the science teacher --- march 1982
Virginia R. Johnson ------- u-alaska - anchorage
( leyden's co-author of a '78 book: TEACHING SCIENCE GRADES 5-9 )
Brain growth and learning
The human brain develops from the back to the front, from the inside to the outside. The neocortex is composed of approximately six layers of neurons that develop at different times in different areas, and perform different functions. The two cerebral hemispheres are connected by a bun- dle of myelinated1 nerve fibers, called the corpus callosum. These fibers connect neurons in one hemisphere to similar neurons in the opposite hemisphere. The two hemispheres ultimately perform different, but complementary, functions. While each person has a particular time schedule for cognitive develop- ment, a similar pattern seems to prevail.
sensory motor (up to age 2),
preoperational (ages 2-7),
concrete operational (ages 7-11), and
formal operational (age 11 through adult).
after a lot of noise from about 1978-1982 - the idea of brain growth spurts was attacked as being "nice" but "we need lots of hard, physiological evidence that this really occurs like Epstein said it did -- and with the curriculum implications he warns about.
Sensory / Motor Development.
The sensory areas of the neocortex develop in three successive stages after birth. [i] Maturation of these areas depends on proper environmental and social stimulation. The first areas to develop (birth to three months) are the projection areas where incoming stimuli are processed. At this same time, growth occurs in the frontal lobes; the visual area of the corpus callosum; the spleenum, which is being myelinated; and spine to thalamus motor connections which are thickening. (See Figure 1.)
Preoperational.
The next growth period begins between two and four years of age, with the emergence of Piaget's preoperational period, in which the semiotic functions signal the beginning of language.[4j This is also the second of Epstein's growth spurt periods. Neurological growth occurs around the sensory projection area forming the specific association areas. These specific association areas store the incoming stimuli processed by the sensory projection area. The corpus callosum continues to myelinate past the sensorimotor cortex. In the left cerebral hemisphere, the arcuate fasciculus (a band of myelinated fibers) matures, joining Broca's speech production area in the frontal lobe to Wernicke's area in the temporal lobe where language comprehension takes place. The brain mechanisms for speech are now in place. Stimuli (auditory, tactile, and visual) can now be processed and stored. The language comprehension area is able to communicate rapidly with the speech production-motor area. The preoperational period is characterized by rapid development o~ motor skills and language; at this time, the child requires extensive social experience with spoken language. (See Figure 2.)
Concrete Operational.
The fourth growth spurt occurs at about seven years of age, as the Piagetian concrete operational period begins. The child can process and store sensory information, has developed language to reconstruct the environment symbolically, and he or she is now able to organize and perform operations involving one variable, while using concrete objects or materials. Neurologically, the corpus callosum has begun myelinating through the frontal lobes. The third sensory region, the nonspecific sensory association area, develops. These areas are interconnected, allowing sharing of sensory information between them.
If we present a child with learning tasks prior to the myelination of the areas needed to handle these tasks, we may be forcing the child, in its efforts to perform, to use less appropriate neural networks. By asking the learner to perform before the appropriate area is developed, we may be causing the failure and frustration seen in many children today.
After this seven-year growth period, the child is able to handle reversible operations addition, subtraction, multiplication, division, and phonics as long as concrete materials are involved. The concrete operational period requires stimulation which will involve the non-specific sensory as- sociation areas. The concrete experiences in elementary science are ideal for cognitive stimulation necessary to develop this growth spurt. This is perhaps why researchers found that the reading scores of elementary school children who were involved in hands-on science improved significantly. [5] Epstein has proposed that the development of each growth period depends largely on how well the previous growth period was developed. This observation closely parallels Piagetian theory. Can educators,then, afford not to provide hands-on science experience for their student.
While elementary educators talk about hands-on experiences for elementary mentary science and mathematics observation in schools shows, instead a predominance of work sheets and textbooks. Could the lack of proper stimulus and concrete experience [ a significant reason why less than 5 percent of the U.S. adult population can reason on the formal operation. level?
Formal Operational.
Epstein's 11-year growth spurt and Piaget's form. operational period occur concurrently ly, when there is increased develop ment in the nonspecific associated area, and myelination in the front lobe area is completed. Formal operational reasoning is now possible the concrete operational brain growl of the previous period has developed through proper stimulation and experiences. The child is now able to handle logic and abstract ideas. The 15-year growth spurt coincides wit the myelination of fibers in the rear associative areas. Because of frontal lobe development, the child now has conscious intent and can plan actions ahead of time, facilitating hypothetical reasoning and increased problem-solving abilities.
