Chemogenetic Disruption of Monkey Perirhinal Neurons Projecting to the Rostromedial Caudate Impairs Associative...

Area of Science:

• Neuroscience
• Cognitive Science
• Primate Behavior

Background:

• Primates utilize stimulus-reward associations for foraging decisions.
• The rhinal cortex (Rh) and rostromedial caudate (rmCD) are crucial for assigning value to visual stimuli.
• Layer 5 neurons in the Rh project to the rmCD.

Purpose of the Study:

• To investigate the causal role of the projection from Rh to rmCD in learning and retrieving stimulus-reward associations.
• To determine if specific pathways within this system are critical for learning versus retrieval.

Main Methods:

• Reversible interruption of Layer 5 connections from Rh to rmCD in rhesus monkeys using a unilateral Rh lesion and inhibitory DREADD.
• Silencing of projection neurons from the perirhinal cortex (PRh) to rmCD via microinjections of deschloroclozapine.
• Assessment of effects on learned and newly acquired stimulus-reward associations.

Main Results:

• Interruption of the Rh to rmCD pathway had minimal impact on established stimulus-reward associations.
• Learning of new stimulus-reward associations was impaired when the Rh to rmCD connection was disrupted.
• Pathway-specific silencing of PRh to rmCD projection neurons significantly impaired the learning of new associations.

Conclusions:

• The learning of new visual stimulus-reward associations, but not their retrieval, critically involves projection neurons from the PRh to the rmCD.
• This pathway is essential for acquiring new value-based associations guiding behavior.