Fig. 1: Mean + SE startle magnitude during differential fear conditioning at baseline and follow-up.

There was a significant main effect of Visit, and a Block by Trial Type interaction for NA vs CS+, and CS+ vs CS−, indicating that fear potentiation to CS+ as well as discrimination between CS+ and CS− developed in blocks 2 and 3 of conditioning. NA noise alone, CS+ reinforced conditioned stimulus, CS− non-reinforced conditioned stimulus, HAB habituation.