The role of the schools
The neurological areas of the brain that develop after birth necessitate the child's direct involvement-both active and social-with the environ- ment to stimulate maturation. Proper academic instruction, especially in science and mathematics, provides the ideal stimulation for brain growth during the concrete operational and formal operational periods. Unfortu- nately, many schools use written material, textbooks, and work sheets to teach abstract concepts. This practice is directly contrary to the active, sensory stimulation which neuroscience research indicates. When so many high school students are not functioning at the formal operational level necessary for secondary biology, chemistry, or physics, where can they find the experiences necessary to become formal reasoners? Should our secondary schools provide science courses in these subjects which are taught on the concrete level? This seems necessary if the majority of high school students are to take advanced science and mathe -matics courses and to develop formal reasoning in science and mathematics.
Attention and concentration
The human brain has mechanisms to filter incoming stimuli. The reticular formation, the limbic system, and the thalamus actively select the stimuli to which a person will attend. Evidence from attention studies on the human brain shows that the brain responds to novelty, to the unexpected, and to discrepant information. This could well account for the success of discrepant events used in science classrooms to stimulate student interest and problem-solving if abilities. Alternatively, when asked to perform the same task repeatedly, the brain "habituates," that is, repeats the operation automatically without consciously attending or te thinking about it. Hence, classroom drill and reinforced repetitive activities may actually be counterproductive to the learning of a concept. Teachers, therefore, should keep these activities to a minimum and use them only after the student's understanding of a concept is firmly established.
Hemispheric specialization
The third area of brain research - which shows great promise for edu- cational innovation is that of hemispheric specialization. The brain's neocortex is divided into two anatomically similar hemispheres, resem- bling a large soft walnut; these halves are joined by a bundle of connecting nerve fibers, the corpus callosum. Myelination of these fibers is complete at about age nine or ten, allowing the hemispheres to share information and its processing.
The two hemispheres develop differing, but complementary, abilities. (See Figure 4.)
activity
motor fibers in spine have reached thalamus
auditory background system is branching and growing
nerve cells multiplying thruout brain permits movement, touch
and pain, and general sensation
comments
permits hearing of environmental sounds, tones, body sounds
activity
period of neuron building is coming to an end
activity
rapid multiplying of glial cells thruout brain frontal lobe growth spurt
auditory background system keeps growing
visual area is growing rapidly
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permits building of basic
habits
activity
spine to thalamus motor
connections grow thicker
activity
glial cells have stopped
multiplying
auditory background system
completes growth
frontal lobes continue
growth spurt
corpus callosum finishes
myelinating in visual area
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assists in reach-grasp
activities
activity
visual area completes
growth spurt
comments
brain has adult visual
perception now
activity
frontal lobes finish growth
spurt
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frontal lobes won't begin
again until age 2
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frontal lobes won't begin
again until age 2
activity
growth of temporary neural
branches finally tapers off
comments
at this point, brain has
1.5 x the number needed
at maturity
activity
spine to thalamus motor
connections finish
myelination
comment
reach and grasp skills are
improving;
exploration activity begins
activity
slow. balanced brain growth:
no spurts
activity
auditory speech sounds
system begins growth spurt
comment
permits rapid acquisition
of language skills
activity
frontal lobes begin new
growth spurt
comment
assists in language
acquisition
activity
arnuate fasciculus
myelinates (links Broca's
area to WernickeÕs area)
comment
assists in language
acquisition
activity
corpus callosum is
myelinating past the
sensorimotor cortex
comment
improved sensorimotor
coordination
activity
rear associative network
begins to link up visual to
auditory to motor regions
comment
permits improved
coordination of actions
with what is seen and
heard
activity
spinal cord motor
connections reach frontal
lobes
comment
allows planning of
complicated, smoother
movements, greater skill
in copying movements
activity
pacemaker fibers from
reticular formation
network
activity
spurt in growth of skull middle of growth spurt;
best time to start math
and reading
comment
triggers a multi-region
spurt in brain growth
reach rear associative
activity
growth spurt slows down
activity
auditory speech sounds
system begins new 2 yr
growth spurt
activity
corpus callosum begins to
myelinate in frontal lobes
(2 year project)
comment
concrete reasoning skills
improve;
now can handle reversibility for phonics;
vocabulary building and foreign language learning skills are at peak
activity
spurt in brain and skull
growth
comment
permits brain to handle
logic and abstract ideas
6/6t/95