What are some things that neuroscientists know but most people don't?

I would say one thing we realize is that we understand relatively little about how the brain functions.  It was only within the last 10 years that we realized the majority of the energy consumption by the brain is not used for conscious response to the outside world (Dark energy [1]).  We discovered the default mode network which is more active during rest and sleep than during attentive states.

The energy consumed by this ever active messaging, known as the brain’s default mode, is about 20 times that used by the  brain when it responds consciously to a pesky fly or another outside stimulus. [2]

[1] http://www.sciencemag.org/content/314/5803/1249.full
[2] http://www.scientificamerican.com/article.cfm?id=the-brains-dark-energy

Neuroscience can explain why so many people believe they have been abducted by aliens. There is a phenomenon called sleep paralysis which is surprisingly common.  In surveys from Canada, China, England, Japan and Nigeria, 20% to 60% of individuals reported having experienced sleep paralysis at least once in their lifetime. [3] Sleep paralysis can occur when you are falling asleep or waking up.  When you are falling asleep the body will go into REM sleep while you are still aware.    You can also become aware before a REM cycle is complete.  The significance of this is that while in REM sleep you are in a state called REM atonia [4] which paralyzes your body so that you do not act out your dreams.  So when people experience sleep paralysis they are conscious but not able to control their body.  Often times this can be accompanied by "hallucinations/dreams" and people will attribute the bizarre experience to an alien abduction.



[3] http://en.wikipedia.org/wiki/Sleep_paralysis
[4] http://en.wikipedia.org/wiki/REM_atonia#Physiology

Body image, the brain can believe that an amputated limb is still there.  This is called the phantom limb and it is very common.  Approximately 60 to 80% of individuals with an amputation experience phantom sensations in their amputated limb, and the majority of the sensations are painful. [5]  This can be a very painful syndrome because the phantom limb will often get stuck in a extremely painful cramped position and the amputee will have no way to stretch the limb and stop the pain.  The phantom limb was essentially untreatable until one neuroscientist, Dr. Ramachandran came up with a remarkably simple treatment.  All he did was make a box with a mirror in it and had the amputee put his intact limb in one side and the amputated limb behind the mirror on the other.  The amputee then moved the intact limb and saw in the mirror his phantom limb moving which tricked his brain into relieving the pain in the phantom limb.  Although the brain is incredibly advanced and "intelligent" it is remarkably easy to trick it.


[5]  http://en.wikipedia.org/wiki/Phantom_limb

This was an answer I wrote on Quora.