Historical Overview
The significant problems facing us today cannot
be
solved at the same level of thinking that we were at
when
we created them.—Albert Einstein
The human brain is the most complicated and adaptable single object residing in the known universe. Despite the brain’s complexity, however, scientists have been able to make progress in understanding it. Their findings have enabled educators to deploy more powerful pedagogies and construct a brain-considerate system of education. Developing a respectable knowledge base regarding “how the brain works” is necessary for boosting achievement and maximizing the potential of every student in our classrooms. All educators need to understand the inner workings of the human brain so that they can put the research findings from neuroscience to the most profitable classroom advantage.
In one manner or another, investigations into the mammalian brain from centuries past have contributed to our contemporary reservoir of knowledge. Five notions which set the stage for our current understanding of the brain will be covered in this module.
Early Evidence of Brain Investigations
In early civilizations throughout the world, most notably in South America, there is abundant evidence of brain investigations (Bishop, 1995). Skulls from these civilizations indicate frequent trepanation, a crude method of brain surgery. As early as 5,000 B.C., Pre-Inca and other early practitioners bored holes into the skulls of individuals suffering ailments that ranged from migraine headaches, epileptic seizures, and mental disorders to possession by evil spirits. Skulls have been uncovered that have several holes, indicating that large numbers of patients received multiple treatments for on-going mental health difficulties. Equally important, in several locations trepanized skulls have been unearthed with revealing signs of post-operative recoveries, indicating that patients survived well beyond the time of these surgical procedures. This high number of trepanized crania found worldwide points to early awareness of the human brain’s central role in orchestrating behavior, an understanding which pre-dates similar thinking in European civilizations.
Early Egyptians, in contrast, could attribute nothing of significance to the human brain. During their elaborate mummification process, they extracted the brain with gross indifference via the nostrils and disposed of it unceremoniously, even though they preserved the heart, liver, kidneys, and lungs for service in the afterlife. Interestingly, their medical texts do talk about the brain. An ancient Egyptian surgical papyrus from 3,000 B.C. records twenty-six cases of brain trauma along with corresponding procedures for treating specific injuries. Moreover, the term “brain” has been found on a surgical papyrus dating from 1,700 B.C.
The father of Western medicine, Hippocrates (460-379 B.C.), contended that the human brain was the principal organ responsible for intelligence. In contrast, Aristotle (384-322 B.C.) and the leading thinkers of his day advocated the cardiocentric position which supported the notion that the human heart was the seat of all cognitive abilities, as well as the human soul. The brain was relegated to more humble undertakings comparable to a radiator designed
exclusively to cool the hot blood circulated by the heart. The brain’s relationship to behavior and cognitive functioning was significantly and consistently overshadowed by a focus on the heart. Throughout the first millennium and a half, written records in the Western world mistakenly pointed to the heart as the center of human behavior, consciousness, and cognition. Our contemporary language still reflects vestiges of this perspective. Today, we refer to successfully memorized facts as information that we know “by heart.”
The church sanctioned the cardiocentric underpinnings of philosophy, medicine, and science. Moreover, the church made it clear that one’s longevity and his or her support for church positions intersected. Science, medicine, and education safely mirrored the church.
Electricity and the Brain
In 1791, Italian scientist Luigi Galvani demonstrated that electrical forces not only exist in the body, but that electricity also plays a dynamic role in the operation of nerves and muscles. Galvani’s experiments showed that it was possible to activate the motor nerves connected to a frog’s leg muscles by introducing a mild electrical current. He concluded, erroneously, that muscle movements were proof of electricity flowing between the nerves and the muscles. His research, however, took the emerging study of the electrochemical basis of neural activity and pointed it in the right direction. Galvani’s astonishing discoveries inspired Frankenstein, Mary Shelley’s 1818 novel. The novel’s popularity served as a testament to the torrent of public curiosity in scientific research that was unleashed by Galvani’s fascinating research findings.
