Passive Avoidance Protocol

General Overview
This passive avoidance task is a one trial fear-motivated avoidance task in which the mouse learns to refrain from stepping through a door to an apparently safer but previously punished dark compartment. The latency to refrain from crossing into the punished compartment serves as an index of the ability to avoid, and allows memory to be assessed.

Apparatus
Training chamber consist of a rectangular chamber divided into 2 compartments. One compartment is lighted by an overhead stimulus light and the other is black so as to remain dark. The two compartments are separated by an automatic guillotine door and each has a grid floor placed through which a footshock can be delivered.

Procedure

Habituation
On habituation day mouse is placed in the lighted compartment, facing away from the dark compartment and allowed to explore for 30 seconds. After 30 seconds the door is raised and the mouse is allowed to explore freely. When the mouse enters the dark compartment with all four paws, the guillotine door is closed, and the latency to enter is recorded (from the time the door is lifted). Once the mouse crosses to the darkened chamber the door closed and the mouse is immediately removed and returned to the home cage.

Training
On training day mouse is placed in the lighted compartment, facing away from the dark compartment and allowed to explore for 30 seconds. After 30 seconds the guillotine door is lifted. When the mouse enters the dark compartment with all four paws, the guillotine door is closed, and the latency to enter is recorded (from the time the door is lifted). 3 seconds after the door is closed a footshock (0.5 mA, 2 seconds duration) is delivered. 30 seconds after the footshock the mouse is removed to it’s homecage.

Testing
On test day (24 hours after training), the mouse is returned to the lighted compartment, facing away from the dark compartment. After 5 seconds, the guillotine door is lifted. When the mouse enters the dark compartment with all four paws, the guillotine door is closed, and the latency to enter the dark compartment is recorded (from the time the door is lifted). The mouse is removed and returned to the homecage.