The Brain: Facts and Figures
Before getting into the some facts about our brains, a quick bit of terminology as light introduction:
- A neuron is a nerve cell of the brain capable of conduct electricity, and which are the basis of our ability to learn, to function.
- Neurons have 4 parts, which include soma (cell body), dendrites (for incoming signals), axon(for outgoing signals) and axon terminals (at the end of an axon; releases neurotransmitter).
- Neurons have one axon.
- Neurons can have thousands of dendrites.
- There are three categories of neurons (sensory, motor, 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, and which allows for the 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
Here are some general human brain facts and figures, before we get into the specifics of neuroplasticity.
- 3 pounds (between 1.3-1.4 Kg) is the average weight of the adult human brain.
- 1 pound — the weight of the human brain at birth.
- 30K — the number of neurons that can fit on the head of a pin.
- 5-10K — the number of other neurons to which a neuron might connect.
- 86 billion is the best scientifically-determined estimate of the number of neurons in the human brain, though past references claim 100B neurons.
- On the basis of 86B neurons, are a potential 0.86 quadrillion neural connections.
- According to one neurologist, the living human brain has the texture of soft tofu.
- 80% is how much space in the cranium of adult skulls that the brain takes up.
- 5,000 years ago, humans had larger brain, at least for people descended from humans living in at least Europe, China, South Africa and Australia. Since then, the human brain has shrunk 9 cubic inches (150 cc) — or about 10%.
- Brain size does not correlate to intelligence.
- 2% of body mass is taken up by the adult brain.
- 20% of oxygen in blood is used by the human brain.
- 20-25% of glucose sugar is used by the human brain.
- Neurons make up 10% of brain cells.
- 90% 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.
- Neurons and glia form in the 2nd trimester of a human fetus’ development.
- Teen brains are not fully formed, particularly for 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 fell pain.
- 2005 study indicated “in 78% of gender differences reported in other studies,” gender was not significant in affecting the behavior.
- A Jan 2010 study of nearly 500K boys and girls from about 70 (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 CDC and other sources:
- Roughly $76.5B was the economic cost of TBI (medical and indirect costs including lost productivity) in the USA in 2010.
- 90% of that cost (~68.85B) is due to fatal TBIs and TBIs requiring hospitalization.
- 2 types of severe TBI (Traumatic Brain Injury): 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 function, motor function, sensation, and emotion.
- According to a 2006 CDC report covering 2002-2006, over 1.7M Americans have a TBI yearly
- Of these, 52K die
- 275K are hospitalized
- 1.365M are treated in emergency rooms and released
- 80.7% (~1.372M) of people having TBI incidents made emergency department visits.
- 16.3% (~277.1K) of people had to be hospitalized.
- The remaining 3% died.
- Nearly 0.5M (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 1.6-3.8M sports-related TBI incidents yearly in the U.S.
- There are likely additional Americans with TBI who do not seek treatment.
- TBI has four main causes, and other minor causes:
- 35.2% — Falling. (The rate is 50% amongst children 0-14, and 61% amongst adults 65+)
- 17.3% — Motor vehicle traffic crashes
- 16.5% — Struck by/against events
- 10% — Assaults
- 21% — Unknown or other causes, including sports injuries.
- Men are 1.5 times more susceptible to TBI than women
- 3 age groups at risk: 0-4 year olds, 16-19 year olds, and people 65are the most susceptible to sustaining a TBI.
- Adults 75+ years old have the highest rate for death or hospitalization after TBI.
- Statistically, African Americans are at most risk for death from TBI.
- Nearly 1/3 (30.5%) of all injury-related deaths in the U.S. have TBI as a contributing factor.
- 75% of yearly TBI incidents are mild forms that include concussions.
- Concussions are often considered to be a mild brain injury as they are usually not life-threatening.
- People with moderate head injury are at about 2.3 times more risk for Alzheimer’s disease than the average person without TBI. For people with severe heady injury, the risk is about 4.5 times normal.
- Active military personnel acquire TBI mostly through blasts, but people in certain military roles (e.g., paratrooper) are at increased risk.
- 10-20% of Iraq War vets (150-300K personnel) have some level of TBI.
Neuroplasticity: How Our Brain Rewires and Adapts
Neuroplasticity allows our brain to adapt throughout life under normal conditions, but is particularly important after brain injury from stroke, accidents and other causes.
- 3 — the number of stages at which Neuroplasticity occurs.
- Stage 1: Fetal phase through until adulthood, when the brain grows and organizes.
- Stage 2: Through adulthood, for memory and learning.
- Stage 3: After brain injury, to regain lost functionality or 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 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 higher gray matter (cortex) than amateur musicians, who in turn have more gray matter than non-musicians. Music skills are represented by multiple areas of the brain: motor regions, anterior superior parietal areas, inferior temporal areas.
- German medical students researched in a 2006 study showed in learning-induced changes in two parts of their brains (parietal cortex, posterior hippocampus) 3 months after studying for exams — compared to students not studying for exams.
Yoga and Meditation: Positive Effects on the Brain
Studies on the positive effects of yoga and meditation suggests these practices could play their part in aiding neuroplasticity, especially after brain injuries. While the data is too extensive to include here, here are some takeaways.
- Research on meditation indicates that the practice can change the structure as well as 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 average-sized brain. His brain weight upon death was actually smaller than the average adult weight of 3 pounds, but a 2013 study found something different about him that could account for his genius.
- 2.71 pounds — the weight of Einstein’s brain upon death.
- 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.
- The comparison of Einstein’s brain was against two groups: 15 right-handed men of 70-80 years in age of unknown race, and 52 right-handed white men of 24-30 years in age.
- Einstein was right-handed and died at 76.
- His brain weighed 1230 grams, similar to the mean weight of older study participants and less than the younger participants.
- His corpus callosum was “significantly larger” than the older participants and “slightly smaller” than younger participants.
- Einstein’s callosum was thicker than 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 hemispheres had greater interconnections than all participants, which is supportive of his abilities in 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 web sites: