al., 1996). Similarly, stimulation of an equivalent rostral CMA region in awake humans caused them to be unable to resist the urge to move towards and grasp objects within their range (Kremer, Chassagnon, Hoffmann, Benabid and Kahane, 2001). More than simply being involved in any type of movement, it seems that dorsal ACC is particularly concerned with situations where a response has to be generated voluntarily rather than being guided by an external stimulus or instruction (Frith, Friston, Liddle and Frackowiak, 1991; Jahanshahi, Jenkins, Brown, Marsden, Passingham, et al., 1995; Lau, Rogers, Ramnani and Passingham, 2004). Lesions of the superior frontal gyrus and the ACC render monkeys unable to make self-paced movements even though they are perfectly capable of responding when cued by a tone, and ACC ablation also causes them to be impaired at using reward, but not visual cues, to guide action selection (Hadland, Rushworth, Gaffan and Passingham, 2003; Thaler, Chen, Nixon, Stern and Passingham, 1995).
