Theory of mind (ToM) refers to the ability to infer other's mental states. It includes a recognition that other individuals experience thoughts, feelings, intentions, and desires that may be different to our own. ToM is often impaired among individuals with an autism spectrum disorder (such as autism and Asperger's disorder), and may underlie aspects of social dysfunction in this population. Indeed, it has been suggested that impaired ToM is the core deficit of autism and Asperger's disorder.

Imaging studies suggest that the bilateral medial prefrontal cortex, the most important brain region in ToM processing, is underactive in autism. The current study examines whether repetitive transcranial magnetic stimulation (rTMS) to the bilateral medial prefrontal cortex can modulate ToM ability among healthy adults, and improve ToM ability among adults with autism or Asperger's disorder. With the prevalence of autism increasing, there is a clear need to develop appropriate therapeutic interventions to improve social functioning.

This study involves a double-blind study using high-frequency rTMS in an attempt to improve ToM among adults with either autism or Asperger's disorder. Theory of mind will be measured using behavioural tasks that require the participant to infer what someone is thinking or feeling by observing their behaviour. These tasks will administered both before and after rTMS to determine whether any change in theory of mind has occurred.

Thirty adults with either autism (n = 15) or Asperger's disorder (n = 15) will initially undergo functional and structural MRI to determine the site on the scalp that lies over the medial prefrontal cortex (to which rTMS will be administered). They will then attend our lab each consecutive weekday for a two-week period, during which they will 15 minutes high-frequency (5 Hz) rTMS (either active or sham) to the medial prefrontal cortex. ToM and clinical measures will be collected before the first session, soon after the last session, and one month after the last session.

Based on prior imaging data, it is expected that high-frequency rTMS (compared with sham rTMS) to the medial prefrontal cortex will improve ToM ability and reduce social dysfunction among adults with autism or Asperger's disorder. Should these hypotheses be supported, it will indicate the suitability of rTMS as a neurobiological intervention designed to improve ToM and social function among individuals with autism and related disorders.