Preattentive Processing Abnormalities in Chronic Pain: Neurophysiological Evidence from Mismatch Negativity

Objective. To investigate the characteristics of mismatch negativity (MMN) in chronic pain patients and the effect of chronic pain on MMN morphology in order to supply the neurophysiological evidence on preattentive processing abnormalities in chronic pain patients. Study Design. We evaluated the auditory MMN to frequency deviance in patients with chronic pain and healthy controls. Emotion was assessed using the Beck Depression Inventory-II (BDI-II) and the Beck Anxiety Inventory (BAI), and pain intensity was assessed using the short-form McGill Pain Questionnaire (SF-MPQ). Subjects and Settings. Subjects included 20 outpatients with chronic pain lasting for at least 6 months and 20 healthy controls. Results. MMN latencies in chronic pain patients were significantly delayed relative to healthy controls (P < 0.001). MMN latency was positively correlated with duration of chronic pain and negatively correlated with the SF-MPQ affective index. MMN amplitudes were similar between chronic pain patients and controls, and MMN morphology did not correlate with age, education level, BDI, BAI, visual analog scale, or the SF-MPQ sensory index. Conclusions. The preattentive processing speed in chronic pain patients is decreased; the longer a person experiences chronic pain and the more severe the affective component of pain are, the more likely they are to demonstrate preattentive processing difficulties.