Brain-Introduction

6 Des


“The stuff that drives scientists into their laboratories instead of onto the golf links is the passion to answer questions, hopefully important questions, about the nature of nature. Getting a fix on important questions and how to think about them from an experimental point of view is what scientists talk about, sometimes endlessly. It is those conversations that thrill and motivate.”
Neuroscientist Michael Gazzaniga

INTRODUCTION
As educators and parents become more cognizant of the impact they have on the growing brain, they often begin asking, “How does the human brain work and what can I do to nurture its covert operations?” This intriguing centuries-old question is still an enormous mystery to most of us, but there are several fascinating sub-questions whose individual answers can aid in piecing together some of the constituent keys to constructing an answer to our important original question. Among those questions are,

  • What parts inside the brain are involved in allowing for thinking, learning and memory?
  • Does the brain change during life and during the process of learning or is it a permanently fixed/hard-wired creation?
  • What can we do in our schools (and homes) to enhance learning and what can we do to remain mentally alert and healthy as we age?

In years past, we would often engage in a lengthy and detailed discourse examining the issues of learning, knowledge acquisition and child development. During those conversations, we deliberately avoided even mentioning the human brain as the foremost contributor to these activities or as actually orchestrating every aspect of these events, although the role of the brain genuinely merited a centerpiece status.

However, the most recent advances in the fields of molecular biology, neuroanatomy, medicine, brain-imaging, genetics and the numerous branches of neuroscience emerging today, now permit us to take a closer look at the chemical, functional and structural facets of just how the brain actually does work. We are discovering the many neurophysiological correlates of cognitive functioning and the neural activities that regulate all components of human learning. The human brain, acclaimed as the universe’s most complex structure known by man, is gaining currency in these discussions and is now ascending to its rightful place as the focal point of all learning equations.

It has been said that the next great journey of discovery for humankind will not be in outer space, but in the inner space of the human brain. In order to grasp what is happening in the interior of that well-concealed “inner space” of our students (to say nothing of our enlightened self-interest), it is helpful to understand the answers to the following big

questions about the human brain:

What are the basic parts of the human brain and what do they do?

We have yet to discover any object on earth that is better organized, more adaptable or capable of performing at a higher creative level than the human brain. But, what are the parts of our brains and the unique characteristics that promote these impressive capabilities?

There are two major parts to the human nervous system — the peripheral nervous system and thecentral nervous system. The sensory receptors in the peripheral nervous system (PNS) receive information or stimulation from in the local environment and send it to the central nervous system (CNS), where we process the incoming information. The brain is part of the central nervous system, which is composed of the brain and the spinal column. Once a decision has been made by the brain, the “command post,” concerning precisely what to do with the incoming information, the brain transmits signals to the muscles, glands and other organs for the execution of its “final answer” or its immediate reaction.

In vertebrates, the brain is customarily divided into the forebrain, the midbrain and the hindbrain. However, the brain is also described as being composed of three basic interconnected anatomical components:

1. The brain stem, which is approximately the same size of your index finger, controls the vital processes such as heart rate, breathing, and digestion. It monitors most of our body’s sur vival mechanisms
2. The cerebellum, in the hindbrain, is a cauliflower-like structure in the posterior region of the brain situated just below and behind the cerebral cortex. The cerebellum is approximately 1/8 the size of the cerebral cortex and assists with tasks such as balance, muscle tone, movement and coordinating the body’s senses. It makes many of our automatic behaviors possible. Every time we get up in the morning, stand at a podium, or walk down the corridor, our cerebellum deserves the credit.

3. The cerebral cortex (cortex is the Greek term for “tree bark”) is home to all higher brain processes and will be the focus for most of this article.

The first two brain components, the brain stem and the cerebellum, regulate all of the body’s unconscious routines and are the intake sites for registering our outside experiences. Practice, to the brain, does not necessarily lead automatically to “perfect” performance. Repetition in the cerebral world contributes to the eventual hard-wiring of the brain and it, in due course, might lead to habitual responses or behaviors governed by a phenomenon called “automaticity” or automatic reactions that require only modest amounts of cerebral activity.

Most automatic behaviors are handled primarily in the cerebellum, not the cerebral cortex. Those neurons that fire together regularly will in time wire together permanently, in such a fashion that practice makes permanent, rather than perfect. Inefficient strategies will not guide one towards enhanced performance levels. A repetitive, albeit improper, execution of a target skill does not improve its quality, nor does it move one any closer to a performance approximating perfection than doing nothing at all. (In some cases, nothing would in reality be preferred – to avoid the development of “bad habits,” which are difficult to break). Regular incorrect efforts will indeed cement that skill, but in an imperfect neural configuration.

An error-filled page of a student’s work in mathematics doesn’t in any way suggest that his proficiency in mathematics has been elevated. Only rehearsals completed in the correct format of the target skill will result in positive or “perfect” changes.

The cerebral cortex, which has changed very little in human beings over the past 200,000 years, is divided into two corrugated hemispheres, which sit astride the central core of the brain. There are distinctive asymmetrical left and right hemispheres, each with its own specialized functions. Typically, the left hemisphere controls the right side of the body and the right hemisphere controls the opposite side of the body (referred to as “contralateral”) in vertebrates such as human beings.

