Figure 2.

Histology and fear expression during recording sessions. a, Example of histological verification of recording site in the NAc core (b) and within the NAc shell. c, Diagrammatic representation of electrode placements for all animals within the NAc. Core-conditioned placements are indicated in orange (n = 5), Shell-Conditioned placements are indicated in cyan (n = 6), and placements for control animals are shown in black (n = 11). Although the placements are distributed throughout both cerebral hemispheres here for clarity, recordings from all animals were taken from the same hemisphere. Red indicates the examples shown in a and b. d, Percentage freezing during fear expression for core-conditioned, shell-conditioned, and control animals. There was no difference between conditioned groups in fear expression. Unconditioned rats did not freeze during CS presentation. All conditioned rats showed robust freezing that attenuated as the session progressed. By the end of the session, conditioned rats showed no more freezing than control rats.