Mice normally freeze in position as a response to fear, as shown here under control condition (center row): fear conditioning induces freezing behavior in response (recall) to exposure to the conditioned stimulus (tone), but the freezing response normally decreases (extinction) following several days of multiple tone exposures (the mice get used to it). However, enhancing release of acetylcholine (blue light) to the amygdala during conditioned fear training resulted in continued freezing behavior 24 hours later and persisted over long periods of time (extinction).