Brandon Paton

The predominance of humans as a species is driven by our extraordinary capacity to learn. Through advances in science and technology, our understanding of the biological elements that facilitate human education has rapidly expanded. From birth to death, our brain is constantly changing itself, responding to new experiences and stimuli from the outside world. The human brain allows us to learn from, adapt to, and interact with the very environment that supports our existence.

Scientific research that supports our understanding of the brain stems from three primary sources. The first source of research comes from studying the anomalous brains of patients who have sustained a brain injury, stroke, or a debilitating condition that has affected specific regions of the brain. Documented changes in behavior, correlated to damage to certain regions of the brain, can facilitate novel insights into its functioning. Secondly, the advent of technologies such as positron emission tomography (PET) and magnetic resonance imaging (MRI) allows us to noninvasively scan and study the brains of healthy individuals. Thirdly, many functions and mechanisms of the brain are best understood under the vantage point of evolution.

An Overview of Basic Anatomy

Neurons are the basis of all functioning of the brain, including its ability to learn. Numbered in the billions, neurons are nerve cells that allow the brain to carry out its neurological functions. The neurons in our brain form comprehensive networks of neural pathways that facilitate our ability to play the piano, learn math, and to take a shower. These neural pathways are comprised of neurons that exchange information with each other by electrochemical signaling. Signaling takes place at the neuron’s synapses, where dendrites (the receiving end of a neuron) are in junction with axons from adjacent neurons (the transmitting end).

At birth, the brain contains the one-hundred billion neurons that are maintained through its entire lifespan. Neurons are post-mitotic cells, and thus are unable to divide. Humans’ cognitive triumph is not only attributed to the mere number of brain cells we acquire, but to the nearly infinite number of synapses by which neurons communicate. Each neuron can make anywhere from one-thousand to ten-thousand connections.

The brain also contains glial cells, which, contrary to neurons, are mitotic and reproduce in the brain. They provide support and protection to neurons, which they greatly outnumber. Glial cells produce an important substance called myelin, which forms a dielectric layer around the axons of neurons, called the myelin sheath. Myelin acts as an insulator, ensuring that nearby neurons are not inadvertently activated during active signaling, while greatly increasing their functional efficiency. Myelin increases electrical resistance across the cell membrane of axons while effectively decreasing capacitance.

Higher ratios of glial cells to neurons are correlated with increased cognitive functioning.  Fittingly, the cerebral cortex, a region responsible for cognitive processes, has the highest relative concentration of glial cells per neuron than anywhere else in the brain.

The myelination of neurons occurs on a gradual basis during the brain’s development. Various regions of the brain are myelinated according to genetic instruction following a designated timetable. The asynchronous myelination of neurons supports the notion that children’s brains become capable of learning different types of concepts and information at different times. But what exactly does the term “learning” encompass?

Learning and the Creation of Synapases

Learning is the brain’s creation and organization of synaptic connections in response to extrinsic circumstances. Additional connections, or synapses, that facilitate learning are created in two primary ways. The first method of synapse formation is by addition. The addition of new synapses is driven by learning experiences, and is the base of most forms of memory. The addition of neural synapses take place during the entire lifespan and is the primary method of synapse creation upon full development of the brain.

The second method is by synapse overproduction and loss, a process that occurs early in the development of the brain. When overproduction and loss takes place, the brain creates an excess number of synapses. At the peak of the overproduction, the brain begins to prune away the erroneous and unused connections. In the visual cortex, a person has more synapses at six months of age than during adulthood. What remains following the pruning cycle is a refined final form that constitutes the sensory and the cognitive basis for the later phases of development.

Overproduction and loss is a phenomenon first discovered by studying humans with visual abnormalities. If a patient’s eye is deprived of visual stimulation, due to a debilitating condition, during the overproduction and loss process in the visual cortex, the brain’s capacity to transmit visual data from the visual cortex to other parts of the brain is absent from the afflicted eye. Even if the eye can be surgically corrected, it will continue to be unable to perceive and transmit visual information, as the necessary synapses were pruned due to their former lack of stimulation. Nevertheless, the second, healthy eye in the same patient maintains normal function. Once the process of overproduction and loss has taken place in the visual cortex, the eyes can be deprived of stimulation for weeks and continue to function normally.

Similar to the way certain areas of the brain are myelinated at designated times, areas of the brain sustain the overproduction and loss process under a specific timetable. The peak of synapse production in the visual cortex occurs relatively quickly, allowing newborns to promptly utilize their eyesight. Conversely, this process in the frontal cortex, the region associated with higher cognitive functions, is greatly protracted. Synapse density in the frontal cortex increases before birth until five to six years of age, at which time the selection process begins and connections are pruned for a subsequent four to five years. The overproduction and loss of synapses is timed to take advantage of particular experiences, such that information from the environment effectively and efficiently organizes the brain.

