Barrels and septa: separate circuits in rat barrels field cortex

Area of Science:

• Neuroscience
• Sensory processing
• Cortical circuitry

Background:

• Neural circuits in sensory cortex dictate functional properties.
• Sensory inputs are integrated through diverse cortical pathways.
• Rodent whiskers are represented in somatic sensory cortex (S-I) via distinct barrel and septal columns.

Purpose of the Study:

• To investigate the intrinsic and corticocortical circuitries originating from barrel and septal columns in rodent S-I cortex.
• To determine if parallel subcortical pathways for whisker input are maintained as segregated pathways within the cortex.

Main Methods:

• Utilized small biocytin injections in rodent S-I cortex.
• Traced intracortical and corticocortical projections from barrel and septal columns.
• Analyzed the termination patterns and distances of these projections.

Main Results:

• Barrel columns exhibit short-range intracortical projections within S-I and project to S-II cortex.
• Septal columns display longer-range intrinsic projections, extending to neighboring septal columns.
• Septal columns also project corticocortically to S-II, dysgranular cortex, and posteromedial parietal cortex.
• Septa serve as primary conduits for lateral intracortical connections, unlike isolated barrels.

Conclusions:

• Distinct intrinsic and corticocortical circuitries arise from barrel and septal columns.
• The parallel subcortical pathways for whisker input are maintained as partially segregated pathways within the cortex.