1. ¹The Brain Dynamics Centre, Westmead Millennium Institute, Westmead Hospital and Western Clinical School, University of Sydney, Westmead, NSW, Australia
2. ²Psychological Medicine, Western Clinical School, University of Sydney, Sydney, NSW, Australia
3. ³Prince of Wales Medical Research Institute, Sydney, NSW, Australia
4. ⁴University of New South Wales, Sydney, NSW, Australia
5. ⁵School of Psychology, University of Sydney, Sydney, NSW, Australia
6. ⁶Department of Psychology, Behavioral Neuroscience, University of Missouri, St Louis, MO, USA
7. ⁷The Brain Resource Company and Brain Resource International Database, Ultimo, NSW, Australia
8. ⁸NICTA and School of Information Technologies, University of Sydney, Sydney, NSW, Australia
9. ⁹Laboratory of Personality and Cognition, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA

Correspondence: Professor LM Williams, The Brain Dynamics Centre, Westmead Millennium Institute, Westmead Hospital, Westmead 2145, Australia. Tel: +61 2 9845 8195; Fax: +61 2 9845 8190; E-mail: lea_williams@wmi.usyd.edu.au

Received 16 May 2008; Revised 14 December 2008; Accepted 15 December 2008; Published online 4 February 2009.

Abstract

Association studies suggest that the low activity variant of the monoamine oxidase A (MAOA)-uVNTR polymorphism confers risk for emotional disturbances associated with antisocial traits, particularly in males. Here, we assessed the low (MAOA-L) activity variant in relation to both brain function and a behavioral index of antisocial traits. From an initial sample of 290 healthy participants, 210 had low (MAOA-L) or high (MAOA-H) activity variants. Participants underwent a brief assessment of personality traits and event-related potential (ERP) recording during an emotion-processing task. Genotype differences in ERPs were localized using LORETA. The MAOA-L genotype was distinguished by elevated scores on the index of antisocial traits. These traits were related to altered ERPs elicited 120–280ms post-stimulus, particularly for negative emotion. Altered neural processing of anger in MAOA-L genotypes was localized to medial frontal, parietal, and superior temporo-occipital regions in males, but only to the superior occipital cortex in females. The MAOA low activity variant may increase susceptibility to antisocial traits through alterations to the neural systems for processing threat-related emotion, especially for males. Monoamines such as noradrenalin and serotonin may modulate these relationships, given that their metabolism varies according to MAOA variants, and that they modulate both emotional brain systems and antisocial aggression.