Event-related potential studies of post-traumatic stress disorder: a critical review and synthesis

Although post-traumatic stress disorder (PTSD) is classified as an 'anxiety disorder', evidence of cognitive and information processing (IP) abnormalities in PTSD has been accumulating [1]. While many studies on emotional processing abnormalities in PTSD exist, event-related potentials (ERPs) studies focusing on early stages of IP abnormalities in PTSD are limited in number. The aim of this review was to summarize ERP findings in PTSD and determine whether there are consistent patterns of IP deviations reported in this disorder. We also sought to gain possible insight into clinical correlates of these differences. Another aim of this review was to assess if we could present suggestions for future research methods.Brain ERPs are the main tools available for clinical investigators to probe IP in real time, as they can assess different phases of IP in the human brain [2]. Abnormality of the initial phase of IP (the 0 to 20 ms following auditory or visual stimulation), where information is conducted through subcortical structures on its way to the cerebral cortex, is usually linked to brain stem abnormalities [3]. Abnormalities at this stage of IP are rarely reported in psychiatric patients [4]. Due to the extremely small number of ERP studies examining this stage of IP in association with PTSD, this IP stage is not further discussed in this report.The midlatency range of information processing (following the early stage and spanning 20 to 200 ms following stimulation), when signal registration and filtering out (gating) of redundant information takes place [5], has been shown to be abnormal in a large number of psychiatric and neuropsychiatric conditions [6]. Auditory midlatency range is represented by three major event-related response components: the P50 (40 to 80 ms), N100 (75 to 150 ms) and the P200 (150 to 250 ms) [7]. Two variables are routinely examined in association with all ERPs: amplitude (how large the response is) and latency (how long after the stimulus t