Introduction
Although loss of productivity and human suffering represents a major force for
placing emphasis on brain studies, it is recognized that gains need to be made
in learning how the normal brain functions. In the last decade neuroscientists
have made major breakthroughs in their understanding of normal as well as abnormal
brain processes. Since teaching professionals are in a unique position to influence
the mental health potential of tomorrow's citizens, teachers must strive to
understand how our brains function in teaching, learning and dysfunction.
On a daily basis counselors and teachers observe students with a wide range of affective disorders. Mood dysfunctions, including depressions, feelings of hopelessness, and manias are found to affect 6% of today's student population. Additionally, substance abuse, anxiety disorders, attention deficits, eating disorders, and sleep disorders all contribute to our awareness that efforts need be made to seek support for research, training, understanding and prevention for the mental health issues in our schools.
The literature about the brain is growing very rapidly and teachers are challenged to keep pace with the information explosion about brain studies. For example, at the National Library of Medicine, nearly 100,000 publications in the archives contain the term "brain." This is more than double the number of such articles five years ago.
Neuroscience
Neuroscience is the term used to describe a large array of studies now underway
to discover how our brains function. Noted by many scientists as the last major
frontier in biology, the slow but steady investigation into how our brains work
is yielding a large number of new findings. Each facet of interest is promoting
its own field of study. Each is contributing to the growing fund of exciting
new information. The complexity of the brain is yielding to scientific analysis
and new pathways are being opened to the study of human behavior, learning,
memory and information processing.
This chapter will aid readers in understanding the importance of brain studies in contemporary terms. We will begin by examining the structure and function of our brains and the implications of recent research on teaching and learning.
Understanding a Popular
Educational Myth
The most deceptive educational myth of the last two decades is that of the left
brain/right brain dichotomy. Parents, teachers and administrators have been
heard making assertions about learners who are deficient in either "right"
or "left" brain capabilities. The myth has evolved that the left cerebral
hemisphere acts alone to control our logical, linear, rational thought, while
the right cerebral hemisphere controls metaphoric, intuitive, dreaming and holistic
thinking. Although there is evidence that the two hemispheres do present differences
in form and function, it is too simplistic to speak of right-brained or left-brained
students.
The brain's actual organization is as intriguing as the left brain/right brain myth. It may be useful for teachers to examine the depiction that neuroscientists now give regarding the brain's incredible complexity. It is time to realize that the brain has a top, bottom, front and back as well as a left and right side, all working together. As Jerre Levy (1985), a biopsychologist at the University of Chicago, said, "It is impossible to educate one hemisphere at a time." Indeed, the whole brain works synchronously to contribute to our uniqueness and well-being. Reading and other cognitive functions are especially complex behaviors requiring a large number of neurological activities in a number of specific locations in the brain. Let us examine contemporary ideas about how our brains develop and function, and how the complex processes work to allow humans to behave uniquely.
Anatomy
A brief mention of the four major components of our brain is necessary. The
brain stem (medulla) is the location of the connections made by the main nerves
for the five senses and other automatic processes. The cerebellum processes
information and governs learned and automatic motor responses such as balance,
walking, standing, typing and writing.
Thirdly, there is the complex interior central region, the "limbic" lobe of the brain. The word limbus means border. The limbic system is the border between our ancient brain that we share in common with all vertebrates and the higher conscious centers in the cerebrum. The limbic system is the anatomic substrate to our emotions. Fight/flight, fear, rage, aggression, joy, species preservation (sex), and self-preservation all have their loci of function here. Sexual maturity and our night/day rhythmicity are governed by the pineal gland, one subsystem of the limbic region. The pineal synthesizes one of the brain's neurochemicals, serotonin, an excitatory chemical that affects arousal during our waking hours and melatonin at night. We will have more to say about these neurochemical substances called neurotransmitters.
The limbic system is important to effective learning and knowing and is the center of the brain's controlling, organizing, or relay system. The thalamus and hypothalamus form the centers of a complex network that allows us to "switch" or focus our attention volitionally on scenes, ideas, visions, and other aspects of our physical environment, such as sound, touch and smell. It is also the system that relays affective feelings to the higher centers of the brain.
Fourth, there is the cerebrum, that portion of the brain that is central in the myth of the separate functioning of the right and left cerebral hemispheres. This is the center of humankind's highest neurological functioning: thinking, planning and remembering. The principal part is the thin covering, or cortex, a tissue about 3-6 mm thick and, if smoothed out with the wrinkles all lying flat, would form the cover of an average card table.
