Figure 1.

Mice re-exposed to the conditioned context for 24 min exhibited less freezing during testing than those re-exposed for 3 min. A) Mice were conditioned on Day 1, re-exposed to the conditioned context on Day 2 for 3 or 24 min, and tested on Day 3. Both groups showed comparable freezing during the acquisition and extinction sessions, but mice that were re-exposed for 3 min had significantly higher freezing during testing than those exposed for 24 min (p<0.05). B) The protocol from A was used with different conditioning chambers and a different tracking system (see Methods for details). Again, mice re-exposed to the conditioned context for 24 min showed less freezing than the mice re-exposed for 3 min (p<0.05). Percent freezing is shown during the acquisition, extinction, and testing periods in 3-min time blocks.