The man that Rain Man was loosely based on was a man by the name of Kim Peek. It was found that he was born without this bridge. This gave him something called Savant Syndrome, which means that his brain wired itself in a particular way that gave him abilities which can only be achieved by Neuro-typical people through the use of computers. He was a brilliant man who only had one personality, this is because his brain wired itself in such a way (which happens primarily between the ages of eighteen months and two years) to take into account the missing bridge.
When a Neuro-typical person has this bridge removed, vital links will be lost. The brain is unable to rewire itself to compensate for this in most cases of brain injury.
In rare cases the brain can rewire itself to circumvent the damaged section. Typically this occurs when the left temporal lobe is damaged resulting in lost functions being reallocated to the right temporal lobe, and taking up space in untapped, undamaged grey matter. This process gives the person Savant Abilities, which vary from Human Calculators to Musical Geniuses.
This condition is called Acquired Savant Syndrome, and there are less than 100 recorded cases in the world. I happen to be one of them.
One of the after effects of my rewiring is Visual Thinking. My thought process when it comes to Engineering problems occurs via a cascade of images like a train of evidence, with each piece leading to the next. It is impossible for me to explain my "Working out" of a problem, but I can communicate the final solution or result into cognitive sentences. Sometimes though, it is easier to just draw it.
To my way of thinking, if I were "linked" to someone else's brain/mind it would be achieved through an exchange of images rather than "hearing" a persons speaking voice in ones head. It would be crucial for each individual to maintain control of this "Channel" enabling them to turn it on or off or switch to other people in a similar way to controlling a T.V.
Without this control a person would simply go mad. Imagine watching 2 or more T.V. shows at the same time, all the time, having the shows picked by other people, and not having the option to ever turn the T.V. off for a quiet night with a book. Also, sleeping would be next to impossible.
I fail to see how any of this can be connected to a soul in any way, shape or form. The concept and definition of a soul relies on the fact that each person possesses a unique personality, a unique way of thinking, and a unique energy/soul.There is no correlation or causation between the two things. Your question is a bit like asking someone what they think the air velocity of an Elephant would be if it had wings. It is something which cannot possibly be quantified, so why ponder on it.

If the soul was real and a person had amnesia, does he now have two souls? Like one that goes to hell for all the bad things he did. And another that can't remember those bad things, so they aren't really a part of him and gets to go to heaven. Or does he go to hell for the things he can't remember? In so many ways, the soul doesn't make any sense.

How does this disprove a soul?