Visualizing the Cortex
and Hemisphere
Paul MacLean (1978) offers us a simple way to model the brain using our two
fists. He suggests that to visualize the cortex and the hemispheres, pretend
to put on a pair of grey gloves. Next, form two fists and join them at the fingernails.
The grey gloves form the cortex of the cerebral hemispheres represented by the
two closed fists. The major areas of the cortex have been known for many years.
With our gloved fist-brain as a model, we can represent the visual cortex with
our little fingers, our sensory cortex with the ring fingers, and the motor
cortex with the middle fingers, while the thumbs and forefingers represent the
highest center of the brain in humans, the association cortex, the area responsible
for conscious thought and action. The two halves are connected in the middle
as if our fingernails were joined with each corresponding nail. This structure
is called the corpus callosum. The left motor, visual and sensory cortex controls
the right side of our body. The right motor, visual and sensory cortex exerts
control over the left side of our body. We say that for most paired functions
the brain is contralateral in organization.
Attempts at mapping the various regions of the cortex to locate the functional areas of activity have been long-standing. The first marked advance in the mapping of brain functioning occurred in 1865, when Paul Broca (1865) correlated language loss with brain damage in the left temporal cortex. Thus, it was accepted that the left hemisphere was responsible for our language. Although this clinically proven fact is important, it failed to recognize the inter-relatedness of brain functioning. It has taken many subsequent generations of investigators to discount the notion that the left brain acts alone in controlling specific functions.
Cognitive Laterality
Different functional responses at sites in either hemisphere exist, but the
simple left/right breakdown is not supported by current evidence. Instead of
speaking about left brain/right brain, neuroscientists are now using the term "cognitive laterality" to describe these interrelated functional operations
(McManus & Bryden, 1991).
Motor cortex mapping has also yielded information about laterality. With our gloved fist model, recall that the two middle fingers represent the motor cortex. The area just above the middle fingernails in both hemispheres corresponds to the cortical region responsible for moving toes. As you proceed around the finger to the knuckle representing the band of the motor cortex, the regions coordinate successively our feet, ankle, calf, upper leg, torso, arms, fingers, and face.
If what we know about the pattern of the motor and visual cortex holds true with the frontal cortex -- that portion responsible for our focused conscious thought and memory -- then a new understanding of cognitive laterality emerges. This understanding suggests that the cerebral cortex is unique in each individual. We have already talked about patches of cortical cells of differing sizes, called modularities involved in information processing of all kinds (Gazzaniga, 1989). Gazzaniga says the cortex is densely multimodular.
A comparative review of the brains of representatives of the major vertebrate groups (Harvey, Krebs, 1990) shows that the functional parts are similar for all classes. As the reviewer progressively studies the gross anatomy of the brains from those of the cartilaginous fish to those of mammals, one easily notes that the amount of tissue devoted to the cerebrum increases. Although the mammalian brain contains all of the antecedent structures of the "lower" forms, the cerebrum is prominent in its size. The cerebrum in primates is the most complex, with that of man being the largest and most developed. The cortex is metabolically very active and requires 20% of all of the energy needed by the adult human. This is true while at rest, sleep, or actively engaged in problem-solving.
It is noteworthy that while the mass of the cerebrum is largest in humans, it is the cortex that is responsible for conscious thought and action. The cortex, sometimes called the grey matter, comes from the fact that outer layers of cells are more apt to selectively absorb differentiating stains for microscopic review and analysis than those from within the cerebrum.
The mass of tissue beneath and surrounding the six layers of cortical cells called neurons is known as "white" matter. The white matter is less dense than the grey matter and is composed of cells called "glia". The glial cells act as "attendants" to the neurons. They serve to provide the neurons with oxygen, metabolites, glucose, and amino acids -- the important chemical building blocks which form a class of neurotransmitters that allow neurons to communicate with each other. Likewise, the glial tissue serves to act as conduits to remove metabolic waste products including urea, water, and carbon dioxide from the cortical neurons. Glia also deposit the fat, myelin, on nerve surfaces and provide the brain with its own immune system.
An examination of the intact human brain shows the familiar wrinkled and folded appearance. The cracks are called fissures or sulci (singular sulcus) and the outward folds gyri (singular gyrus). The wrinkles and folds permit a larger surface area, hence more cortex.
