User Account Creation - User Name Defaul

Summary

Change Default for User Name

Content

Hello -

Can someone point me to where I can change what is being used as the "User Name" for account creation?  We currently have it set to be the email address but would like to change it to Person ID.  We've already renamed all of our accounts but now need to change the default before we run the next Import User Process.

Thanks in advance!

Becky