Prefrontal cortex neuronal ensembles encoding fear drive fear expression during long-term memory retrieval.

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Memory Research

Background:

• The prefrontal cortex, particularly the prelimbic (PL) region, is crucial for regulating fear expression.
• Neuronal ensembles are thought to encode memories, with their reactivation necessary for recall and behavior.

Purpose of the Study:

• To investigate if PL cortex neuronal ensembles active during fear memory encoding contribute to long-term fear expression during retrieval.
• To determine the role of these specific ensembles in conditioned behaviors.

Main Methods:

• Utilized viral-mediated TRAP (Targeted Recombination in Active Population) technology to identify and target PL cortex ensembles active during fear conditioning.
• Expressed inhibitory Gi-DREADD in these fear-encoding ensembles.
• Trained rats in lever pressing for food, subjected them to Pavlovian fear conditioning, and tested memory retrieval 28 days later.

Main Results:

• Chemogenetic inhibition of fear-encoding PL cortex ensembles significantly reduced conditioned suppression of food seeking in female rats.
• This inhibition did not affect conditioned suppression in male rats.
• Neither context nor tone freezing behavior was altered by the manipulation during the retrieval test.

Conclusions:

• Fear-encoding ensembles within the PL cortex play a role in long-term fear expression.
• This role is dependent on the sex of the animal and the specific modality of fear expression (e.g., instrumental vs. freezing).