VTA Excitatory Neurons Control Reward-driven Behavior by Modulating Infralimbic Cortical Firing

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Computational Neuroscience

Background:

• The medial prefrontal cortex (mPFC) exhibits functional differences in punishment versus reward tasks.
• The infralimbic cortex (IL) within the mPFC is associated with behavioral suppression.
• The ventral tegmental area (VTA) is crucial for reward and aversion learning, but its connection to IL reward encoding is unclear.

Purpose of the Study:

• To investigate the role of VTA excitatory neurons in IL encoding of reward-related behaviors.
• To elucidate the population-based mechanisms underlying reward acquisition and association in the IL.
• To determine how VTA glutamate neuron activity influences IL firing rates and behavioral responses to rewards.

Main Methods:

• Recording neuronal activity in the IL during reward-seeking tasks.
• Manipulating VTA glutamate neuron activity using chemogenetics (inhibition).
• Analyzing firing rate (FR) changes in IL ensembles during reward acquisition and omission phases.
• Assessing behavioral affinity for previously rewarded targets.

Main Results:

• IL ensembles showed broad firing rate suppression during reward acquisition and expectation.
• This FR suppression persisted after reward-linked events.
• Inhibiting VTA glutamate neurons during reward acquisition weakened reward-target associations, indicated by reduced affinity and altered IL neuronal activity patterns.
• Fewer IL neurons exhibited FR decrease, and more showed no change when VTA glutamate was inhibited.

Conclusions:

• VTA glutamate neurons play a critical role in establishing IL inhibitory states essential for encoding reward acquisition.
• These VTA-IL interactions are vital for forming and expressing reward-target associations.
• The findings highlight a neural mechanism by which reward learning is processed in the brain.