Ventral Hippocampus Modulates Prefrontal Control of Background Contextual Fear After Cued Extinction

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Psychology

Background:

• Fear extinction is vital for treating anxiety disorders.
• The ventral hippocampus (vHPC) to prelimbic cortex (PL) pathway is known to regulate cue-specific fear after extinction.
• The role of this pathway in contextual fear memory was previously unclear.

Purpose of the Study:

• To investigate the role of vHPC-PL projections in contextual fear expression following extinction.
• To determine if stimulating vHPC terminals in the PL affects contextual fear recall.

Main Methods:

• Optogenetics was used in rats to selectively stimulate vHPC terminals in the PL.
• Neuronal responses were recorded in anesthetized animals.
• vHPC-PL projections were stimulated in freely behaving rats during contextual fear renewal tests.

Main Results:

• Optogenetic stimulation of vHPC-PL projections activated approximately 12% of PL neurons in anesthetized rats.
• In freely behaving rats, stimulation during baseline context exposure reduced contextual fear post-extinction.
• This stimulation did not affect general motor activity or immediate fear responses after conditioning.

Conclusions:

• vHPC-PL projections play a significant role in modulating the expression of contextual fear after extinction.
• This pathway interaction is crucial for regulating fear memory, particularly in contexts previously associated with extinction.
• Findings contribute to understanding neural circuits involved in fear and anxiety disorders.