1. ¹Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, UK
2. ²Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford, UK
3. ³Centre for Functional Magnetic Resonance Imaging of the Brain, John Radcliffe Hospital, Oxford, UK

Correspondence: BA Völlm, Neuroscience and Psychiatry Unit, University of Manchester, Stopford Building, Oxford Rd, Manchester M13 9PT, UK. Tel: +44 161 275 7670; Fax: +44 161 275 7429; E-mail: birgit.vollm@man.ac.uk

Received 22 September 2003; Revised 8 March 2004; Accepted 12 March 2004; Published online 12 May 2004.

Abstract

Amphetamines are highly addictive drugs that have pronounced effects on emotional and cognitive behavior in humans. These effects are mediated through their potent dopaminergic agonistic properties. Dopamine has also been implicated in the modulation of responses of the 'reward circuit' in animal and human studies. In this study we use functional magnetic resonance imaging (fMRI) to identify the brain circuitry involved in the psychostimulant effect of methamphetamine in psychostimulant-naïve human subjects. Seven healthy volunteers were scanned in a 3T MR imaging system. They received single-blind intravenous infusions of methamphetamine (0.15 mg/kg), and rated their experience of 'mind-racing' on a button press throughout the experiment. Data were analyzed with statistical parametric mapping methods. Amphetamine administration activated the medial orbitofrontal cortex, the rostral part of the anterior cingulate cortex, and the ventral striatum. Ratings of 'mind-racing' after methamphetamine infusion correlated with activations in the rostral part of the anterior cingulate cortex and in the ventral striatum. In addition, activations in the medial orbitofrontal cortex were independent of motor and related responses involved in making the ratings. These findings indicate that the first administration of a psychostimulant to human subjects activates classical reward circuitry. Our data also support recent hypotheses suggesting a central role for the orbitofrontal cortex in drug reinforcement and the development of addiction.