|MadSci Network: Neuroscience|
This myth that "nine-tenths of your mental potential lies unused" is peddled by advertisers, not by mainstream scientists. It's a tempting thought that some new learning technique or mind-altering substance could unlock our potential to be superbeings. Sadly, there is no evidence to support it from neuroscience, rather the reverse. Neurological disorders, like Parkinson's Disease, affect only specific areas of the brain. The damage caused by such conditions is far less than damage to 90% of the brain. Yet, their effects are devastating and in time fatal. It is true that at any one time some parts of the brain are much more active than others, as can be shown using brain imaging techniques. When we speak a foreign language, certain language centres become highly active, or when we are making fine movements with our hands such as watchmaking, other movement control centres are highly active. However the rest of the brain is not sitting around pointlessly - it is either involved in background activities to maintain posture, attention, visual attentiveness, speech, etc that are needed for these activities, or regions of the brain with other 'jobs' such as the auditory and olfactory cortex regions (specialised brain regions involved in hearing and smell functions respectively) are ready for an input. The visual cortex for example is highly specialised and if we have our eyes closed we are not 'using' this part of the brain much, but becase it is specialized it cannot be immediately employed for other functions. Remodelling of brain structures to meet new needs is possible, particularly in the young who have more 'plastic' nervous systems than adults. But while not all the brain need be actively involved in every task at all times, we certainly do not have a big black hole of a brain with little spots of light that are all that is ever used. As for references, online sources of information on this topic include the following.
Try the links in the MadSci Library for more information on Neuroscience.