In the early 1900s, teams of researchers, notably Adrian, Erianger, and Gasser (Finger, 2000) discovered electrical pulses traveling through brain cells. Today, it is common knowledge that motor and cognitive functions rely on a combined electro-chemical neural process. Neurons, the “network communicators” inside the brain, transmit messages to one another by sending electrical signals down the neuron’s elongated axon. The electrical signal triggers the release of neurotransmitters which carry chemical messages to adjoining neurons along a neural circuit.
Phrenology
Throughout the 19th and 20th centuries, a steadily growing list of investigations provided increasingly greater detail on how particular brain regions were responsible for producing specific skills, behaviors, and human faculties. The most reliable theories were born in the error-riddled pseudoscience of Phrenology.
Phrenology was the result of work by an Austrian medical student, Franz Joseph Gall, who identified twenty-seven personal traits, talents, and predilections. He selected a corresponding brain region for each trait. The fundamental premise of phrenology, the “brainchild” of Gall, was that the human mind was indeed like other muscles in the body, and that exercising any of the twenty-seven personality traits, skills or mental functions would produce a corresponding increase in the quantity of brain tissue in that brain area.
According to Gall’s theory, high levels of activity would eventually cause the brain tissue to swell just beneath the surface of the cranium, producing detectable bumps on the skull of an individual. These excessively used regions would ultimately alter the external contours of the cranium. Affluent members of society and prominent businessmen had their skulls measured and analyzed. Favorable phrenology results were illustrated on personal busts which they proudly displayed in homes and offices. The crowns of walking canes, designed to impress others, were similarly adorned with detailed reproductions of a phrenologist’s assessments.
The primary sources for Gall’s research were sculptors’ busts of highly accomplished individuals and the cadavers of criminals and the mentally insane. There was, however, nothing scientific about phrenology. Among the earliest clues rendering the very foundation of phrenology questionable was the fact that few “experts” ever reached the same scientific conclusions, generating growing and well-founded suspicions. Detractors, including French experimentalist Marie-Jean-Pierre Flourens, referred to phrenology as “Bumpology.”
Nevertheless, phrenology was wildly popular, widely accepted, and extremely profitable during the 1800s and the early 1900s, both in Europe and in the United States, despite its enormous methodological deficiencies, its arbitrary selection of primary characteristics, and its unscientific assumptions and conclusions. Few psychologically-based schemes have ever generated the level of attention or the revenues of phrenology during its heyday.
Although phrenology was completely incorrect with respect to its behavioral attributions, the theory serendipitously suggested that there were indeed structural, functional, and regional correlations in the human brain. The true legacy of Franz Joseph Gall and the theory of phrenology was setting the stage for more scientifically-based and dependable theories related to the localization of brain function.
The Localization of Function
Finger (2000) describes a series of experiments from the 19th and early 20th centuries which investigated functioning in mammalian brains. These experiments by Marie-Jean-Pierre Flourens, Hermann Munk, and John Hughlings Jackson ranged from examining which areas of the brain were responsible for coordinated voluntary movements to the specific effects of localized brain damage in the cerebrum, the spinal column, and the cerebellum.
In hundreds of well-documented experiments, Gustav Fritsch, Eduard von Hitzig, and David Ferrier selectively removed various parts of mammalian brains, producing focal lesions (precise regional brain damage) to study the responsibilities associated with particular areas of the cerebral cortex and the brain’s sub-cortical structures. Their investigations included applying an electrical stimulation to one side of the brain to produce a response on the opposite side of the body (contralateral motor cortex). This principle turned out to be true for all mammals including human beings.
The systematic investigations of Paul Broca, a young French neurologist who worked with institutionalized stroke victims, helped to locate the region of the cerebral cortex that plays a central role in language production. In 1861 when one of his patients died, the autopsy showed a lesion in the area of the brain (the third gyrus of the prefrontal cortex) known today as Broca’s area.
