Q&A About a Baby's Brain

(Adapted from “Frequently Asked Questions”, Zero To Three, 6/3/08)

It is important to understand the brain development of babies if disability is to be prevented or decreased in severity. Young children are more open to learning and enriching experiences, while also more vulnerable to poverty and poor parenting.

Nature and nurture - which is more important?
Genes from the parents form all of the cells and general brain connections.  Nurture fine-tunes those connections.

Does Experience Change Actual Brain Structures?
Yes. Brain activity is “activity-dependent so that input shapes how brain circuits are put together. Every experience, no matter how small, excites specific neural circuits, leaving others inactive. Those repeated over and over again strengthen these circuits, while unused circuits drop away.

What is a "Critial Period" in Brain Development?
Babies require normal visual and language input in the first few years or the language- learning window begins to close about five years of age.

Are there critical periods in the development of every brain function?
Probably not but much about this is unknown.  Visual and language development are known to be sensitive to early life experience.  We know less about emotional functioning, math or musical ability. Social-emotional development depends on a positive, nurturing caregiver.

When is the brain fully developed?
Never. Brains are continually reshaping themselves to meet demands of everyday life throughout adulthood. But certain brain structures do level off during development. New evidence shows that new neurons are produces throughout life. A newborn’s brain is about a quarter the size of an adult’s, growing to 80% of size by age three, and 90% of size by age five. Brain development is also measured by the speed of neural processing, those structures continuing to mature until about age 30.

Does nutrition affect the developing brain?
Yes, especially between mid-gestation and age two. Malnourished fetuses and infants suffer lasting behavioral and cognitive deficits, with slower language, fine motor development, lower IQ, and poorer school performance. Breast milk offers the best mix of nutrients for brain growth.

When does brain development end?
The neural tube that becomes the central nervous system begins at 16 days after conception, forming a groove at 18 days that begins to shut into a tube about 22 days. By 27 days the tube begins to transform into the brain and spinal cord.

When does the fetus brain begin to work?
By the sixth week after conception early neural connections permit the first fetal movements. Limb movement occurs around eight weeks, fingers at ten weeks, and hiccupping, stretching, yawning, sucking, swallowing, grasping and thumb sucking by the end of the third month. The second trimester begins rhythmic breathing movements, heart rate and blood pressure. Last to mature is the cerebral cortex.  This is responsible for conscious experience, voluntary actions, thinking, feeling and remembering.

What are the most important influences on brain development before birth?
Good nutrition of the mother, avoidance of smoking and alcohol, and forms of radiation. However, infections pose the greatest risk, ranging from German measles to sexually transmitted diseases.

How developed is the brain by birth?
The lower parts of the brain are vital to bodily functions- breathing, heartbeat, circulation, sleeping, sucking and swallowing. Higher portions of the brain (the limbic system and cerebral cortex) are still very primitive, maximizing opportunity for a baby’s experience and environment to shape an emerging mind.

Are there any differences in the deveopment of boys' and girl's brains?
Yes, but they are subtle. Each uses the two halves of the brain differently, and males have slightly larger brains. Differences are seen from the moment of birth. By three months, boys’ and girls’ brains respond differently to speech for reasons that are not clear. Girls are slightly more advanced in vision, hearing, memory, smell and touch, as well as being more socially attuned. Boys eventually catch up and generally out perform girls by age three in puzzles and certain eye-hand coordination.