Changes in mismatch negativity across pre-hypnosis, hypnosis and post-hypnosis conditions distinguish high from low hypnotic susceptibility groups.

The role of alterations in mismatch negativity (MMN) in hypnosis was examined by recording MMN of the auditory ERP at frontal (F3, Fz, and F4) and mastoid (M1 and M2) placements. Frontal MMN is believed to reflect activity in right anterior cortical generators, whereas MMN at mastoid leads reflects generators located bilaterally in the temporal auditory cortex. MMN recordings were obtained in 11 low and 12 high hypnotically susceptible participants in three successive blocks; pre-hypnosis, hypnosis and post-hypnosis. Frontal (but not temporal) MMN showed a significant quadratic trend across testing conditions. It increased during hypnosis and then dropped post-hypnosis for both susceptibility groups. Linear trends for frontal and temporal MMN showed directly opposite patterns of change in the interaction between hypnotic susceptibility and testing blocks. Frontal MMN built up linearly over the test blocks in high relative to low susceptibility participants. Temporal MMN showed the reverse pattern and increased linearly across test conditions in those with low relative to high hypnotic susceptibility.