Scientists at the University of California, Berkeley, have been listening to the communications of brain cells of developing human embryos. When an embryo is between 6 and 12 weeks old, the neurons begin chanting. The harmonized signals actually change the shape of the brain and the circuits giving the child its mental abilities.
The discovery that the communications of the neurons actually configures the physical structure of the brain, like waves create ripples in the sand, inverted the entire orientation of neuroscience.
Before, scientists assumed the structure of the brain dictated the pathways of communication and that the rhythmic firing of the neurons was a by-product of the chemical/genetic construction of the brain.
Now they realize the pattern of communications construct the brain. What's more, the communications of the 100 billion neurons continue the process of building the brain and shaping its pathways well after birth.
When a human embryo is in its third week, a layer of cells folds inward to produce a fluid filled tube. The cells of this neural tube develop at a rate of about 250,000 new cells a minute (a minute!). Over the next few weeks, the brain and spinal cord are shaped from the smoothly choreographed dance of these cells. And the cells coordinate their dance by their combined digital, rhythmic electrical pulses - like musicians and dancers time beat time with drums. The digital beats are modulated by smooth tones of chemical signals produced when particular cells are exposed to differing environmental conditions within the rapidly growing embryo.
The constant intercommunications between cells goes deep. The information activates genes within the cells that, in turn, stimulate the production of special proteins. These are, in turn, liberated into the cellular environment as responses. This chemical, in turn, is detected by other neurons and it stimulates their genes to produce direct them to behave in special ways. Like growing tentacles this way or that and amplifying or muting their own molecular productions or electronic chanting. Or even migrating through the countless billions of developing tissue cells to establish pathways for future nerves throughout the body.
Each neuron has a cluster of short bushy tentacles called dendrites that bring messages into the cell. A longer axon tentacle that carries its response messages to other cells, often far distant in the body. Information comes in via the dendrites, out via the axon.
Neurons in the brain grow their axons out into the developing embryo tissues, following exact routes to reach their destinations. As the tentacle grows, it follows a "growth cone." This looks like an ameba and has highly sophisticated sensory systems, like molecular sonar and radar, to scan the environment for special protein sign posts tacked out by other cells. Some of these molecular (protein) sign posts are attractants and others are repellants.
Neurons collaborate closely when they send off their axons into the developing body tissues. They bundle their tentacles together neatly as nerves. Near the brain, where they all start from, the nerves are big trunk lines with millions of axons arranged side by side. Down in the body these divide into smaller nerves to go to specific regions of the body and there they divide again and again, like branches of a tree, until finally the axon needed to excite a particular muscle cell - like the one that twitches the big toe up - is all alone.
The tentacle seeks out its specific muscle cell and slaps a synapse onto it. When the person decides to lift the big toe, the neuron in charge of this sends an electric pulse (generated by a sodium potassium flux through the cell wall of the axon) down its axon tentacle all the way to the synapse pad. There, the digital electric pulse stimulates tiny organelles in the neuron's cell wall to produce chemical messengers that transmit the signal to the muscle cell. And the muscle cell contracts, and the big toe goes up.
Researchers in Berkeley discovered that axons growing outward to attach to muscle cells were kept together as a nerve by a specific gene. When the target muscle mass was reached and the first connections made, the electrical firing of the neurons suppressed the gene and the axon tentacles divided out into the muscle cells, each seeking unoccupied sites, then firing when they connected.
The firing not only told the "stick together" gene to shut down, it also stimulated another gene to send out orders into the cell to produce a chemical known as CREB. CREB molecules regulate the development of memory traces. Without it, the cells - and the organism - cannot form long term memories.
Once the connections are made between the neurons and between neurons and sensory and muscle cells, the activity, the communications themselves, determines how the neurons organize themselves and their connections.
What starts out as a disorganized mess is, once activities begin, quickly organized into neatly arranged nerves and ganglia. First everybody just gets there, forming a toe-hold so to speak, then they shuffle about getting their act together.
At birth, the brain has as all the nerve cells it will ever have, laid out in circuits primed for the development of vision, language, walking, moving muscles, and so on. When the infant is forced out of the womb, a flood of information from the environment stimulates the billions of sensory receptors. The receptors light up the brain's switchboard with the news of the outside world, every one of them excited, sparking off digital electronic yows at the top of their capacitance.
The neurons respond by a furious growth of tentacles. Like a heady electronic zap will make hair stand on end. The new tentacles whip out in all directions as the neurons grab each other, making trillions of new connections. By the age of two, the brain has twice as many synapses and uses twice as much energy as the brain of the normal adult. Not that the kid's parent would be able to guess that while changing diapers and making funny high pitched cooing noises.
In the visual cortex, synapses increase from about 2,500 per neuron at birth to 18,000 per neuron six months later. In other areas of the cortex, synapses average around 15,000 per neuron from the age of two until the age of 10 or 11. Here is an animation showing a neuron growing tentacles.