Broca’s research paved the way for subsequent research by a German neurologist, Carl Wernicke. While also working with institutionalized patients, Wernicke located the cortical region most responsible for understanding language. The location that converts speech sounds into meaningful language is known today as Wernicke’s area, positioned adjacent to the primary auditory cortex. Combined, Broca’s area and Wernicke’s area are considered to be the region of the brain where critical human language functions reside.
Surgeon Wilder Penfield is credited with making a significant contribution in charting the motor cortex. In the mid-20th century, Penfield startled the world by performing brain surgery on conscious patients who could report sensations or memories, depending on the precise areas of the brain that were being electrically stimulated by Penfield. Mapping the homunculus, which represents the sensory and motor cortices, was possible only through the daring surgical procedures first attempted by Penfield.
Until the latter half of the 20th century, most discoveries about the human brain came by way of research opportunities that were made available only through human tragedies.
Mass Action
Memory storage in the cerebral cortex mystified brain researchers including Karl Spenser Lashley, who probed into the localization of memory (Kandel, Schwartz, & Jessell, 2000). Using rats as his original subjects, Lashley researched the specific neural components of memory. Like Flourens, Fritsch, and his numerous predecessors, Lashley tested maze-running memories in rats while gradually eliminating selective portions of the rats’ cerebral cortices.
Lashley correctly theorized that there is no single place where all memories are stored in the brain. Instead, he found numerous components and connections that make specific, but simultaneous (parallel), contributions to the final memory product. Lashley authored a theory of “mass action” describing how the entire brain, as opposed to a particular module or neuronal component, is responsible for both memory and all other complex behaviors.
In the 20th century, the work of Lashley and others challenged the concept that a single area is exclusively responsible for a given cognitive function. Researchers, including Nobel prize-wining researcher Ramon y Cajal, began promoting the idea of a more holistic brain. Their theory described a rich variety of neurons arranged into functional networks that execute a specific action, although just one key brain region plays a central role in the final collective action. For example, the discrete elements of language are processed in the brain’s left hemisphere, while the right hemisphere provides meaning, humor and the Gestalt. These elements and functions, in tandem, make a process such as reading comprehension possible. Like a symphony orchestra, there are numerous contributors to the final single product—the observable manifestations of complex thinking and behavior.
Concluding Thoughts
The collective work of scientists pursuing answers to the question “How does the brain work?” has led us to the contemporary field of cognitive neuroscience, how the brain learns. We have moved from a cardiocentric view of learning to contemporary theories of learning based on sound, reproducible scientific findings. Although erroneous notions (phrenology, electricity, cardiocentrism, etc.) may have impeded the general public’s understanding of human behavior, early scientists were taking the first steps on the way to today’s insights into the learning brain. We now understand that the body-brain connection governs behavior, with the brain as the conductor of the cerebral symphony.
|
Incas |
Earliest evidence of brain surgery. |
|
Egyptians |
Viewed the brain as an insignificant organ. |
|
Hippocrates |
Thought the brain influenced behavior and intelligence. |
|
Aristotle |
Articulated a cardiocentric view which was later validated and embraced by the church. |
|
Galvani |
Demonstrated that electricity had a role in neural functioning. |
|
Phrenology |
A serendipitous pseudoscience that reduced the human brain to a limited number of “faculties” housed in precise regions. |
|
Localization of function |
Key regions of the brain are central to behavioral functioning. |
|
Mass action |
The entire brain, not just specific areas, is responsible for orchestrating all complex human behavior. |
References
Bishop, W. J. (1995). The early history of surgery. New York: Barnes & Noble.
Finger, S. (2000). Minds behind the brain: A history of the pioneers and their discoveries. UK: Oxford University Press.
Kandel, E. R., Schwartz, J. H., & Jessell, T. M. (2000). Principles of neural science. New York: McGraw-Hill.