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Brains develop as the zygote's neural plate transforms into
the central nervous system of brain, spinal column and nerves.
The basic brain structure is formed by four months. Brain cells
(or neurons) are formed at an average rate of 250,000 per minute
throughout the nine months of gestation (the highest actual rate
is 500,000 per minute early in development, when most are created).
After formation, neurons migrate to function-specific positions.
Synaptogenesis, the process of forming synapses (or connections)
between brain cells, begins at two months' gestation and continues
to two years after birth, at a rate of 1.8 million connections
per second. Each cell must also grow dendritic branches. Dendrites
grow nobbins (dendritic spikes) to accommodate the synapses.
The growth of dendrites triples the thickness of the cerebral
cortex in the first year.
Myelination, the production of a lipid / protein which coats
each brain cell, enables the conductivity of cells. In fact,
until cells are myelinated, they are very poor at conducting
information. As Eliot points out, diet plays a key role in myelination,
especially in early childhood. Poor nutrition (such as low fat
intake) leads to poor brain function.
Each time a particular neuron is used, it is chemically excited,
cementing the connections between neurons (across the synapse)
from axon to dendrite. Repeated connections are kept; others
are pruned. This, Eliot argues, is where nurture plays a key
role in all areas of brain development.
Of course, the developing nervous system faces many dangers.
A genetically normal baby that is exposed to hazardous substances,
for instance, could be born with nervous system defects. But
hazardous substances don't necessarily effect all areas of the
developing brain. Since each separate function of the brain develops
at specific times, avoidance is largely a timing issue. (Eliot
includes a useful summary chart of pathogens.)
Birth itself is stressful and potentially dangerous, if the
baby is deprived of oxygen for too long. However, Eliot writes,
birth is usually a positive experience for newborns, clearing
their lungs for normal breathing and releasing stress hormones
that help them adjust to their new environment.
Development of the Senses
After the basic
structures of the brain are formed, the senses begin to develop.
This is a particularly important stage, because the senses allow
input into the brain and actually determine how the brain evolves.
Touch is the first sense to develop during gestation. As Eliot
notes, it encompasses four types of sensory abilities: cutaneous
sensation (touch on the skin), temperature, pain and proprioception
(sense of position and movement in one's body). These are all
functional at birth. Cortical size, as well as emotional well-being,
can be increased by tactile stimulation (baby massage, playing
with toys, exposure to different textures).
The vestibular system, which controls reflex and motor skills,
is located inside the middle ear. This sense is important to
the development of other brain functions because the earlier
babies can explore the world, the quicker they will learn.
Smell is a primitive sense, and it is extremely important
to other mammals. In humans, it is mature at birth. Fetuses can
smell in the womb during the last trimester. This promotes bonding
of the infant to the mother after birth. Infants also recognize
the smell of their mother's breast.
Fetuses are also capable of tasting in the womb. Taste preference
is malleable, but all babies prefer sugar since it satisfies
their taste abilities at birth. Eating sweet foods releases endogenous
opiates in the brain that induce a sense of pleasure and well-being.
Sour-preferring cells in the tongue are the last to develop.
(Eliot's examination of food requirements and how they differ
for children and adults is particularly thorough.)
Vision, on the other hand, is poor in humans at birth. Many
other animals have better vision at birth because it is beneficial
in species that require early independence. For humans, though,
the lack of early visual skills encourages infants to stay close
to their caregivers. Experience, Eliot writes, controls the wiring
of our visual cortex. The lack of visual stimulus, for example,
can hamper later development of hand-to-eye coordination, and
problems such as crossed eyes can deprive a child of binocularity.
Since we are visually centered animals, a child's visual experience
is important in shaping the rest of his mind.
But the most important sense for intellectual development
may be hearing because it leads to the development of language.
It also strongly influences emotional development. Hearing begins
in the womb and is very advanced at birth, so early detection
of hearing impairment can avoid detrimental effects to children's
language skills.
Emergence of the Mind
The development
of emotions, memory and language is dependent on experience as
well, as Eliot demonstrates. Success in later life may stem more
from children's emotional intelligence than their IQs. Tests
for impulse control in four-year-olds are a better predictor
of later high school success than the IQ test, for example.
Language has its own apparatus, like an "extra chip"
for humans. Humans have two distinct regions that process different
aspects of language (verbs and grammar versus nouns and meanings).
This shows that language is innate in the human species. All
languages share a "Universal Grammar" ( as Noam Chomsky
has argued), and it is grammar that sets human language apart
from other animal communication.
Although the capacity for language is instinctive, the particular
language we each master is a function of experience. Verbal skills
of infants and children can thus be improved by conversation.
Intelligence
There are many
areas of human intelligence, only one of which is measured by
the IQ test. "The logical conclusion," Eliot argues,
"is that there is no single type of intelligence, but many
different ones, and the concept 'intelligence' becomes a synonym
for excellence in any single area."
Brain size isn't everything, either. Intelligence is based
on speed, efficiency of use and memory capacity as well. And
all factors except brain size can be improved with proper stimulation.
According to many studies, genes contribute about fifty percent
towards a human's intelligence as measured by the IQ test. The
remainder is environmentally determined. Early experience--proper
nutrition, a stimulating environment, and a nurturing parent
/ caregiver style--is critical to a child's later intellectual
potential. As Eliot writes, experience
rewires the brain. Whether early in a baby's life or well
into old age, active synapses and pathways continue to be strengthened,
and inactive ones weakened, according to the sights, sounds,
feelings, and events of daily life. Learning, then, is really
just an extension of development, a later manifestation of the
remarkable ability of each individual's brain to modify itself
according to his or her unique experiences.
What's Going On
in There? is a fascinating book, rich in detail and advice.
Eliot is particularly good at raising awareness of the dangers
as well as the benefits to developing brains. (Not surprisingly,
she encourages an active role in upbringing.) Her study has
the potential to help all parents and children. Of course, much
of the book's market will undoubtedly be well-read parents who
are already prepared for informed child rearing, but teachers
of young children should also find it useful.
Luckily for such a complicated subject, Eliot's style is straightforward
and clear. While she doesn't talk down to her readers, she simplifies
enough to enable non-scientific individuals to understand the
general concepts, even if they don't memorize the particular
terms. Numerous charts and graphs help (as does the index). A
glossary would have been a nice addition, but its absence doesn't
detract overall.
This should be required reading for anyone interested in realizing
their child's potential.
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