In the movie, As Good As It Gets, Marvin Udahl, the main character played by Jack Nicholson, has a persona (grumpy, difficult, eccentric, OCD) that is very different from his voice (think more Nicholas Sparks.)
Asked by an emotional woman how he writes women so well, he said something akin to "taking away all reason." Grumpy guy who has figured out how to write for an emotional market, that's all.
When I first read one of Nicholas Sparks' books (after seeing two of his movies) I cynically concluded here was a guy who had figured out how to make millions by making people cry. Book after book.
However, after reading Nicholas Sparks' autobiographical piece, Three Weeks With My Brother, and seeing how acutely affected he was by a very difficult upbringing and through life challenges presented to him as an adult (which I completely understand) I do get how his work seems to be written with every raw nerve exposed. I have since concluded he is definitely an emotional kind of guy who feels things deeply -- or at least his persona is of that kind of person.
The persona he presents autobiographically is very like his voice. He comes across as just as empathetic and emotional and heart-on-his-sleeve as his writing.
I don't know him personally, so I don't know if his persona is really what his personality is like when he is alone or with his family -- but I have no reason to think it's different than he presents in his autobiography.
There's a debate on Mediabistro.com about the difference between persona and voice. http://mediabistro.com/bbs/cache/t38812_1.asp There can be a difference -- or they can be very closely related.