Connections that are used become stronger. Those not used are withdrawn. Repeated experience sends bursts of signals through specific pathways knitting neurons into well defined circuits.
When an infant gets worked up over something, the neurons do too, urging genes to produce more RNA that in turn speeds up the cellular manufacture of proteins and enzymes used to process and store information.
Environmental signals become neuronal communications and these, in turn, are processed by the genetic memory system to promote the growth and attachment of new tentacles and the increase of memory storage capacity within the cell.
What this means is that there is an interchange of two kinds going on.
First the neurons do something, like grow their axon tentacles out into the little fingers of the developing embryo. But before they can do anything else, they have to arrange themselves, check out they are in the right place.
The brain requires feedback from the environment to be sure it is developing correctly.
If these checkpoints don't happen, the developing cells are no longer sure of their position or expected responses and development can be severely upset. For example, children born with a cataract will become permanently blind if the clouded lens is not removed because the brain's visual center requires sensory stimuli from the retina of the eye to organize itself.
The checkpoints form a series of "windows of opportunity" for developing various neurological functions. During these periods of development and performance checking, the more information supplied by the environment, the better the system is tuned. Sit up and take notice of that fact, because it has obvious practical implications. Such as:
Basic motor skills develop from birth to age three, from jerky, uncontrolled movements to progressively refined movements. At two months the motor-control centers are sufficiently developed for an infant to reach out and grab an object.
Fine motor ability begins to develop from age 3 to age 10 and musical fingering from age 6 to 10. If a child is encouraged to use all of its muscles and develop fine control through various exercises, like musical training, while this development process is in full swing, it will become far more adept than a child who is not able to try and develop its muscular control.
By 12 months the speech centers are ready to begin the process of language.
Babies can see at birth but the ability to focus both eyes on a single object and fine detail develops progressively to the age of 5 and then the window begins to close. By four months the connections for depth perception are established. Binocular vision begins its fine tuning at about six months and is fully developed by age three. If vision problems are not corrected before three to five, the child may never be able to see properly. If a child is encouraged to practice depth perception and seeing fine details and patterns, it will have better neurological equipment later in life for these abilities.
(if you are interested in learning more, go to the section on "behavior guides". )
Emotions go through windows of development.
From birth until three years old the stress and contentment response is especially sensitive to development.
After six months, stress and contentment shifts into more complex feelings of joy and sadness, attraction and fear.
This is the forward (moving towards what it wants), backwards (retreating from what it fears) stage. During these years, the child learns strategies to attain what it desires and escape from what it fears.
Children exposed to stress and fear at this age become highly tuned to stress and may develop an array of defensive behavior systems.
This is also the time we develop our ideas on sexual attractiveness. We get imprinted on the the kind of face, figure, voice, smell, that one day we will flip out over and get married to.
Envy and empathy, begin to develop from two to 10,
along with pride and shame.
This is the up (I am better than you) and down (you are better than me) phase.
During this phase, children learn their position on the pecking order in life. They test themselves against others and against various situations to determine what they can dominate and what dominates them.
This is also the time we get imprinted on nature, if we do. There comes a time - a moment - when we become aware of the larger world; beyond ourselves, beyond our family, out beyond all the people and pets in the world. A wild world filled with butterflies, birds, plants of all kinds, crabs, fish, an ocean of other creatures. When this happens it can change our lives forever. If it happens. Hard for a kid in the inner city to get imprinted on nature, but it does happen.
Language has a series of windows.
If syntax is not learned before the age of five or six a child will never be able to speak coherent sentences.
The window for learning new words stays open throughout life, but the ability to learn a second language is greatest between birth and six. So start your children learning a second language at 4, not 14.
Cleaning up the system
At around ten, the balance between synapse formation and atrophy shifts and those circuits not used are withdrawn permanently.
This is the period of self testing against the social environment; the right (am I doing it right?) versus the left (am I doing it wrong?) phase.
Teenagers carve away their own personalities and talents and at the same time, their brain cells respond by strengthening the communication links that get used most and removing synapses that are used less often or not at all.
By 18, the synapses have been reduced in numbers but those left become stronger and more adept at their communications.
Neurologists liken the period from birth to 10 as the formation of a huge block of material and the period from 10 to 18 to a sculptor clearing away excess material to reveal the talents and abilities of the person.
Time magazine heralded these discoveries as the most important medical findings of the decade. The single most important finding is the discovery that the combined wave-like signals between the neurons in the human embryo actually shape the physical shape of the brain.
The shaping of the brain and the whole nervous system by a cyclic process of response, checking the effect of this action against expected results, and then organizing the next response is the 4 phase process of becoming - mind - in action. Mind generates form and function. And not just in the brain.
The practical implications of brain development are this: If you know the windows of opportunity and give your child the maximum opportunity to exercise the noggin at the right times, your child will be smarter, more dexterous, and maybe even nicer than one that is neglected. Children who, for example, learn a musical instrument between the ages of 6 and 10 come out of the training with brains 20% bigger than kids who don't get to do all that complicated coordination.