The event related potentials in a population free from substance abuse or psychotrophic drug use and to compare their results with normal individuals

Introduction: Event related potentials (ERPs) have been used in many studies investigating the neurophysiologic causes of aggressive behavior. Verbal skills and P300 evoked potential amplitudes of aggressive individuals that demonstrate impulsive behaviors have been shown to be lower compared to aggressive individuals without impulsive behaviors. Although Raise et al have stated the opposite according to results of their study in 1988, current literature support that P300 amplitudes are reduced in antisocial individuals(1). Antisocial personality disorder (ASPD) is frequently associated with substance abuse; which might reduce the reliability of the studies on this subject(2). However, sample population of our study included antisocials doing their military service, thus representing a more refined population in terms of substance abuse compared to civilian lifestyle. The purpose of our study was to measure the event related potentials in a population free from substance abuse or psychotrophic drug use and to compare their results with normal individuals. Method: Study included 42 patients with ASPD that had a high score in Buss Perry Aggression Scale with no Axis I diagnosis in his psychological history according to DSM-IV and no organic disease or mental retardation in physical, neurological and psychological examination, who were at least primary school graduates with a certain intellectual level to complete the tests and a control group of 44 healthy individuals that consented to participate to the study. Study and control group were selected from those did not use a psychotroph or any other substance for at least 15 days. Auditory ERPs were measured in all cases. Numerical values were compared by the test and significance level was set as p<.05. Antisocial individuals with higher aggression scores showed significant differences for P1 Fz latency and amplitudes, P2 Fz latency and amplitudes (p<.01), and N2 latency and amplitudes (p<.05) compared to control group. Discussion: Results of our study (Table 1) showed that event related auditory potentials of patients with ASPD that were measured from frontal and parietal areas demonstrate lower P3 amplitudes compared to records of normal individuals. This finding suggests that attention and working memory area may be affected in antisocial individuals. Patients with ADHD were shown to have lower P1 components compared to normal (3). In our study, P1 components were lower compared to control group, which suggest that P1 components of antisocials might have similarity with that of patients with ADHD. N2 was also found to be lower compared to controls. Barry et al have proposed that N2 is correlated with frontal inhibition(4). This finding also suggests that difficulty in impulse control of antisocial individuals may be associated with lack of frontal inhibition.