We actually use ALL of our brain but we only understand about 10% of how it functions. It's quite complex and depends on the kind of seizures you suffer with that determines how much of your brain is affected. Neurologists still don't understand how/why in most cases why some seizures start in a region of the brain but don't spread to the rest, they don't know what the story is with generalised seizures.
Disregard genius comment from @A MyEpilepsyTeam Member, doesn't take a genius to work out that we got a shit deal.

Everyone with Epilepsy are different. Depending on the type of Epilepsy and seizures will depend on how much of your brain and what areas the brain activity is located. There can be more than 1 area of the brain that can have seizure activity. Dealing with brain injuries , will depend on where there seizures maybe active. Whether it be one or more areas of the brain.

Now if it has to do with genetics or a form of illness is a whole new bag of worms.

I don't mean before or during a. Seizure I mean. Like just on a regular base you have regular dreams but once in a while I get a very detailed vision and it will play out like this ...example when my grandmother died I had a dream about me waking up seeing the fire department run past by for me running to my mom says don't take her think it was the cops trying to take my mom then I looked up at my mom she looked at me with tears in ber eyes and then looked over at my grandma that they were doing cpr on well then I woke up was relieved it was just a dream but then the fire department ran past my door for real then the hole thing played out just like my dream ..I have been able to tell people some time of something that about to happen to them before it does soe. Time I not Shure if it has anything to do with epelepsy or not but I was wondering if other people have thing like that happen