How Does Prolonged Avoidance Training Affect OCD-Like Behaviors in Rats?

What you need to know

• Extended avoidance training in rats (20 days vs 8 days) leads to impaired extinction and persistent avoidance behaviors resembling OCD symptoms.
• Overtraining alters brain activity patterns associated with avoidance, shifting away from typical avoidance circuits.
• Extending the duration of extinction training can prevent the negative effects of overtraining on avoidance behaviors.

Avoidance training and OCD-like behaviors in rats

Obsessive-compulsive disorder (OCD) is characterized by repetitive, compulsive behaviors that often resemble avoidance of perceived danger. While these compulsions may temporarily relieve anxiety, they can become extremely disruptive to daily life. A common treatment for OCD is exposure and response prevention therapy, where patients are exposed to triggers but encouraged to refrain from compulsions.

To better understand how prolonged compulsive behaviors might affect the brain and treatment outcomes, researchers developed a rat model to study the effects of extended avoidance training. They trained rats to avoid a tone-signaled foot shock by moving to a safe platform, comparing groups trained for 8 days versus 20 days.

Extended training leads to persistent avoidance

Both groups of rats learned to successfully avoid shocks at similar rates. However, when researchers then tried to extinguish this avoidance behavior by presenting the tone without shocks, the overtrained (20-day) group showed severely impaired extinction compared to the 8-day group.

When later tested with access to the platform restored, 75% of overtrained rats showed persistent avoidance behavior compared to only 37% of rats with standard training. The overtrained rats also exhibited higher anxiety levels on other behavioral tests.

These findings suggest that extended repetition of avoidance behaviors, which may parallel prolonged compulsions in OCD, makes it much harder to extinguish those behaviors later. This could help explain why OCD symptoms often persist despite treatment.

Overtraining alters avoidance-related brain activity

To examine how overtraining affected brain activity, the researchers looked at patterns of c-Fos protein expression, which indicates recently active neurons. In rats with standard training, persistent avoidance was associated with increased activity in brain regions typically linked to avoidance behaviors, including the prelimbic cortex and nucleus accumbens.

Surprisingly, overtrained rats showing persistent avoidance did not exhibit this typical activation pattern. Instead, the minority of overtrained rats that successfully reduced avoidance showed increased activity in other regions, including parts of the insular and orbital cortex.

This suggests that extended training fundamentally alters how the brain processes and expresses avoidance behaviors. The typical avoidance circuits may become less active, potentially making the behavior more automatic and harder to consciously control.

Extending extinction training prevents negative effects

An important question is whether the negative effects of overtraining could be overcome. The researchers found that extending the extinction phase from 4 days to 10 days in overtrained rats reduced persistent avoidance back to normal levels.

This finding provides hope that even after prolonged compulsive behaviors, extended treatment may still be effective. For OCD patients, this supports the potential benefits of longer-duration or more intensive exposure therapy programs for severe, treatment-resistant cases.

Implications for understanding and treating OCD

This research in rats provides several insights that may be relevant for human OCD:

1. Prolonged compulsive behaviors may make it harder to extinguish those behaviors later, potentially explaining why long-standing OCD can be challenging to treat.

2. Extended compulsions may alter typical brain activity patterns, which could make the behaviors more automatic and less responsive to cognitive control.

3. Brain regions like the insular and orbital cortex may play important roles in successfully reducing compulsive behaviors after prolonged expression.

4. Extending the duration of exposure therapy may help overcome treatment resistance in severe OCD cases.

While the direct applicability of rodent studies to human disorders is always limited, this work provides a foundation for further research into the neural basis of persistent compulsive behaviors and potential treatment approaches. Future studies may investigate whether activating specific brain regions like the insula could enhance exposure therapy outcomes in OCD patients.

Conclusions

• Extended avoidance training in rats leads to extinction impairments and persistent avoidance resembling treatment-resistant OCD.
• Overtraining alters typical avoidance-related brain activity patterns, potentially making behaviors more automatic.
• Prolonging extinction training can overcome the negative effects of overtraining on avoidance behaviors.
• These findings may inform approaches to treating severe, long-standing OCD in humans, including extended-duration exposure therapy.