The Baby’s Brain

Summary of “Life of Brain”, by Kathleen McAuliffe, Discover, June 30, 2007

Amniotic fluid is an excellent conductor of sound so that before birth, babies are attuned to the rhythm of the mother’s voice. Cultural assimilation begins before birth, impacting on the music liked and food chosen. Before birth we have many more brain cells and connections than we use as adults. Birth sparks more growth with new sights, sounds and sensations. Sights, sounds and touches are all activated together and the infant can’t tell which organ they come from. It is only with time and experience that they distinguish the inputs from the different sense organs. Heavily used pathways become coated in a fatty substance called myelin, which speeds transmission of information within the brain. Rarely used connections wither and die.

Half of the neural circuits toddlers have vanish by adulthood. There are “sensitive periods” in the brain when it is most receptive to stimulation. Infants are fascinated by anything that resembles a face. Newborns don’t see very well, but can see objects within a yard like an out-of-focus photo. By six months a baby can distinguish novelty in faces, but there is a window of time in infancy when the baby must be exposed to faces in order to become expert at distinguishing one face from another. Babies from four months old respond to different facial expressions. Real people’s faces work much better than photos.

Babies have the ability to perceive all of the basic sound units of all of the world’s languages. This facility is lost between 6 –12 months as circuits shrivel from disuse. Adults learning Hindi needed a year of training to make certain phonetic distinctions that a newborn readily makes. The key for a baby is watching a live speaker speak. Infants are more alert in social situations and learn meaning by following eye gaze. If no one engages them they treat language as if it were noise and tune it out. During the first year of life, as the baby goes from cooing to babbling to uttering the first word, parts of the brain that understand and produce speech begin to link up, babies drawing the connections between the movements of their lips and tongue and the sounds they make, allowing speech mimicry.

Our first memory dates from age 3 or 4 because the various parts of the brain are not yet connected, the reason we do not remember our infancy. If a child does not get appropriate sensory inputs at this early age or if the developmental process goes awry the result can be a “very funky wiring system”. The malleability of the young brain is a double edged sword. Learning occurs at a breathtaking pace but can be a liability if something goes wrong or the input is not what it should be.

Parents are the sculptors of their baby’s brain. Nothing beats hugs, kisses and lots of fun together.

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 development 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.