The emergence of architectonic field structure and areal borders in developing monkey sensorimotor cortex

Area of Science:

• Neuroscience
• Developmental Biology
• Comparative Anatomy

Background:

• The adult monkey sensorimotor cortex exhibits distinct structural and functional areas.
• Understanding the developmental trajectory of these areas is crucial for comprehending brain organization.

Purpose of the Study:

• To investigate the developmental sequence of architectonic features and borders in the monkey sensorimotor cortex.
• To identify the timing and mechanisms of area differentiation during fetal and postnatal development.

Main Methods:

• Utilized Nissl staining, cytochrome oxidase, and acetylcholinesterase histochemistry.
• Employed immunocytochemistry for GABA and neuropeptides (somatostatin, neuropeptide Y, substance P, cholecystokinin).
• Examined specimens from fetal, postnatal, and adult monkeys.

Main Results:

• At E110, somatic sensory cortex lacked parcellation but showed incipient borders via chemo- and immunocytochemistry.
• Motor cortex at E110 differed from adults with a prominent layer IV and a detectable border between areas 3a and 4.
• Architectonic features and areal borders matured gradually, becoming adult-like by early postnatal stages.
• Changes in cytoarchitecture paralleled the redistribution of GABA and neuropeptide-immunoreactive cells and fibers.

Conclusions:

• Progressive refinement of cytoarchitectonic features and neurotransmitter/peptide distributions occurs mainly in the last trimester of gestation.
• These developmental changes coincide with afferent axonal system ingrowth.
• Establishing neural connectivity may influence structural and molecular phenotypes within developing cortical areas.