Dual brain theory
(As noted link lacks expert author)
Post corpus callosum separation
A post-operative patient reported that one morning she was awaked
by her own hand. Her left hand (right brain) slapped her across the
face. Her alarm clock had failed to go off; she had over slept for an
appointment that she needed to keep. She could not understand why she
had hit her own face. However, because she had awakened herself, she was
able to get to her appointment on time.
Not personally having heard this person's voice but from what I have read the person's speech does not seem to be affected even though the left tongue has different innervation than the right tongue. It would seem to argue either that the left brain either controls or influences the left tongue or the left tongue is not particularly active in the mechanics of speech. (The right brain would control the left tongue normally)
Although VP showed no evidence for transfer of color, shape or size, there was evidence for transfer of word information.
What I feel to have is a left tongue that is separate from the right tongue and that I previously had no sense of it as independent. It is as if it did not exist for me. The left tongue/throat seems to influence how I use the whole left side and therefore both sides of my body. The left tongue seems to influences my left jaw and hyoid which appears to impacts the skull and it's position on the axis and atlas of the spine which feels to involve the musculature of the neck etc
I imagine most people are on a continuum with many more naturally symmetric or in a way having a better sense of their right and left 'needs' than I do.