Learning Objective
Explain behavioral models of depression, including learned helplessness and low response-contingent reinforcement, and understand their physiological and clinical correlates.
Learned Helplessness (Animal Model of Depression)
Definition:
After repeated uncontrollable negative events, normal avoidance responses are extinguished.
Animal Example:
- A rat is repeatedly shocked without the opportunity to escape.
- Eventually, even when escape is possible, the rat does not avoid the shock.
Physiologic Features:
- Passivity
- Norepinephrine depletion
- Difficulty learning new responses that produce relief
- Weight/appetite loss
Human Example:
- A woman in an abusive relationship perceives she cannot escape, leading to depression.
Neurobiology:
- Increased GABA in the hippocampus reduces the likelihood of learned helplessness.
Activity
Low Response-Contingent Reinforcement
Definition:
- Depression may result from too little predictable positive reinforcement, creating prolonged extinction-like effects.
Mechanism:
- The person lacks social skills to elicit positive reinforcement.
- Passivity and low motivation develop.
Human Examples:
- A man who receives no appreciation from his spouse may become depressed.
- A caring father who feels unappreciated by family may experience depressive symptoms.
Key Concept:
- Depression can be understood as behavioral passivity due to extinction or lack of reinforcement.
