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Updated: Jun 12, 2025
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Contextual and Cued Fear Conditioning Test Using a Video Analyzing System in Mice
Published on: March 1, 2014
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Sex differences in contextual fear expression are associated with altered medial prefrontal cortex activity
Katherine Vazquez1, Ryan G Parsons1
1Stony Brook University, Department of Psychology, 100 Nicolls Rd., Stony Brook, NY, 11794.
Biorxiv : the Preprint Server for Biology
|September 24, 2024
Summary
Sex differences exist in contextual fear expression. Males show more freezing behavior, while neural activity in the prelimbic and infralimbic cortex differs between sexes, impacting posttraumatic stress disorder research.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Comparative Psychology
Background:
- Understanding the neural basis of fear expression is crucial for studying pathological fear responses like posttraumatic stress disorder (PTSD).
- PTSD is more prevalent in females, yet neural circuit interactions in female rodents during fear expression remain understudied.
- Investigating sex differences in fear circuitry can provide insights into PTSD pathophysiology.
Purpose of the Study:
- To determine if neural activity differs between male and female rats in specific medial prefrontal cortex (mPFC) projections during contextual fear expression.
- To examine neural activity in mPFC neurons not projecting to the ventrolateral periaqueductal gray (vlPAG) between sexes.
- To elucidate the role of sex in fear circuitry activation.
Main Methods:
- Infused a viral retrograde tracer into the vlPAG of male and female rats.
- Trained rats in a contextual fear conditioning task, followed by re-exposure to the context.
- Measured neural activity using EGR1 immunofluorescence in specific mPFC regions (vlPAG-projecting and non-projecting neurons).
Main Results:
- Males exhibited significantly higher freezing behavior than females during the contextual fear test.
- In vlPAG-projecting neurons, males showed increased EGR1 expression post-training and testing compared to controls; females did not show significant changes.
- In non-vlPAG-projecting neurons, males had higher fear-induced EGR1 in the prelimbic cortex, while females showed higher EGR1 in the infralimbic cortex.
Conclusions:
- Sex differences in contextual fear expression are associated with distinct neural activity patterns in the medial prefrontal cortex.
- The prelimbic and infralimbic cortex exhibit differential activation between sexes, suggesting their involvement in sex-specific fear responses.
- These findings contribute to understanding the neural underpinnings of sex differences in fear and PTSD.
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