You can train a mouse to stress out on cue by having it associate a particular sound with an unpleasant experience, like a mild electric shock. A group of researchers at Columbia University did the opposite. They taught mice "learned safety" by having training them to associate a sound with the LACK of an electric shock.
Then they put the mice in the water and let them swim around. After a couple of minutes, mice usually stop moving around, apparently in despair, having lost the will to live. At least that's how scientists interpret that behavior.
As reported here (Here's the paper), mice trained in "learned safety" can regain their will to live when they hear their "happy sound" and they start swimming again. Apparently, mice can be trained to overcome depression.
And their brains showed some of the same biological changes seen in mice given antidepressant drugs.
Does this mouse have a happy place?