Circuit-Based Corticostriatal Homologies Between Rat and Primate.

Area of Science:

• Neuroscience
• Comparative Anatomy
• Primate and Rodent Brain Research

Background:

• Understanding psychiatric disorders necessitates animal models, but frontal-striatal homologies between rodents and primates remain unclear.
• The striatal emotion processing network (EPN), comprising nucleus accumbens shell, hippocampus, and amygdala projections, is conserved across species.
• Investigating conserved networks like the EPN and their connections with the anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC) can reveal cross-species similarities.

Purpose of the Study:

• To assess network similarities between rat and monkey brains by examining the relationship between the striatal emotion processing network (EPN) and projections from the anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC).
• To identify homologous brain regions and connectivity patterns across species to improve the translation of findings from animal models to human pathology.

Main Methods:

• Comparative analysis of the location and extent of EPN components in rats and macaques.
• Anatomical tracing using anterograde injections in the ACC/OFC of rats and monkeys to map corticostriatal terminal fields.
• Assessment of the overlap between ACC/OFC projections and EPN components within each species.

Main Results:

• The core components of the EPN exhibited similar locations and sizes across rats and macaques.
• Extensive overlap was observed between ACC/OFC terminals and EPN components, particularly with projections from the infralimbic cortex in rats and area 25 in monkeys, supporting OFC topography homology.
• Dorsal ACC displayed distinct connectivity profiles between rats and monkeys, indicating species-specific differences.

Conclusions:

• The infralimbic cortex in rats and area 25 in monkeys are likely homologous regions based on their connectivity with the EPN.
• Evidence suggests homology in the orbitofrontal cortex (OFC) across species.
• Segmentation of the monkey and rat striata based on ACC/OFC inputs and identification of striatal hubs facilitate the translation of findings between rodent models and human psychiatric disorders.