Careful studies are underway to more precisely map the various regions and modularities of the cortex (Witelson 1990, Gittelman et al 1990). This process is difficult because the brain is secure inside the skull and because technology that allows an examination of the functional brain is still being developed. In animals, probes can be used to detect specific neuronal activity. In humans, positron emission tomography (Mazziota & Phelps 1985) and magnetic resonance imaging are being used to more precisely map the specific functional regions of the brain. Additionally, damaged brains can offer clues to the roles of specific areas. In fact, it was this approach that revealed to Paul Broca (1865) in the last century that human speech centers are normally found in the left temporal region. Studies of savants, too, provide neuroscientists with insight about specific functional regions.
Three sets of studies serve to illustrate the emerging information on brain mapping. First, the Nobel Prize winning work of Torsten Wiesel and David Hubel (1962) have mapped the visual cortex of the cat. They have identified specific modularities responsible for seeing vertical, horizontal, moving, and shape elements. Using techniques similar to those employed by Wiesel and Hubel (1962), Kass et al (1978) have mapped the motor cortex of the owl monkey responsible for finger movement. This approach employs an electrode which records neuron activity in patches of cells following vertical penetration of the probe from the white matter/grey matter boundary to the surface. Remarkably, the findings show that the owl monkey motor cortex anatomically parallels that of humans and that use with rewards will cause modularities responsible for specific movements to grow.
Positron Emission Tomography (PET) is another technique that allows researchers to measure metabolic activity in various sites in the brain. Inference holds that sites with greater metabolic activity are also those with greatest functional activity. Researchers such as Michael Phelps and John Mazziotta (1985) at UCLA have shown that PET techniques can reveal the complex patterns of functionality in the human cerebrum. These findings further corroborate the modularity idea and give us information about functional sites in the cortex.
In addition, Marian Diamond's (1985) work on the brain of a genius (A. Einstein) has shown that the percentage of glia cells and the amount of the neuronal branching is greater than non-genius controls. She has also concluded the same is true for the brains of rats raised in an enriched rat environment. What has emerged from past work and is being corroborated by present efforts suggests that the brain has numerous loci of cells responsible for very specific duties. Our understanding now holds that a single modularity or groups of modularities associate together to perform specific mental tasks (Fodor, 1983). It is further postulated that the size of a modular unit depends on the amount of external stimulation required of a given mental or motor task. For example, Merzenich et al (1978) trained an owl monkey to perform a specific task with the second finger for an hour daily for three months. The cortical modularity responsible for this task was mapped before and after the differential stimulation of the forefinger. After the training this area quadrupled in size. Conversely, it has been determined that if the finger responsible for the increased size of the modularity is removed, then the modularity responsible for this task will be taken over (cannibalized) by neighboring modularities. This plasticity of cortical function has profound implications for teachers.
It appears that increased stimulation can indeed improve performance by increasing the amount of cortex relegated to a specific mental task. This "use-it-or-lose-it" idea is intriguing when one realizes that there is but finite space in the cortex. Does this mean that in areas assigned to critical higher mental processing, overstimulation of one facet of the intellect might "take over" regions that could be utilized for some other mental process? Can this explain, in part, individual uniqueness?
The acceptance of the mental modularity idea is gaining favor. Although studies of motor and visual cortices in the lower primates and kittens are important, it is speculation about our own frontal or higher centers that are most intriguing (Gittleman & Prohovnik 1990). How many modularities might the average human possess? Are these similar or different from individual to individual? To what extent does culture affect modularities? Are gifted individuals different because of increased modularity size or because of uniquely distinct modularities? How are those individuals with learning disabilities affected? Will the modularity model apply in all cases?
What follows is an attempt to speculate on some individual modularities in the association (frontal) cortex. Association here refers to both mental activities that require inference or interpretation and multiple mental processes going on synchronously. First let's list some mental modularity problems that can be found in most psychology and special education texts (Obler & Fein 1988). The list below identifies what may be modularity insufficiencies:
Could complicated learning problems like autism or dyslexia also be modularity deficits or neuronal communication problems?
Even more intriguing to teachers than pathological issues are the often used modularities associated with social growth and learning specific curricular content. These, along with questions associated with the causes of giftedness and special talents, should be considered. An aspect of these ideas has been suggested by Harvard's Howard Gardner (1983) who speculates that there may be as many as eight "types" of intelligence. Individuals differ widely in their intellectual mix and not all of us possess the same mix. Although we have been discussing the biological substrate of abilities and inabilities, teachers have long known of individuals who are different through observing their students. Some abilities may be normally distributed among individuals. Memory is one such factor. Other special attributes may reside in only a few individuals and appear to be missing in the rest. Special art ability, music ability of several kinds (tonal memory, pitch), auditory or visual calculations, chess aptitude, and pattern recognition may represent modularities of this type.
