval positively correlates with freezing behavior. Data are represented as mean ± SEM. Schematic illustrations in C were created by the authors.