Washington: A new study has revealed that the actual act of birth in mice causes a reduction in a brain chemical called serotonin in the newborn mice, triggering sensory maps to form.
The findings shed light on the key role of a dramatic environmental event in the development of neural circuits and reveal that birth itself is one of the triggers that prepares the newborn for survival outside the womb.
Study's author Hiroshi Kawasaki of Kanazawa University in Japan said that their research clearly demonstrates that birth has active roles in brain formation and maturation.
"We found that birth regulates neuronal circuit formation not only in the somatosensory system but also in the visual system. Therefore, it seems reasonable to speculate that birth actually plays a wider role in various brain regions," the researcher said.
Mammals ranging from mice to humans have brain maps that represent various types of sensory information
Researchers found that the birth of mouse pups leads to a drop in serotonin levels in the newborn's brain, triggering the formation of neural circuits in the barrel cortex and in the lateral geniculate nucleus (LGN), a brain region that processes visual information.
When mice were treated with drugs that either induced preterm birth or decreased serotonin signaling, neural circuits in the barrel cortex as well as in the LGN formed more quickly.
Conversely, neural circuits in the barrel cortex failed to form when the mice were treated with a drug that increased serotonin signaling, suggesting that a reduction in levels of this neurotransmitter is crucial for sensory map formation.
Because serotonin also plays a key role in mental disorders, it is possible that abnormalities in birth processes and the effects on subsequent serotonin signaling and brain development could increase the risk of psychiatric diseases.
The study is published in the journal Cell Press.