As the mental modularity construct gains recognition, educators must realize the significance of its implications. Questions about neurological development, timing of the introduction of curricular elements, nutrition, enrichment emphasis, individual approaches to instruction, and the preparation of teachers all come to mind.
Will the emphasis on the neurological underpinnings to learning and behaving give teachers a new professionalism? It is bound to.
Development
Our picture of the brain isn't complete without discussing its growth and development.
Teachers are interested in individual uniqueness and it is at the neurological
level that most behavioral differences originate among individuals. First, understand
that the cortex with its various modularities and mental subsystems is responsible
for our focused thought and memory. It is composed of six layers of cells called
neurons. We are born with most of our cortical neurons. Few are added after
birth. Neurons that are lost or damaged do not regenerate (Epstein, 1978).
Since the brain only weighs approximately 355 grams at birth (about the weight of a can of soda) much growth must occur during our formative years - birth to sexual maturity. Indeed, the adult brain weighs 1,400 to 1,600 grams. If new neurons aren't added to the cortex, what explains the brain's growth in size?
Three things happen in the developing brain. First, the glia, or "white matter", multiply rapidly. Secondly, the brain increases in size by adding new blood transporting vessels. Finally, and most importantly to educators, is the slow transformation and growth that the neurons themselves undergo. This development and/or lack of development is probably the source of greatest variation in our individual learning styles and mental functioning (Epstein 1978).
It has been 15 years since Herman Epstein (1978) described for educators the stages of neurological growth in children and youth. These growth periods occur primarily between 3 to 10 months and from 2 to 4, 6 to 8, 10 to 12 or 13, and 14 to 16 or 17 years of age. Remarkably, these growth stages correlate with Piagetian theory.
What occurs during these developmental stages is an increase in the length and density of the tiny projections (dendrites) on each neuron. The term "dendrite" is from the Greek word dendron, meaning tree. This process, when viewed by early anatomists, was thought to resemble the growth of a forest of hardwood trees. The term "arborization" is given to this process. Although much remains to be learned about arborization, brain growth and development, it is almost certain that many of the differences among learners is directly tied to dendritic growth (Scheibel, 1990). In addition to an increase in density and length of the dendrites, the vast millions of neuronal fibers must become coated with an insulating fat called myelin. Myelinization of neuronal connections by their glial cell attendants is directly correlated with neurological development.
These developmental changes in the brain suggest an increasing complexity in the functioning brain. Current thought is that the visual and sensory cortexes develop first with gross motor, then fine motor actions, and finally with the higher learning frontal areas concluding the process.
The Biochemical Nature
of Thinking Memory Cognition
There are two forms of neurological communication. We have already briefly noted
neurotransmitters. The other factor is that neurons have the ability to produce
electrical current (collectively, enough to light an 11 watt light bulb). This
electrical current is produced through the rapid intracellular and extracellular
exchange of sodium and potassium ions.
The sodium/potassium ion exchange and the stimulation of neurotransmitters is too involved to discuss here. Simply stated, the electrical energy causes a chemical neurotransmitter (there are many different kinds) to be released from a neighboring neuron onto the receptor (boutons) of the next nerve.
One understands that if any of the internerve connections are improperly formed, communication between the various parts of the brain is impeded. Learning disability may result.
The reports on neurotransmitters (Skinner, 1991) is no less exciting than that of the brain itself. Many neurotransmitter deficits will be found to be closely associated with faulty cognition. Many substances, including heavy metal ions (lead, arsenic) and drugs may alter brain function by modifying the chemical signals that transmit and regulate the excitability between neurons. There is an enormous and growing literature supporting the effects of too much or too little of a specific neurotransmitter. Neuropsychologists now recognize that mental health is directly tied to normal levels of these vital compounds. One class of neurotransmitters associated with emotional states are the neuropeptides, made of dietary protein.
It would not be right to leave the matter of brain development and biochemical nature of thinking, memory and cognition without speaking forcefully for good nutrition. Brains are not constructed from a diet of adulterated food. Neither are neurotransmitters. Every day of our lives we must synthesize these chemicals from the food we eat. Need we speculate on the results of a diet insufficient or lacking the dietary requirements to make each of the vital neurotransmitters?
The potential that all of the findings that current brain research has for teachers is very exciting. The thought that teachers may someday have at their command procedures to mitigate learning disorders by prescription perhaps sounds alarming today, but this almost certainly will come to pass.
Educators have long searched for a substantive theoretical base to support their methodologies. The brain sciences have the potential to generate these new understandings.