by Patrick Yang

The cerebral cortex is the outermost layer of the brain and is responsible for advanced processes, such as complex emotion, that distinguish humans from other animals. A key component in cortex development is prenatal neural migration, the movement of neurons before birth, which begins early on in the embryo. These migratory neurons, or Arc neurons, originate near areas of initial development called “zones of proliferation” that are located near the center of the brain. Arc neurons eventually migrate from zones of proliferation to their final destination in the cortex, where they differentiate and form neural circuits.

A longstanding belief in the scientific community is that neural migration is completed in the womb. However, Dr. Mercedes Paredes and his team at University of California, San Francisco recently challenged this theory by presenting data supportive of the migration of neurons into the cerebral cortex two years after birth. In Paredes’ study, brain tissue aged 0 to 7 months from the Pediatric Brain Tissue Bank was marked with a stain that identified doublecortin, an identifier for migratory neurons. The stained brain tissue was visualized under brain MRI and showed prominent neural movement in brain tissue aged two-months-old and younger. Signs of migration decreased in older brain tissue and showed drastic decrease in seven-month-old tissue. However, slight migration was still evident in two-year old brain tissue.

Neurons are still migrating during the first several months after birth, indicating that infants are still developing their neural circuits. Thus, postnatal migration of neurons suggests the fragility of the infant brain and the importance of proper care of the baby during the first several months after birth. Any damage to the brain during this developmental stage can explain the origin of several neurological disorders, such as epilepsy, cerebral palsy, and autism.

References:

1. M.F. Paredes et al., Extensive migration of young neurons into the infant human frontal lobe. Science 354 (2016). doi: 10.1126/science.aaf7073.
2. Image retrieved from: https://www.flickr.com/photos/fbobolas/3822222947