3.8. Visually Guided Behavior: Light Cued Fear Conditioning

Prior to the experiment, inject control mice with sham injections (PBS) to control for the virus treatment.

The experiment is done over three consecutive days: habituation on day 1, training on day 2 and testing on day 3.

Start every day by spraying the Habitest chamber meticulously with ethanol to prevent odor from previous experiments to impact visually guided behavior.

On day 1, bring the animals into the testing room in their home cages and then acclimatize them individually to the Coulbourn shock chambers for 30 min.

On day 2, train the mice by subjecting them to paired or unpaired light cued fear conditioning. Training consists of 5 min habituation to the chamber followed by three shock trials at 0.7 mA. For paired trials synchronize the 20 s light cue (see Note 10) with 3× 2 s foot shocks at 4 s inter-shock-interval with 40 s inter trial interval. For unpaired trials, provide the same amount of foot shocks and light cues but in a random order without synchronization. These brief, low current shocks provide the minimal aversive stimulus to create a fearful memory associated with a light cue.

On day 3, test the animals in a fear probe trial. Change the floor of the chamber from the shock grid to a solid floor. Then allow the mice to habituate to the chamber for 5 min, and then present the same light stimulation protocol as on day 2, but without shock, while recording their movement and behavior with the Freeze-frame software.

Use the video recordings to analyze conditioned fear behavior (time spent freezing, a typical rodent fear response) associated with the learned light cue.