I recommend Hemispheric asymmetry: what's right and what's left by Joseph B. Hellige (2001) for some interesting information. Note that I am not a professional in this field, however.
They called it speech, but talked about it in a way that implicated deeper human interactions.
Through biofeedback it might be interesting for people to introspectively learn the connection between philosophy (in a broad sense, meaning all of the thought approach to life) and meatware activity. I am a believer in a trans-physical soul, but also that God has made a creation in which body is normally employed to carry out many of the intentions of the soul and to bring back certain information to the soul.
Oh, and I didn’t mean to say that I thought said reflection had to symmetrically map into the brain. It would be like a computer with two cores designed to optimize different kinds of tasks. The software calls on the floating point unit, say, for one thing, and on the integer arithmetic unit for other things.
Oh again, thank you for the more modern references.