YOU GET NO BRAIN DAMAGE FROM THIS
Getting brain damage from this would be like getting brain damage from every time you have a migraine. What happens is the blood flow needs to speed up and pump faster to the brain but when you do these things it goes from low to high really fast. A migraine is when only a section of your brain has low blood to it and it happens longer then 5 seconds. Once blood starts pumping into that section you get a migraine headache, from the sudden increase of blood.
Also this is just a more intense form of when you suddenly stand up, you've all experienced this but not as intense.