The contextual fear conditioning protocol was adapted from V. C. Gomes and Landeira-Fernandez (2008) and involved acquisition and test trials. During acquisition, each animal was placed in the observation chamber for 4 min. At the end of this period, three unsignaled electrical footshocks (0.6 mA) were delivered, with each shock lasting 1 s and an intershock interval of 20 s. The animal was returned to its home cage 2 min after the last shock. The test trial occurred approximately 24 h after training. This test consisted of placing the animal in the same chamber as the acquisition trial for 8 min with no footshock or other stimulation during this period. Freezing behavior was recorded only in the test trial.