Once overproduction and loss is complete in the frontal lobe, a framework for continued development by the addition and reorganization of synapses is in place. At this point in development, we are capable of learning with no developmental impediments.

Humans have a far superior ability to adapt to external stimuli than do animals, which rely heavily on innate and intrinsic knowledge. Animals have the advantage of being more “geared to go” at birth than humans. Human newborns are helpless, and require extensive parental care in order to survive and mature. This is a result of evolution increasing the size of the cranium and decreasing the size of the birth canal in women. This miss-proportion has caused most brain development to occur post-natal, when the size of the head and brain are not limited. In fact, the brain gains two thirds of its adult size after birth, with the large majority of synapses created out of the womb, allowing it to be shaped by both genetics and experience.

Processing of Information and Cortical Plasticity

On average, the brain processes forty-thousand bits of neuro-data per second. These bits comprise larger experiences or ideas that are meticulously broken down into individual, specific traits and characteristics, having been dissected into all of the specific parts that compose it. Each deconstructed piece of an idea is forwarded to a specialized subcortical structures that process that unique type of information. As this occurs, a particular array of neurons is simultaneously activated. If the experience or idea has occurred in the past, the brain will recognize the neural array, and will be familiar with the connections that comprise that experience. If, however, the brain is not familiar with the idea, it will not have a preexisting pathway of connections to instantly comprehend the concept. In this case, the brain attempts to use existing neural pathways that resemble the idea being processed; it uses a neural pathway of an idea with similar traits and characteristics that is embodied by the idea being processed. This process adapts similar, existing neural pathways to forge new ones, so that the idea can be more efficiently processed in the future.

As described above, the brain recognizes familiar concepts by existing pathways, and learns new concepts by relating them to similar, preexisting concepts. This method of learning in the brain has a significant downside: background knowledge is essential for learning and the development of new knowledge. It is nearly impossible to learn calculus without understanding the midlevel math that supports it. Similarly, hearing a conversation in an unfamiliar, foreign language proves completely incomprehensible due to the brain’s lack of experience with that language. The idiosyncrasies of individuals’ brains explain the varying levels of performance in a classroom of students. Each student has differing variety of background knowledge and experience available to relate all new knowledge to.

When the brain learns specific tasks, localized changes are made in areas of the brain that are appropriate to that task. For example, animals taught a maze have structural changes most significant in the visual area of cerebral cortex. If you teach an animal a maze with one eye blocked, only the part of the brain corresponding with the functioning eye will be affected. Learning complex motor skills causes alterations in the motor region of the cerebral cortex and in the cerebellum, a hindbrain structure that coordinates motor activity.

When the brain changes itself in response to stimulus, the functional organization is effected, which has been confirmed by electrophysiological recordings of nerve cell activities (National Academy Press, 2000). This is supported by the brain’s ability to transform the structure and function of certain areas of the brain, called cortical plasticity. The quality of information to which one is exposed and the amount of information one acquires during life is reflected by the structure of the brain and its neural pathways.

Cortical plasticity plays a role in increasing the efficiency of the brain. The frequency that particular neural pathways are activated correlate with the power and efficiency of those pathways, as well as the efficiency of the entire brain itself. This has been shown in experiments with animals being raised in complex environments compared to the same species raised in simple cages. Animals in complex environments, which encourage a higher degree of neural activity, show a larger number of capillaries per neuron than their caged counterparts. This indicates a greater blood flow through the brain. Experience, in this case, increases the overall quality of the functioning of the brain.

Another variable that is influence by the environment is the amount of astrocyte cells in the brain, a type of glial cell. Astrocytes function to support neurons by providing nutrients and removing wastes in the brain. Higher amounts of astrocytes have been found in animals that live in complex environments compared to caged animals, also correlating with the number of capillaries.

Adaptations to Stimuli

An experiment with rats has shown differences in the weight and thickness of the cerebral cortex between normal rats and rats placed in large cages enriched by the presence of objects that encourage exploration and other rats to interact with. The rats in the latter group exhibit better problem solving skills and higher cognitive function. What is interesting to consider is that rats placed in enriched environments with no interaction with other rats did not show the same benefit as rats living in enriched environments with other rats. The structure of the cerebral cortex was altered by exposure to the opportunity for learning, but only when coupled with the social factor of living with other rats. This study’s implication on human learning environments are still debatable.

