20TH CENTURY NEUROSCIENCE

There were remarkable breakthroughs in neuroscience during the later

part of the 20th century. Probing the brain with new imaging tools,

researchers explored the composition and function of specific regions

of the brain. A general understanding of the differences between the

right and left hemispheres emerged. Neuroscientists also concentrated

on the role of the rear, temporal (side) and frontal areas of the brain.

At the same time, educators investigated the implications of brain

discoveries for learning.

Parts of the Brain

• Left Hemisphere —Generally processes information as language and

math symbols; logical process orientation; predominant control of the

right side of the body

• Right Hemisphere —Generally processes information visually and

holistically; intuitive process orientation; predominant control of the

left side of the body

• Occipital/rear lobe —responsible for vision

• Temporal lobe (above and around the ears) —hearing, memory,

language

• Frontal lobe —planning, problem solving, abstract thinking

Today, researchers are moving well beyond 20th Century neuroscience,

which, for all of its breakthroughs, gave us a mechanical model of the brain,

a static perspective which assumes the whole to be the sum of the parts,

which may not be the case for the infinitely complex human brain.

In fact, despite regionalization, essential connections are well distributed and

completely integrated throughout the brain. Functions once thought to be

localized in a particular area are now known to engage many parts of the

brain in various lobes, hemispheres and more recently discovered areas

deep within the brain. New research frontiers include the exploration of

interaction between neurochemical transmitters and brain cells, as well as

the discovery of previously unknown functions of neurons and glials, the

most common cells in the brain.

Four Principles

Our emerging understanding of the brain centers around four

principles: Complexity, Connectivity, Plasticity and the

insights of Evolutionary Biology. In short:

The brain is complex.

The brain is connected.

The brain is plastic (or adaptable).

The brain evolved over the course of hundreds of thousands of

years, with tremendous consequences for the way we think and

learn.

Complexity A typical human brain has about 50 billion neurons. The total varies 20 to

40% from one brain to the next. Until 1998 it was believed that brain cells did not regenerate. We were thought to be born with a fixed number of neurons. Our brain cell count shrank as neurons died with age, or as a result of our life experience.

There is now irrefutable evidence that new neurons do grow within the brain, and they are integrated within existing networks.

“The brain contains more than a hundred billion neurons (also called

nerve cells or brain cells), which is about the number of stars in the

Milky Way Galaxy. It also has trillions of supportive cells called glia.

Each neuron is connected to other neurons by as many as forty

thousand individual connections (called synapses) between cells.

Multiply a hundred billion neurons times forty thousand synapses—

the brain has more connections then there are stars in the universe. A

piece of brain tissue the size of a grain of sand contains one hundred

thousand neurons and one billion synapses, all ‘talking’ to one

another.”

Besides neurons, glial cells are now understood to perform essential roles in thought and memory, a broader function than their earlier designation as cellular repair and maintenance organisms. The adult brain has between 50 and 100 billion glial cells.

The incomprehensible number of possible connections between neurons and glial cells hints at the complexity of the human brain.

If there were only 100 neurons in the brain, and if 50 were required to form a functional network, there would be 1.00891 x 10 29th possible combinations in a 50 cell connection. Imagine the possibilities when the number of neurons reaches tens of billions.

The brain has approximately one million miles of nerve fibers connecting these cells.

Connectivity In a simplified sense, new learning is the creation of a brain path that

did not previously exist. Maintaining a clear pathway for future passage facilitates memory. Traveling a well worn path toward a new destination represents the application of previous learning to a new situation.

Networks of connected neurons are the cellular pathways of the brain.

We now know that the synapses which connect neurons begin to form within 15 minutes of encountering new material in an intentional or explicit learning situation. The initial connection continues to develop for approximately one hour.

New information is stored temporarily by the thalamus, then dispatched to an appropriate area for processing. It gets fast tracked to the “fight or flight” amygdale if the information suggests danger. Next, the hippocampus is engaged for further evaluation and storage. Later, the frontal cortex may draw upon the information, often as part of a complex thinking operation.

Plasticity

The brain is remarkably adaptive. As Harvard Medical School

psychiatrist John Ratey points out, “Far from being hardwired

the brain is constantly being re-wired.” (John Ratey, Spark,

p.36) The brain’s ability to grow and change is known as

plasticity. In addition to creating new connections and even

developing larger physical capacities based on need, the brain

deletes old, unused connections. Two phases of aggressive

“pruning” occur during infancy and the teenage years.

Evolutionary Biology New Understanding, Old Brain

It may seem paradoxical to follow a discussion of brain

plasticity with reference to the limitations imposed by our

physical inheritance from evolutionary ancestors. According to

Yale University professor of psychology Paul Bloom, “There is a

considerable mismatch between the world in which our minds

evolved and our current existence. Our species has spent

almost all of its existence on the African savanna…the life of a

modern city dweller is an evolutionary novelty… (Paul Bloom,

New York Times Magazine, 4/19/09, p.11-12)

What does this image suggest?

Reflection Recent research suggests that once synaptic links begin to form,

the integrity of their connection is jeopardized if the brain

encounters additional stimuli in the form of more new learning. In

this regard, the brain works most efficiently if it forges one

connection at a time until a basic pathway has been established.

Here we have a powerful rationale for reflection. The initial

synaptic connections need time to solidify, and the reflective

pause allows them to do so, while other parts of the brain

evaluate the new learning and route information to the

appropriate place for storage and later retrieval.

“…(N)ew neural connections formed by the learning need

time to fix and strengthen themselves without competition

from additional novel stimuli. A simple walk around the block

can provide such gelling time.” (Pierce Howard, Owner’s

Guide to the Brain, p. 503)

Accordingly, you will now participate in a reflective

writing exercise to solidify the new information you

have just encountered about the brain and learning.

Reflective Writing

Reflective Writing Question:

Think about the four principles of brain based learning—complexity, connectivity, plasticity and evolution. What are the implications of these principles for learning in a traditional school setting? Independent or individual learning?