Figure 2. ‘Extinction neurons’ in the Ba, which appear after single-session extinction-training, disappear after multiple-session extinction-training.

(A) Experimental design. (B) CS-induced freezing throughout the entire behavioral training (n = 27 rats). (C) Two distinct neuronal subpopulations were identified. Fear neurons, n = 8 cells from 6 rats, red; extinction neurons, n = 6 cells from 6 rats, blue. (D) Averaged CS-evoked activities of fear and extinction neurons were plotted against freezing behavior. Friedman test revealed a significant change in neuronal and behavioral responses (Fear neurons, χ² = 14, p=0.0073, *p<0.05 for post-Cond versus the other groups, Friedman test followed by Dunn’s test; Extinction neurons, χ² = 10.67, p=0.0306, *p<0.05 for post-Ext1 vs. the other groups, Friedman test followed by Dunn’s test; Freezing behavior, χ² = 39.26, p<0.0001, p<0.01 for all designated pairs except Hab vs. post-Ext3, Friedman test followed by Dunn’s test). (E) Histological verification of the electrode placements.

DOI: http://dx.doi.org/10.7554/eLife.25224.005

Figure 2—figure supplement 1. Long-term single unit recordings in the Ba.

(A) Representative waveforms of a neuron recorded from a single electrode and observed throughout the behavioral training period. Grid, 55 μV x 100 μs. (B) Verification of long-term stable single unit recordings as previously described (Herry et al., 2008). (C) CS-evoked freezing of rats that fear (red, n = 6 rats) and/or extinction (blue, n = 6 rats) neurons were recorded from (upper) and averaged neural responses of fear (red, n = 8 cells) and extinction (blue, n = 6 cells) neurons in the Ba (bottom) throughout the training. The behavioral and the neural responses were averaged either for the first 5 CSs or the last 5 CSs.

DOI: http://dx.doi.org/10.7554/eLife.25224.006