I added Petra backports to linux Mint 13, and lost some of the touchpad functions, until I found the solution given by robin at:viewtopic.php?f=49&t=145054&p=799328&hilit=touchpad&sid=5db7e082d4590a906e14f3e121455ab4#p799328
I used the command "gsettings set" twice, because I had those two lines:
when I sent the command gsettings list-schemas.
Also anadrkris helped with his additional comments.
Thanks to both of them.