Exploring the optimal site for the localization of dorsolateral prefrontal cortex in brain stimulation experiments Paul B. Fitzgerald, MBBS, MPM, PhD, FRANZCP a , Jerome J. Maller, BSc, GradDipPsych, MSc, PhD a , Kate E. Hoy, BBNSc (Hons), DPsych (Clin Neuro) a , Richard Thomson, BEng (Hons), PhD a , Zafiris J. Daskalakis, MD, FRCP(C) b a Alfred Psychiatry Research Centre, The Alfred and Monash University School of Psychology, Psychiatry and Psychological Medicine, Melbourne, Victoria, Australia b Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada Background Dorsolateral prefrontal cortex (DLPFC) is a common target for repetitive transcranial magnetic stimulation (rTMS) experiments and therapeutic protocols. Objective The aim of this study was to investigate the optimal method for the localization of DLPFC for use in these studies. Methods Twelve healthy subjects underwent a structural magnetic resonance imaging (MRI) scan, a TMS procedure to establish the location of the motor cortex and a neuronavigational procedure to assess the relative position of the DLPFC. Several electroencephalographic (EEG) points and a position 5 cm anterior to motor cortex were established. Results The DLPFC site used was identified as being approximately halfway between the EEG points F3 and AF3. This point is considerably more anterior than the point identified by measuring 5 cm anterior to motor cortex. The study was supported in part by a National Health and Medical Research Council (NHMRC) project grant (436710) and the Neurosciences Australia Clinical Neurobiology of Psychiatry Platform. PF and ZD have received support for research conducted with Neuronetics Inc, a TMS equipment manufacturer. PF was supported by a Practitioner Fellowship grant from the NHMRC and ZD by a NARSADYoung Investigator award. Correspondence: Professor Paul B. Fitzgerald, Alfred Psychiatry Research Centre, First Floor, Old Baker Building,The Alfred, Commercial Rd Melbourne, Victoria, Australia, 3004. E-mail address: paul.fitzgerald@med.monash.edu.au Submitted January 8, 2009. Accepted for publication March 4, 2009. 1935-861X/09/$ -see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.brs.2009.03.002 Brain Stimulation (2009) 2, 234–7 www.brainstimjrnl.com