The mismatch negativity (MMN) is observed following rare or unique sensory events, and reflects pre-attentional sensory processing of unexpected stimuli. The MMN is altered in several mental illnesses, including post-traumatic stress disorder (PTSD), but did not yield consistent results. We measured MMN in 27 survivors of the Wenchuan earthquake, including 13 who were diagnosed with PTSD, to determine if pre-attentive processing in the auditory cortex was altered by this disease. The amplitude of MMN was significantly greater in the PTSD group compared to the control group. In contrast, no significant group difference was found in the N1 potential, an event-related potential that reflects cortical transmission of sensory information. These results demonstrated an increased sensitivity to deviant stimuli in PTSD that may reflect a chronic state of hyperarousal and hypervigilance in trauma victims.
