How do the cockpit controls of a tiltrotor aircraft work?
This video explains it nicely starting at about 1:20 in. 

Also see here.

This is a pretty interesting article on flying it as well. It really seems to depend on mode but its summarized here nicely,


  Climbing into the front seats of the Osprey definitely does not
  produce the most graceful entrance: it requires some contorting around
  the armrest, center console and overhead panel. The cockpit is
  dominated by four night-vision-goggle-compatible, six-inch-square
  multi-function displays that allow access to flight, navigation and
  system information. Mechanical flight controls consist of a center
  control stick, thrust control lever (TCL) and rudder pedals. The
  control stick functions as cyclic control while in conversion and
  helicopter modes, but steadily fades into a traditional airplane
  control stick as the nacelles transition to airplane mode.
  
  The TCL
  moves fore and aft just like an airplane throttle, unlike a helicopter
  collective. It does operate as a collective control, however, and
  becomes a traditional throttle during the transition. While this may
  seem counter-intuitive to helicopter pilots, it actually makes a lot
  of sense, because regardless of the mode of flight, youre always doing
  the same thing: controlling the thrust vector. Forward on the TCL in
  helicopter mode is the same as raising the collective in a helicopter,
  and vice versa. The first couple of hours for helicopter pilots
  transitioning to the Osprey highlight a bit of collective dyslexia,
  but very quickly it never becomes a further problem. A spring-loaded,
  knurled rotary knob on the TCL that lies in contact with the pilots
  left thumb controls the nacelles. Roll the thumbwheel aft and the
  nacelles rotate to the vertical, roll it forward and the nacelles
  continue to the downstops. The controls follow the hands on throttle
  and stick, or HOTAS, concept, and have all the controls necessary on
  them to control multiple systems on the airplane.