Infralimbic cortex controls fear memory generalization and susceptibility to extinction during consolidation

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Memory Consolidation

Background:

• Inactivation of the infralimbic (IL) subregion of the medial prefrontal cortex before fear memory acquisition leads to generalized and extinction-resistant fear memories.
• The role of the IL during the consolidation phase in modulating memory specificity and extinction susceptibility remains unclear.

Purpose of the Study:

• To investigate the role of the IL in controlling memory generalization and extinction susceptibility during fear memory consolidation.
• To determine the temporal dynamics of IL involvement immediately after acquisition versus later during consolidation.

Main Methods:

• Temporary inactivation of the rat IL using muscimol immediately after contextual fear conditioning.
• Inhibition of protein synthesis in the IL using anisomycin during memory consolidation.
• Assessment of memory generalization, extinction, and extinction recall.
• Evaluation of anxiety levels using the elevated plus-maze test.

Main Results:

• IL activity immediately, but not 6 hours, after acquisition controlled memory generalization for over a week.
• IL inactivation during consolidation impaired extinction memory recall the next day, without affecting within-session extinction or anxiety levels.
• Anisomycin administration indicated that IL protein synthesis during consolidation primarily supports extinction-sensitive fear memories over memory specificity.

Conclusions:

• The infralimbic cortex plays a critical role in regulating fear memory generalization and extinction susceptibility during the consolidation period.
• Immediate post-acquisition IL activity is essential for controlling memory generalization, while IL protein synthesis during consolidation is vital for extinction memory formation.