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The human brain is a marvelous thing. It helps us learn and adapt. Central to these abilities is neuroplasticity, which allows our human brain to reorganize itself as necessary—even after traumatic brain injuries (TBIs).
- A neuron is a nerve cell of the brain capable of conducting electricity; these are the basis of our ability to learn and to function.
- Neurons have four parts, which include the soma (cell body), the dendrites (for incoming signals), the axon (for outgoing signals) and the axon terminals (at the end of each axon; release neurotransmitters).
- Neurons have one axon.
- Neurons can have thousands of dendrites.
- There are three categories of neurons (sensory, motor, and interneurons) but possibly as many as 10,000 types, each with a specific functionality.
- In the brain, a synapse is the small gap between two neurons, which allows for communication between neurons via chemical neurotransmitters. Functionally, synapses can be considered neuronal connections.
- Glial cells (collectively called glia) are the support cells for neurons.
Some Brain Facts
- Three pounds (between 1.3-1.4 kilograms) is the average weight of the adult human brain.
- One pound: the weight of the human brain at birth.
- Thirty thousand: the number of neurons that can fit on the head of a pin.
- Fifty to one hundred thousand: the number of other neurons to which a neuron might connect.
- Eighty-six billion is the best scientifically-determined estimate of the number of neurons in the human brain, though past references claim 100 billion neurons.
- On the basis of 86 billion neurons, there are potentially 0.86 quadrillion neural connections.
- According to one neurologist, the living human brain has the texture of soft tofu.
- Eighty percent is the amount of space in the cranium of an adult skull that the brain takes up.
- Five thousand years ago, humans had larger brains, at least for people descended from humans living in Europe, China, South Africa and Australia. Since then, the human brain has shrunk nine cubic inches (150 cubic centimetres)—or about 10 percent.
- Brain size does not correlate with intelligence.
- Two percent of body mass is taken up by the adult brain.
- Twenty percent of oxygen in blood is used by the human brain.
- Twenty to twenty-five percent of glucose sugar is used by the human brain.
- Neurons make up 10 percent of brain cells.
- Ninety percent of brain cells are “glia” (meaning “glue” in Greek).
- BBB (blood-brain barrier) protects the brain from large molecules getting through, while allowing blood and oxygen in.
- Neurons and glia form in the second trimester of a human fetus’ development.
- Teen brains are not fully formed, particularly the parts of the brain responsible for judgement, decision-making and multi-tasking.
- New neural connections are created throughout our lives.
- The human brain has rewired evolutionarily and rewires during our lifetimes.
- There are brain differences in the way men and women feel pain.
- A 2005 study indicated “in 78 percent of gender differences reported in other studies,” gender was not significant in affecting the behavior.
- A January 2010 study of nearly 500,000 boys and girls from 69 countries indicated “no overall gap in math ability”—something that has been said to be gender-based.
Brain Injuries Amongst Americans
Traumatic Brain Injury (TBI) is more common than you might think. Here are some facts collected from the Centers for Disease Control and Prevention (CDC) and other sources:
- Roughly $76.5 billion was the economic cost of TBI (medical and indirect costs, including lost productivity) in the USA in 2010.
- Ninety percent of that cost (approximately $68.85 billion) is due to fatal TBIs and TBIs requiring hospitalization.
- Two types of severe TBI: Closed (movement of brain within the skull) and penetrating (injury caused by foreign object in skull).
- TBIs can lead to various short- or long-term issues that affect cognitive functioning, motor functioning, sensation, and emotion.
- According to a 2006 CDC report covering 2002-2006, over 1.7 million Americans have a TBI yearly.
- Of these, 52,000 die; 275,000 are hospitalized; and 1.365 million are treated in emergency rooms and released.
- Approximately 1.372 million, or 80.7 percent of people who experienced TBI incidents made emergency department visits.
- Approximately 277,100, or 16.3 percent of people had to be hospitalized.
- The remaining 3 percent died.
- Nearly 0.5 million (473,947) emergency visits for TBI are made yearly by children 0-14 years old.
- Male children 0-4 years old have the highest rate of emergency room visits for TBI.
- A separate figure suggests at least 1.6-3.8 million sports-related TBI incidents occur yearly in the USA.
- There are likely additional Americans with TBI who do not seek treatment.
- TBI has four main causes, and other minor causes:
- Falling—35.2 percent (The rate is 50 percent amongst children 0-14, and 61 percent amongst adults 65+)
- Motor vehicle traffic crashes—17.3 percent
- Being struck by/against objects—16.5 percent
- Assaults—10 percent
- Unknown or other causes, including sports injuries—21 percent
- Men are 1.5 times more susceptible to TBI than women.
- Three age groups at risk: 0-4 year olds, 16-19 year olds, and people 65+ are the most susceptible to sustaining a TBI.
