Pre-synaptic control of remote fear extinction in the neocortex

Area of Science:

• Neuroscience
• Molecular Biology
• Memory Research

Background:

• Remote memory consolidation involves changes in immediate early genes (IEGs), GAP-43 expression, and dendritic spine morphology in the anterior cingulate cortex (aCC) and infra-limbic cortex (ILC).
• Remote memory extinction impacts these structural changes differently across brain regions, with the aCC showing density resets and the ILC forming new spines.

Purpose of the Study:

• To investigate whether IEGs and GAP-43 expression also exhibit region-specific changes following remote memory extinction.
• To elucidate the pre-synaptic adaptations in the aCC and ILC associated with remote fear memory extinction.

Main Methods:

• Contextual fear conditioning in mice.
• Analysis of c-Fos induction (an IEG) and GAP-43 protein expression in the aCC and ILC at 36 days post-conditioning.
• Assessment of changes following remote memory extinction.

Main Results:

• Remote memory extinction decreased c-Fos induction in both the aCC and ILC.
• GAP-43 expression remained unchanged in both regions after extinction.
• These findings indicate similar, protein-specific pre-synaptic adaptations in aCC and ILC neurons.

Conclusions:

• Remote memory extinction induces region-specific pre-synaptic adaptations, characterized by altered IEG induction but stable GAP-43 expression.
• Combined with previous findings on post-synaptic changes, these results reveal a complex pattern of neocortical alterations driven by extinction.
• These adaptations may support context-dependent fear memory erasure or reinstatement.