A quick answer... Please refer to your

• Poser 6 Reference Manual: p. 147; p. 229; (maybe) p. 310; p. 321; p. 342
• Poser 6 Tutorial Manual: p. 125
  There is only 1 displacement channel that should not be confused with the bump map channel if you look in the material room advanced settings. It's somewhere towards the lower end near the alternative node channels.

You can connect math nodes to the displacement channel, but more often a simple b/w image map is connected to it.