The disruptive effect of chronic pain on mismatch negativity.

Objective: To investigate the effect of chronic pain on processes that generate the mismatch negativity (MMN).
Methods: Twelve participants with a diagnosis of chronic intractable pain were tested before and after pain treatment. During testing, event-related potentials were recorded while participants performed tasks of varying difficulty.
Results: The amplitude of the MMN was found to be greater following a nerve block procedure compared to MMN amplitude when participants were experiencing chronic pain. This effect was found to occur in the MMN for difficult-to-detect tones elicited while participants were performing a simultaneous cognitively demanding visual task. MMN amplitude was found to be greater with attention to difficult-to-detect deviants during pain but not in no pain conditions.
Conclusions: These results provide an electrophysiological correlate of previous findings that high levels of pain disrupt cognition during the performance of demanding tasks.