Matt Cutts from the Quality Group at Google and a popular Webmaster Guide in the Internet world has stated that keywords separated with underscores are treated the same as keywords separated with hyphens.
Matt Cutts from the Quality Group at Google and a popular Webmaster Guide in the Internet world has stated that keywords separated with underscores are treated the same as keywords separated with hyphens.

Not true. please read this statement
http://www.mattcutts.com/blog/dashes-vs-underscores/