When researchers Raji et al. (2004) looked at the brain activity of 14 highly hypnotizable individuals interesting findings emerged. They were asked to take part in three procedures. The first was to imagine pain in their left hand, the second involved going in to a state of hypnosis and being subjected to pain delivered by laser pulses and thirdly to experience the laser pulses in a non-hypnotized state. There was activation in the caudal anterior cingulate cortex and the middle insula in all three procedures. These areas of the brain would be associated with emotional processing of the pain. In both the second and third conditions (the physically induced laser pulse conditions) the sensory component of pain was registered by the participants as being stronger - a visual analog scale was used. In the psychological condition where participants imagined the pain becoming intolerable and then drifting away from them there was more activation in the caudal anterior cingulate cortex which the authors stated was probably due to the emotional processing of pain.
Regardless, it would seem that for highly hypnotizable individuals the same brain areas, albeit to different degrees, are activated irrespective of whether the pain is real or imagined..