- Adults aged 75+ have the highest rate for death or hospitalization after TBI.
- Statistically, African Americans have the highest risk of death from TBI.
- Nearly one third (30.5 percent) of all injury-related deaths in the U.S. have TBI as a contributing factor.
- Seventy-five percent of yearly TBI incidents are mild forms that include concussions.
- Concussions are often considered to be mild brain injuries as they are usually not life-threatening.
- People with moderate head injuries are about 2.3 times more at risk for Alzheimer’s disease than the average person without TBI. For people with severe head injuries, the risk is about 4.5 times normal.
- Active military personnel acquire TBI mostly through blasts, but people in certain military roles (for example, paratroopers) are at increased risk.
- Ten to twenty percent of Iraq War vets (150,000-300,000 personnel) have some level of TBI.
Neuroplasticity: How Our Brains Rewire and Adapt
Neuroplasticity allows our brains to adapt throughout life under normal conditions, but is particularly important after brain injury from stroke, accidents and other causes.
- Three—the number of stages at which neuroplasticity occurs.
- Stage 1: Fetal phase until adulthood, when the brain grows and organizes.
- Stage 2: Throughout adulthood, for memory and learning.
- Stage 3: After brain injury, to regain lost functionality or to leverage what is left.
- Plasticity allows for specific body or brain functionality as represented in the brain to move to a different region of the brain, if and when necessary.
- For example, after a stroke, body functions such as limb use can be recovered from paralysis through new connections formed between intact neurons. This process requires stimulation through physical activity.
- New neurons can be formed; they do not stop being created at a particular age, despite previous beliefs.
- Neurons can form new inter-connections.
- Synapse structure can change.
- The areas of the brain that represent expertise in some skill or knowledge will grow, usually in thickness.
- According a 2006 study, the hippocampus of London taxi drivers was, on average, larger than that of London bus drivers. This is due to the hippocampus being the part of the brain dealing with complex spatial information for navigation—something taxi drivers are more likely to require, whereas bus drivers have predetermined routes.
- Similarly, a 2004 study showed that bilingual people have a larger left inferior parietal cortex than monolingual people.
- Musicians who practice at least one hour per day, according to a 2003 study, have a higher amount of grey matter (cortex) than amateur musicians, who in turn have more grey matter than non-musicians. Music skills are represented by multiple areas of the brain: motor regions, anterior superior parietal areas, and inferior temporal areas.
- German medical students researched in a 2006 study showed learning-induced changes in two parts of their brains (parietal cortex and posterior hippocampus) three months after studying for exams—compared to students who were not studying for exams.
Yoga and Meditation: Positive Effects on the Brain
Studies on the positive effects of yoga and meditation suggest that these practices can play their part in aiding neuroplasticity, especially after brain injuries.
- Research on meditation indicates that the practice can change the structure, as well as the function of the brain in a positive way.
- Meditation before student exams can increase performance scores.
- Practicing yoga can increase GABA (gamma-Aminobutyric acid) levels in the brain, which can alleviate depression and anxiety.
- Yoga practice can also increase alpha waves in the brain.
New Research on Einstein’s Brain
You’ve probably already heard the story of noted physicist Albert Einstein’s brain being preserved in mason jars, and that his brain was an average-sized brain. His brain’s weight upon his death was actually lower than the average adult brain weight of three pounds, but a 2013 study found something different about it that could account for his genius.
- The weight of Einstein’s brain upon his death was 2.71 pounds.
- In a 2013 study, however, it was determined that Einstein’s brain had a larger prefrontal cortex.
- Other parts of his left hemisphere were also larger than average.
- Einstein’s brain was compared against the brains of two groups: 15 right-handed men of 70-80 years of age (races unknown), and 52 right-handed white men of 24-30 years of age.
- Einstein was right-handed and died at 76.
- His brain weighed 1230 grams, similar to the mean brain weight of older study participants and less than that of the younger participants.
- His corpus callosum was “significantly larger” than those of the older participants and “slightly smaller” than those of the younger participants.
- Einstein’s callosum was thicker than those of both the older and younger participants in different regions, which supports the fact that he had “exceptional cognitive abilities.”
- The suggestion is that his brain’s hemispheres had greater interconnections than those of all participants, which is supportive of the fact that he had exceptional abilities when it came to spatial imagery and mathematics as well.
None of this can be considered conclusive without a comparison to other geniuses, particularly in the area of mathematics, but it does suggest that learning can change the structure of the human brain.
Information for this article was collected from the following pages and websites:
Infographic and screen reader information courtesy of TopCounselingSchools.org.
For more information on the brain’s neuroplasticity, check out our past articles BUDDHA’S BRAIN: Interview with Dr. Rick Hanson on the science and spirituality of the brain and REWIRING THE BRAIN: Mindfulness meditation training changes brain structure in 8 weeks>>