From my own experience, and from the general brain scientific point of view, writing has a special significance for the brain.
My mentor at the University of Cambridge was Horace Barlow. Once, Horace was organizing a conference. One of the participants did not send in an abstract. When contacted, the negligent participant answered that he did not know what he should write in the paper. When the postdoc who was functioning as an assistant for the conference reported that reply, Horace immediately said:
"Why doesn't he write and find out?"
Horace's sharp comment cuts right into the essence of the cognitive processes involved in writing. When writing, one often consciously perceives chunks of information which has been dormant in one's unconscious. Writing provides a channel between one's conscious and unconscious.