Rostral and caudal basolateral amygdala engage distinct circuits in the prelimbic and infralimbic prefrontal cortex

Area of Science:

• Neuroscience
• Circuitry of the brain
• Amygdala-PFC interactions

Background:

• Basolateral amygdala (BLA) to medial prefrontal cortex (PFC) connections are crucial for memory and emotion regulation.
• Disruptions in these pathways are implicated in neuropsychiatric disorders.
• The diverse functions suggest complex, nested circuits within the BLA-PFC network.

Purpose of the Study:

• To delineate the specific circuits through which the rostral BLA (rBLA) and caudal BLA (cBLA) project to prelimbic (PL) and infralimbic (IL) PFC subregions.
• To identify the targeted neuronal subtypes within the PFC by distinct BLA regions.
• To understand how these BLA-PFC circuits influence local PFC activity.

Main Methods:

• Retrograde and anterograde anatomical tracing to map BLA projections.
• Ex vivo whole-cell recordings and optogenetics to assess neuronal subtype targeting.
• In vivo silicon probe recordings and optogenetics to confirm circuit activation.
• Soma-tagged optogenetics to investigate local PFC circuit dynamics.

Main Results:

• The rBLA preferentially targets layer 2 (L2) cortico-amygdalar (CA) neurons in the PL.
• The cBLA primarily drives layer 5 (L5) pyramidal tract (PT) neurons in the IL.
• rBLA activation influences both PL L2 and, polysynaptically, PL L5 neurons.
• cBLA influences IL L5 neurons, while rBLA primarily activates PL L2 neurons.

Conclusions:

• The study successfully maps distinct BLA subregion projections to specific PFC subregions and neuronal layers.
• These findings highlight how the BLA differentially engages separate PFC circuits.
• Understanding these precise pathways provides insight into the neural basis of emotion and memory regulation and potential therapeutic targets.