Event-related potentials in post-traumatic stress disorder of combat origin

Visual event-related potentials (ERPs) of primary interest in this study of post-traumatic stress disorder (PTSD) were N1, N2, P2, and P3. Forty Israeli combat veterans consisting of 20 PTSD sufferers and 20 normal controls were evaluated. ERPs were recorded in response to three sets of computer-generated visual stimuli, presented in the form of a modified oddball paradigm. These stimuli included: domestic animal pictures (targets), emotionally neutral pictures of furnishings (nontargets), and combat-related pictures (nontarget probes). Subjects were required to discriminate between target and nontarget stimuli by pressing a button in response to target stimuli only. Subjects were instructed to ignore all nontarget stimuli. As expected, target stimuli evoked accentuated P3 amplitudes in both controls and PTSD patients. The nontarget combat-related pictures elicited enhanced P3 and N1 amplitudes in the PTSD patients only. N2 amplitudes were accentuated in PTSD patients for both targets and combat-related pictures. P3 latencies and reaction times to target stimuli were prolonged in PTSD patients. The same tendency was observed for N1 latencies. These results may indicate that an altered state of early and late cognitive selective attention processing exists in PTSD patients in addition to a vulnerability to traumatic reminiscences.