Actually, yeah, they do...

There have been studies done where the patient is under local anesthesia and doctors take thin probes and slowly stimulate each section of the brain and "map" out what sections control responses by asking questions and judging reactions.

They do it so in case there is a patient with a tumor in one part of the brain and they want to operate. They have to know if they are going to affect the speech center, the co-ordination center, destroy memory or other more vital ares by removing the tumor.

I'm going to say I thought I understood until I experienced certain things for myself.
I'm fluently bilingual in English and Spanish. Speak, read and write in both languages.
I noticed a long time ago that when I'm tired toward the point of exhaustion, I lose my ability to speak Spanish, even though it's my native language.
I don't drink often, much less get actually drunk. But in an occasion I did a few years back, I noticed the alcohol makes me lose my vocabulary in English.
Scientists say your language abilities reside in some part of the brain.
If that is so, wouldn't all language abilities reside in the same part? And wouldn't they all be affected equally when operating under impaired conditions? Or does it matter the conditions of the impairment?
Just curious
Oh. Now that you have me thinking,
A third kind if impairment comes from migraines. Why when I have a migraine on th right side if my head does it seem like I have a higher tolerance for pain before the pain brings on nausea?
Yet when it occurs on the left side it seems to hurt less but make me nauseated sooner?

My son was brain damaged at the age of 13 from a text driver.

I'm not going to get into this topic but let me just say they know.

Well actually it's all falsifiable hypothesis, the very first rule of true science.

Most brain mapping was done between the late 19th and early 20th centuries, much of it France, most of it by studying the effects of brain trauma and the results of brain surgery.
It is by inferrence.

More recent medical research, in the last few years in Germany and Wales have found that in fact brain mapping is erroneous, that brain function is actually amorphous and not confined to specific regions, but happen upon specific regions by evolutionary convenience only as a likelihood.

eg. one German patient in particular was born with only the right hemisphere of her brain, the left hemisphere left unformed and useless. In early childhood she had many troubles and experienced fits and siezures, however by her late teens her right hemisphere had adopted virtually all normal brain function that anybody has, and currently doctors describe her as a happy and intelligent young lady with a great sense of humour.

Similarly severe brain trauma victims and post brain surgery outpatients with entire sections of their brains removed have subsequently recovered most or all healthy brain function as it simply moves somewhere else when the place it normally resides is lost. Again this is published in medical journals and directly challenges the neurological assertion of regional brain function.

Where brain mapping came about however, was in the field of psychiatry, in modern times evolved as neurosciences, its role is largely in therapeutic treatment as opposed to surgical. Neurosurgery causes brain trauma to save a life, it's the therapists who have to try to work at rehabilitation following surgery. And brain mapping, whilst fallacious in the strictest biological sense, is an effective tool for them to use to help with that.

Put simply, if your speech centre of the brain is cut out, assuming a healthy lifestyle and effective therapy, your brain will simply reinvent that same brain function somewhere else.

Put simply, if your speech centre of the brain is cut out, assuming a healthy lifestyle and effective therapy, your brain will simply reinvent that same brain function somewhere else.