Why humans use more than 10% of the brain

By Sarah Choi

It appears to be common knowledge that humans only use part of the brain. The concept that the vast majority of the population only uses 10% of their mental capacity has been pervaded. It is even suggested that Einstein’s intellectual prowess was due to his ability to use more than 10% of his brain. However, this begs the question of the location of this hidden 90% of the brain, and whether humans can become more intelligent or more powerful by potentially unlocking all 100% of the brain.

While on this topic, the iceberg analogy may come to mind. Freud proposed that human consciousness is only the tip of the iceberg, and that unconscious thoughts, beliefs, and desires remain largely out of reach. He believed that the analysis of dreams was a path to a better understanding of the preconscious and unconscious, that then enables patients to deal with hidden issues that may have been adversely affecting their lives. In a similar way, the idea that most of the population can only access 10% of the brain, and that there is 90% of the brain still to be unlocked has been perpetuated. However, in relation to the biological brain, this is a misconception.

The brain is a tangible, solid organ of the body. It is connected to the whole body, sending and receiving signals from all around the body. The brain is made up of nerve cells, glial cells (with a diverse range of functions), and endothelial cells (for blood vessels). It is filled with these cells, and, as can now be seen from biopsies and brain imaging technologies, there is structurally no mysterious “bottom of the iceberg” in the brain. Additionally, scientists now know that every part of the brain has a certain function. All organs and organ systems in the body are functional, with a purpose (besides vestigial parts such as the appendix). Similarly, the space inside the cranium is not put to waste. 

Furthermore, the human body would not constantly be pumping nutrients into the brain, if it did not have this demand. Each neuron requires energy to maintain a resting membrane potential (more specifically, the sodium-potassium ATPases). Together with other processes, this amounts to a high energy requirement. In fact, an adult brain consumes 20% of the glucose burnt each day, and a child’s brain consumes 50% (Kuzawa and Blair, 2019). Compared to other animals and their brain sizes, this is an extremely high percentage. Having said this, it is not possible to use all 100% of the brain simultaneously. Due to the high energy requirements for propagating action potentials and transmitting signals to other neurons, the brain cannot withstand firing in all areas of the brain at once (Cytowic, 2014). So, while the brain is always active, only certain parts of the brain are in use at once.

On the other hand, many continue to live normally even with brain damage. This is due to neuroplasticity, the idea that other areas of the brain have the ability to take over the function of compromised areas. An example that has intrigued scientists for the past decade is of a man who lived with 90% of his brain damaged. He was diagnosed with hydrocephalus at an early age, and this condition continued until adulthood. This meant that the accumulation of cerebrospinal fluid pressed outward on his brain, over time reducing the brain to a thin layer of brain tissue beneath the cranium. Remarkably, this man remained conscious and led a normal life, albeit with a low IQ (Macdonald, 2016). Other cases have also pointed to the brain’s ability to work with certain areas damaged or removed. For example, the famous case of Phineas Gage points to the resilience and adaptability of the human brain and a woman who led an almost normal family life without a cerebellum (a large proportion of the brain’s neurons) (Stafford, 2014). Nevertheless, all of these cases have shown certain functions, however minor, to indeed be compromised following damage. Therefore, it seems that while the brain shows adaptability and plasticity, all 100% of the brain is still needed.

Whilst the concept that humans may innately have undiscovered power is encouraging and has inspired movies, the empirical evidence has shown that all 100% of the brain is indeed used. With increasing advancements, scientists have garnered physical evidence and knowledge of the structure and function of the nervous system suggesting that all regions of the brain have a purpose. Studies with numerous patients have further made it clear that humans use a lot more than merely part of the brain. So, perhaps, the idea of 10% is best left restricted to the area of psychoanalysis.

References:

Cytowic, R. E. (2014) What percentage of your brain do you use? – Richard E. | TED-Ed. Available at: https://ed.ted.com/lessons/what-percentage-of-your-brain-do-you-use-richard-e-cytowic (Accessed: 26 August 2020).

Kuzawa, C. W. and Blair, C. (2019) ‘A hypothesis linking the energy demand of the brain to obesity risk’, Proceedings of the National Academy of Sciences of the United States of America. National Academy of Sciences, 116(27), pp. 13266–13275. doi: 10.1073/pnas.1816908116.

Macdonald, F. (2016) Meet The Man Who Lives Normally With Damage to 90% of His Brain, Science Alert. Available at: https://www.sciencealert.com/a-man-who-lives-without-90-of-his-brain-is-challenging-our-understanding-of-consciousness (Accessed: 26 August 2020).

Stafford, T. (2014) Can you live a normal life with half a brain?, BBC Future. Available at: https://www.bbc.com/future/article/20141216-can-you-live-with-half-a-brain (Accessed: 26 August 2020).