It's amazing how many writers struggle to write clear, cohesive, streamlined sentences. Even some of the best writers have to think carefully as they build their sentences in order to ensure that they communicate clearly.
Have you ever read your sentences aloud and thought "This doesn't sound right"? It sounded correct when you were in the throes of your creative writing frenzy, but now that you're speaking them, they don't sound quite right.
Well, that may be the fault of your brain--or, more specifically, the part of your brain that supports writing!
A study was published in the journal Psychological Science, detailing how writing and speaking are supported by two different parts of the brain. Writing is more than just the motor control that moves your hand to write or type, but the high-level creative aspects of putting words in a sentence just right.
The researchers in the study found that damaging the "writing" part of the brain did nothing to affect speaking, and vice versa. The two portions of the brain remained separate from the other, as if there were two language systems in your brain.
When you speak, you may say "Bob is running", but when you write, it comes out as "Bob runs". This is because the way you talk is different from the way you write, and it's all thanks to the marvelous creation that is your brain!
Talk with any author, editor, or professional writer, and they will tell you the truth: writing is NOT like talking. You can't write the same way you would talk. Even when writing dialogue, you have to be careful not to slip too far into writing "speech".
Verbal communication is very different from written communication, and you need to approach each from a different angle! When writing, you need to structure your sentences not the way you would say them around, but the way they SHOULD be structured--using the proper grammar, avoiding passives, limiting adverbs, and all the other finicky rules for writing. You CANNOT write the way you speak, else your writing will be both amateur and incorrect!