Considering the previous example, we may wonder if the changes in the brain occur in response to actual learning, or merely an increase in the aggregate levels of neural activity. Learning, as well as acting out common everyday tasks, activates the brain. Before considering the research on this topic, it is plausible that the brain acts similarly to how muscle does, that it “grows” when you “exercise” it, regardless of the variance between the exercises. An experiment with rats suggests the contrary. Within an experiment, four groups of rats were established. The first were taught to traverse an obstacle course. The second ran on a treadmill everyday for fixed length of time. The third group lived in cages with a running wheel that they could voluntarily use. The fourth group sustained no exercise at all, acting as a control group.

The results of the experiment showed that the groups who exercised both voluntarily and involuntarily (groups two and three) had a higher density of blood vessels in the brain than the physically inactive groups, those that traversed the obstacle course and that were allowed no exercise (groups one and four). However, the group that was challenged with the obstacle course developed more synapses per neuron than the other three groups. This demonstrates that learning adds synapses, while repeatedly activating the same neural pathways (i.e. standard exercise) does not. In other words, different types of experiences condition the brain in different ways. Synapse formation and blood vessel formation (vascularization) are two important forms of brain adaptions, but are driven by different behavioral events and physiological mechanisms.

The Role of Memory

Traditional learning involves the ability to memorize and recall specific pieces of information, concepts, and ideas. Research has shown that memory is not a unitary construct, and that there is no specific area of the brain that is solely responsible for it. Areas involved in storing certain memories are influenced by the type of memory being stored. For example, declarative memory, memory of facts or events, occurs in brain systems involving the hippocampus. Procedural, or non-declarative memory, such as high level skills and other cognitive operations, occur in brain systems involving the neostriatum.

The way in which memory is formed in the brain contributes to the durability (or fragility) of the memory. For example, if asked to memorize a sequence of objects, most people would perform better if presented with pictures of the objects rather than their names printed on pieces of paper. This shows a superiority effect for pictures, due to the higher level of neural activity involved in processing the picture compared to the text. However, certain brains may be more adept to memorize and record written language as compared to pictures. These factors depend on the “wiring” of the brain affected by a host of intrinsic and extrinsic variables.

The brain learns and operates best when presented with patterns rather than facts. This is demonstrated by the cognitive difference between expert and novice chess players who are asked to recall the placement of pieces on a chessboard. When the pieces are placed randomly on the board in positions inconsistent to the game of chess, the expert and novice demonstrate a nearly equal ability to recall piece placement. However, when asked to recall a layout of pieces that are in positions that might occur during a real game of chess, the expert will have an easier time recalling the exact placement in consequence to his extensive familiarity and experience with possible board configurations.

When the brain observes a series of random events, it reorders them into a sequence that can be stored in an efficient manner that can be recalled in the future. The mind uses inferences to relate events in an act of efficiency and cognitive economy. The brain’s use of inferences is demonstrated in individuals who, over time, begin to believe known fallacies as truths. For example, it would not be too hard to convince a kid that they heard Santa’s footsteps on Christmas Eve if you consistently insisted that they did. In time, the child would retell the experience of hearing footsteps with vivid detail. By the use of brain imaging technology, we know that the recollection of false memories, such as in this example, activates the same array of neural pathways as actual memories.

The Function of Mirror Neurons

Another function of learning involves mirror neurons, which were first discovered by Giacomo Rizzolatti of the University of Parma in Italy. In many cases, when a student observes a teacher, mirror neurons are working in an observation and execution matching system, a form of imitation learning. Mirror neurons are located in the ventral premotor area of the frontal lobes of the brain, an area that is part of the larger premotor cortex whose function is linked to planning and the initiation of movement. Experiments have shown that when a monkey observes another monkey perform an action such as cracking a nut, the same array of neural pathways are activated in the observing monkey as are activated in the monkey performing the action. From this stems the ability of the brain to imitate and predict the actions of others. Consequently, people with non-functioning mirror neurons lack the understanding or empathy for other people, and are often withdrawn both socially and emotionally, two characteristics of autism.

Implications

The sporadic yet universal timetable of brain development, coupled with the idiosyncratic extrinsic circumstances that influence brain development, reveal to us that certain people are capable to learning different types of information at certain times. This demonstrates a weakness in the accepted methods of mass education. While having a class of students read a passage from the same story, the meaning of the passage is not conveyed by the story, but evoked by the individual. Activating the appropriate neural pathways for reading and understanding a given passage requires a preexisting corresponding schema and the background knowledge to foster the neural connections necessary to extract meaning from a passage.

Understanding the human brain is the highest level of self-understanding that can be derived from science, and we are well on our way. Nevertheless, there is a lot more to learn about the brain, our species, and the world in whole.  As we develop a greater understanding of ourselves, considering the possible implications of our scientific understandings are equally as important as the science itself.

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