I saw a movie yesterday called Lucy. In this movie, a girl called Lucy absorbs a large amount of CPH4, and her brain capacity slowly increases.
So that brings me to my question which is :
Do we humans use 100% of our cerebral capacity or do we just use 15%?
The idea that we only use 10% of our brain capacity is a myth. There is a great article at wired.com that discusses the myth and it's history.
There is really no reason to evolve an entire brain of which only 10% is used. One great point that they make is that minor brain damage can cause devastating effects, not what you would expect if you had 90% spare capacity waiting around.
The entire brain is rarely firing all at once, and it is hard to average how much is being used because it changes with activity.
There is definite truth in the notion that we do not use the full capacity of our cortex. It is generally accepted that there is a reserve present in the brain that can act as a backup for cerebral damage. Brain reserve can be defined in terms of the amount of damage that can be sustained before reaching a threshold for clinical expression (Stern, 2002).
A notable example is the removal of nearly half of the cortex (referred to as a hemispherectomy) in children with intractable epilepsy. Although behavioral changes may occur and motor skills may become compromised (Van Empelen et al., 2004), these children generally recover remarkably well and overall intellectual performance may in fact improve as compared to before surgery. (Note, however, that the quality of life and brain function of these patients was severely compromised by their medical condition) (Pulsifier et al., 2004). Another example where the brain is shown to have a reserve is the fact that cognitively normal elders sometimes are diagnosed with advanced Alzheimer’s disease pathology in their brains at death (Stern, 2002). In other words, while their cortex was severely damaged by Alzheimer's, they showed no clinical signs of cognitive deficits.
In all, the brain has a remarkable amount of reserve, which may be interpreted as an incomplete use of total brain capacity.
While this reserve is critical for brain plasticity in response to injury and aging, it is questionable whether it is available to enhance cognition as depicted in the movie.
References
- Pulsifier et al, Epilepsia (2004); 45(3):243-45
- Stern, J International Neuropsychol Soc (2002); 8: 448–60
- Van Empelen, Brain (2004); 127: 2071–79
Note
The linked wire article in the accepted answer is popular science and I wouldn't base a conclusion on a '60-second-all-you-need-to-know' pseudo-scientific web link.
There is definite truth in the notion that we do not use the full capacity of our cortex. I think this is is not a meaningful statement. For me the problem here is that comparing the brain to a hard disk storage is very problematic. What exactly is capacity of my brain? The number of bits of information can I store before it is "full"? I don't think the brain can be full. Your examples are awesome, but IMO they show that the brain has an amazing plasticity and can adapt to various changes very well.
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reserve here. It sounds as if there is some backup storage that is currently unused, but can be activated if necessary. IIRC, after a damaging event such as a stroke, restructuring often leads to the loss of skills, such as being able to speak a foreign language. So for me it's not a reserve, but a severe restructuring. I think the problem of the question is that capacity in terms of the brain is ill defined.
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