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Respiration & Neural Dynamics in Odor Fear Learning

Timing is an essential aspect of learning and behavior, both in humans and animals. Understanding how organisms perceive and encode time intervals is crucial for comprehending various cognitive processes. In the context of associative learning, temporal relations between events play a significant role, and recent studies have shown that animals can rapidly acquire temporal information. However, the emergence of this temporal learning and the underlying mechanisms require further investigation. This blog post explores a study that aimed to investigate time encoding in odor fear conditioning and the involvement of dopamine (DA) in the amygdala’s role in processing the interval between conditioned and unconditioned stimuli.

Time Encoding in Odor Fear Conditioning

This study1 from Dupin et al utilized a combination of behavioral and physiological indices to monitor the fear responses of rats during odor fear conditioning. Three complementary indices were analyzed: freezing behavior, respiratory activity, and ultrasonic vocalization (USV) production. By observing these responses, the researchers aimed to identify if temporal patterns emerged based on the duration between the conditioned stimulus (CS, an initially neutral odor) and the unconditioned stimulus (US, footshock).

Methods

The study used emka & SCIREQ plethysmography in a sound-attenuating cage. The apparatus measured respiratory parameters, delivered air and odorants through three Tygon tubing, and allowed recording behavioral responses such as freezing behavior and ultrasonic vocalizations. Previous studies2 from this laboratory used the emka rodentPACK in conjunction with plethysmography to measure the temporal course of both the respiration and the local field potentials during odor-shock intervals.

Key Findings

The findings of the study were twofold. Firstly, by analyzing the behavioral and physiological indices, the researchers inferred that interval timing could be detected in the animals’ behavior after a few training trials. Specifically, they observed a decrease in freezing behavior, a decrease in respiratory rate, and an increase in USV emission just prior to the arrival of the footshock. Secondly, the study demonstrated that D1 receptor dopamine transmission in the amygdala played a role in timing the CS-US interval. By blocking dopamine D1 receptors, the researchers observed an alteration in timing behavior during both the acquisition and retention sessions.

Retained Memory of Interval Duration

The animals’ retention of the learning was tested 24 hours later, revealing timed anticipatory responses characterized by an increase in freezing behavior and a decrease in respiratory rate around the expected time of shock arrival. This suggests that the animals had stored the duration in their long-term memory.

Conclusion

The present study contributes to our understanding of time perception and the neural mechanisms involved in interval timing. By investigating odor fear conditioning in rats, the researchers revealed the emergence of temporal patterns in behavioral and physiological responses. Additionally, they demonstrated the involvement of dopamine D1 receptor transmission in the amygdala in timing the CS-US interval. These findings have implications for further research on timing mechanisms and shed light on the complex interplay between different brain regions involved in temporal processing.

References

1. Respiration and brain neural dynamics associated with interval timing during odor fear learning in rats. Dupin et al. (2020) Scientific Reports.

2. It’s time to fear! Interval timing in odor fear conditioning in rats. Shionoya et al. (2013) Frontiers in Behavioral Neuroscience

 

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