Early Brain Development

During development, a baby's brain is a maze of neurons much different in structure from the adult's brain. One interesting example is vision development. To develop vision, nerve fibers from the retina must grow to extend far enough through the brain to reach the visual thalamus (see Figure 2-2), and from there, axons reach to the outer layers of the cortex, before the cortex even exists.

cortex—the folded outer layer of the brain

A study by Carla J. Shatz,6 professor of neurobiology at Stanford University, demonstrated the existence of transient support "scaffolding" in the developing brain that aids in developing vision but disappears after the brain's growth is finished. Special types of neurons, subplate neurons, suddenly appear just below the final destination at the visual cortex and function to bolster and direct the axons to their proper location. Then these subplate neurons disappear. These and other neurons that act as temporary support structures, along with the proteins and chemical cues previously mentioned, prevent the axons from wandering into incorrect areas and impairing brain functions. Some disabilities, such as cerebral palsy, autism, epilepsy, schizophrenia, and dyslexia are thought to be a result of wandering axons or improper connections.7

LEFT VISUAL FIELD RIGHT VISUAL FIELD

Temporal Nasal Nasal Temporal

Temporal Nasal Nasal Temporal

Visual cortex

Figure 2-2 Pathway from retina to visual cortex

Visual cortex

Figure 2-2 Pathway from retina to visual cortex

At birth, the brain weighs approximately three-quarters of a pound. The migrating axons have reached the correct general area but not necessarily the exact site. The neurons in the visual cortex alone form about 2,500 connections per neuron at birth, and with proper stimulation, this rapidly increases to 18,000 connections per neuron after about six months. Stimulation, including touching, speaking to the baby, and presenting different images, helps the brain increase efficiency and select correct sites. Research demonstrates that babies who are not stimulated have brains 20 percent to 30 percent smaller than normal.8 This process of stimulation and mental reaction is much like fine-tuning a station on the old-style radio dial: If the message gets close to the proper site, but not exactly where it needs to be, the result is not as clear as if the tuning were exact. Each time the message is sent, the tuning becomes more effective, until at last, with sufficient testing of the connections, the signal is processed clear and free of static.

From birth, the baby learns to be efficient at transferring auditory, visual, and/or kinesthetic information. As you read to a child and point out the words, you are stimulating the auditory and visual aspects of learning. Taking a child's hand and tracing the letters reinforces the kinesthetic qualities. It is important that the child is exposed repeatedly to all the learning preferences in order to fine-tune the circuits used for each technique (more on that in just a bit). The more techniques the child can call upon during the school years, the more likely the child will be considered a success in the traditional school setting. The traditional school setting primarily supports visual and auditory learners.

As the brain learns what the correct representations are and which paths are most efficient at transmitting this information, it keeps the most-effective pathways and prunes the less-efficient ones. Connections, which are used on a regular basis and thus become fine-tuned, are retained, while other connections, which are inefficient or not used at all, are eliminated.9 As many as 600 connections may be eliminated per second during this pruning period. After the synapses and axons are operating correctly, the efficiency of the mental processing is dependent on genetic, environmental (including nutritional and sociological), psychological, and educational factors.10

The time after birth is extremely critical. For the first couple of years, the child's brain is most malleable. After approximately 8 to 10 years of age, the brain is not as adaptable to change. That is why young children who suffer brain injuries recover more quickly and completely than adults with the same brain injuries. We begin to develop our learning preferences before we reach school age. We already know whether we like to learn and how we want to go about it before we ever reach kindergarten. This is why the quality of the interactions of the parents or caregivers with the child are extremely critical to the learning process and the future success of the student. If you have been successful in learning in formal school settings, you probably are successful in real-life settings such as your job. If you have been unsuccessful in learning in the past, or if you are experiencing difficulty holding on to information from day to day, you can improve your capabilities. You can literally "change your mind" and be more efficient and reliable. But assuming you are an adult, you need to know the facts about how your brain operates in order to affect the processes. Please keep reading...

The Adult Brain

By the time the baby becomes an adult, the brain weighs approximately three pounds. This increase in weight is due to the increase in neuron size and the tremendous increase in the number of connections formed among the neurons since birth. Imagine trying to take billions of neurons formed in layers and trying to fit them into the skull. It is similar to trying to fit a piece of newspaper into a small box. Crumpling it in on itself would be a good solution. The layers of neurons form the gray matter and enfold the trillions of axons passing through the brain and interconnecting the neurons. The myelin sheaths covering the axons are white; this region therefore is described as white matter.11 The cortex makes up 80 percent of the brain's volume and is the convoluted mass normally imagined when the word "brain" is mentioned.

Figure 2-3 Top view of the brain showing both hemispheres

The grooves and folds, named sulci and gyri, respectively, that appear on the surface of the cortex are used as landmarks or reference points to locations within the brain (see Figure 2-3).

sulci—grooves in the cortex gyri —folds in the cortex

One of the deepest of the sulci divides the cortex from the front to the back into two hemispheres. The two hemispheres are connected primarily by a thick bundle of nerves named the corpus callosum, (See Figure 2-4).

Just as bodies have the same general configuration (the head bone's connected to the neck bone, the neck bone's connected to the shoulder bone ...), everybody's brain has the same anatomical parts. Each of us has two hemispheres, a corpus callosum, grooves, and folds. These grooves (sulci) and folds (gyri) are so standardized in location that they are used as landmarks or reference points to locations and activities within the brain.

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Figure 2-4 The hemispheres and their bridge, the corpus callosum Brain Function Location

Some functions carried out by the brain have been identified as to location. The more basic functions of life, such as breathing, are located close to the base and the spinal column in the brainstem. The cortex handles the higher-reasoning skills, such as language, math, and musical abilities; and the appreciation of humor.

Corpus ^ Callosum

Figure 2-4 The hemispheres and their bridge, the corpus callosum Brain Function Location

Some functions carried out by the brain have been identified as to location. The more basic functions of life, such as breathing, are located close to the base and the spinal column in the brainstem. The cortex handles the higher-reasoning skills, such as language, math, and musical abilities; and the appreciation of humor.

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