Motor commands and responses in the bodies of invertebrates are controlled by the same side of the brain (right-to-right and left-to-left or “ipsilatreral”). Human brains show a clear dominance for contralateral input and command instructions, although small amounts of data are also processed by the cerebral hemisphere on the same side of the body.

The quicker-processing left hemisphere (1) produces and interprets language, (2) is responsible for numerical skills, and (3) is the home of our reasoning abilities. The left hemisphere is also considered to be the more analytical of the two sides of the brain. The slower-processing right hemisphere decodes and processes patterns, music, spatial relations, and takes in the “whole” or the Gestalt possible, along with adding the emotional content to language. Familiar faces are recognized by the “left brain,” while the right side processes unfamiliar or new faces. The right side is considered the more creative hemisphere and it also processes the novel aspects of new situations. Once the novelty wears off, the pertinent new information becomes the property of the left hemisphere. Perhaps later, it will be forwarded on to the cerebellum, the home of automatic responses.

Normal human brains are lopsided. The left hemisphere is generally larger and more active than the right. Whenever the two sides more closely approximate symmetry, the left hemisphere is usually somewhat underpowered. This neurophysiological downside is suspected as a leading cause in incidences of language disorders. In females, the left hemisphere is noticeably larger than the right. However, the male brain appears slightly more symmetrical, as the average male brain comes equipped with a larger right hemisphere than would be typically found in females. It is no coincidence that nearly 80% of the cases of developmental language delay, dyslexia, stuttering, and a host of other language-related problems involve boys rather than girls. No matter where one travels, it is not uncommon to find that 80% or more of the children enrolled in remedial reading classes in the elementary grades are boys. In middle and high schools, the figure climbs to 90% and above. More than three quarters of the men in America’s prisons have severe a language, reading, learning or hearing problems or some combination thereof. Over the course of the 12 years of formal education, a 1.7-year gap in language fluency will often separate boys from girls.

When viewing the brain, one of its unique features is the wrinkled nature of its two-millimeter thick surface. The wrinkles or folds permit the relatively fixed volume inside the human skull to house a fairly large amount of neo-cortical surface tissue. It represents nature’s solution to the challenge of fitting the large cortical surface inside a tiny skull. A newborn’s head is just small enough to squeeze through the birth canal, which is customarily 102-103% the size of the cervix (cephalopelvic disproportion or “CPD”), creating the great challenges during delivery without damaging the precious cargo packaged neatly inside the cranial vault. The activities surrounding a normal delivery constitute one of the world’s most impressive displays where geometry, physics, obstetrics and economics are all utilized to accomplish the same mission, while using principles from each of these disciplines simultaneously.

Only cats, dogs, monkeys, dolphins, and humans have evolved to the point where it is necessary that the brain must fold onto itself in order to fully developed. Rats have smooth unfolded brains, which is partially why their brains are ideal for the purpose of experimentation. If the human brain were unfolded and stretched out, its surface area would be approximately the size of a desktop (2.5 square feet or 2500 cm2). The interesting highly convoluted surface, with topographical crevices, mounds and folds is not at all unlike a wadded-up dinner napkin stuffed into a pants pocket. With the exception of cases in which the observable protrusions, nooks and crannies are evidence of disease, brain trauma (or research that is going quite poorly), the configurations are likely one of the following distinctive brain characteristics:

Gyri (“gyrus” in the singular) are the wrinkles or ridges, which are typically the brain’s most distinguishable feature.
Sulci (“sulcus” in the singular) are the shallow valleys reaching just beneath the surface of the brain, seen as folds in the cerebral cortex. The sulci become increasingly wider in the event of brain atrophy.
Fissures are the deep indented clefts on the brain’s surface. The medial longitudinal fissure separates the brain’s two large hemispheres. It appears just above the corpus callosum, which connects the two hemispheres of the cortex. Similar deep fissures also partition the brain into four lobes (the frontal, parietal, occipital and temporal lobes). When comparing the fissures found in just one individual’s brain, those fissures seen in the right hemisphere will not be identical to those on the left side of the same person’s brain and vice versa. There will be an even greater amount of variation in the location, size, and pattern of the gyri, fissures and sulci in the brains of two different individuals. The cerebral configurations found in the brain of Person “A” reflect the neurophysiological results of his genetic background and his brain’s on-going responses to his specific environment.

The cerebral cortex in the human brain is approximately as thick as an American dime and is composed of six layers of brain cells (see figure 1).


Figure 1 – The six layers of brain cells

Layers #1, 2, and 3 of the cerebral cortex are the “mental processing” layers of the brain.

  • Brain-imaging technologies have shown that the greatest amount of neural activity takes place primarily in the second and third layers, with only modest amounts of cortical activity found in layer #1, on the surface of the brain.
  • Together these three layers represent approximately 40% of the total thickness of all layers in the brain.

Layers #4, 5, and 6 are the “input/output processing” layers of the brain.

  • The 4th layer of the cortex receives incoming signals from the sensory systems found in the PNS
  • The 5th and 6th layers are the areas that govern the outgoing motor activities.

Collectively, these three layers account for over 60% of the cortical thickness in the human brain.

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