Axonal connections between S1 barrel, M1, and S2 cortex in the newborn mouse.

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Cortical Development

Background:

• Functionally interconnected brain networks are crucial for development.
• The anatomical basis of early corticocortical connections between somatosensory (S1, S2) and motor (M1) areas is not well understood.
• The subplate (SP) acts as a critical hub for sensory information in the immature brain.

Purpose of the Study:

• To investigate the anatomical substrate and functional connectivity of corticocortical projections between S1, S2, and M1 in newborn mice.
• To explore the role of the subplate (SP) in early sensorimotor integration.

Main Methods:

• Ex vivo carbocyanine dye (DiI) tracing in fixed newborn mouse brains to map axonal projections.
• Extracellular recordings using multi-electrode arrays in neocortical slices to assess functional connectivity.

Main Results:

• Neurons in M1 and S2 project to the SP of S1 barrel field (S1Bf), and vice versa, at postnatal day 0 (P0).
• Functional synaptic connections were detected between the SP and layer 5/6 (L5/6) within and between S1 and M1.
• Weak functional connectivity was also observed between S1 and S2.

Conclusions:

• Functional corticocortical connections between adjacent cortical areas, involving the SP and upper layers, are present at birth.
• The SP integrates early cortical activity, potentially shaping sensorimotor integration during early development.