To separate a high level area of the pattern from a lower level area you can use the stop cut. This is a two stroke cut made with the bench knife.
Place your bench knife on the pattern line, angle the blade slightly towards the area outside the line. Pull the stroke with even pressure making a shallow cut line. Lift the knife from the slice and re-position it at the beginning of the pattern line. This time angle the knife slightly towards the inside of the pattern area, pull the stroke. This will release a v-trough shaped slice of wood. For deep stop cuts you can re-cut this area several times, slowly dropping the trough to your desired depth.
You can now use your round gouges to lower the background area, gliding the gouges into the stop cut. The stop cut literally stops the gouge from cutting the higher area, giving you control over the gouge cutting stroke.