Reward-Related Expectations Trigger Dendritic Spine Plasticity in the Mouse Ventrolateral Orbitofrontal Cortex

Area of Science:

• Neuroscience
• Decision-making
• Cellular plasticity

Background:

• Goal-directed decision-making relies on predicting action consequences.
• The orbitofrontal cortex (OFC) and dendritic spine plasticity are implicated in this process.
• Understanding the specific role of spine morphology in OFC function is crucial.

Purpose of the Study:

• To investigate the relationship between dendritic spine morphology in the OFC and action-outcome expectation updating.
• To determine the causal role of OFC dendritic spine plasticity in behavioral flexibility.

Main Methods:

• Behavioral training in mice (contingent vs. non-contingent reinforcement).
• Chemogenetic inactivation of the OFC to block action-outcome updating.
• Viral-mediated knockdown of Fmr1 in the ventrolateral OFC.
• High-resolution microscopy to analyze dendritic spine morphology.

Main Results:

• Successful action-outcome learning and updating were associated with fewer thin spines and more mushroom spines in the ventrolateral OFC.
• OFC inactivation impaired action-outcome conditioning.
• Fmr1 knockdown in the OFC mimicked inactivation effects and led to excess thin spines.

Conclusions:

• A balanced ratio of mature to immature dendritic spines in the OFC is critical for selecting actions based on anticipated consequences.
• OFC dendritic spine plasticity plays a necessary role in behavioral adaptation and expectation updating.
• Constraining spine formation while maintaining mature spines may solidify durable expectations.