 Stimulation localisation This will follow standard procedures. Firstly, the site for the optimal activation of the abductor pollicis brevis muscle in the contralateral hand will be located whilst stimulating the relevant motor cortical region at supra-threshold intensity. This site will be marked on the scalp. We will then measure 6 cm anteriorly on the scalp surface and mark it with ink. This point will be then used as the site of stimulation. The majority of rTMS studies have measured 5 cm anteriorly. However, this has been shown to result consistently in localisation that is posterior to the dorsolateral PFC 37. The measurement described here should result in more consistent treatment of dorsolateral PFC but still provide considerable stimulation overlap with the established 5 cm site. 