These tasks, while conceptually appealingly simple, contain several different factors which could be driving the ACC activation. One possibility is that the response in this region is being driven by detecting when an incorrect response has been made (Holroyd and Coles, 2002) or that the likelihood of making an error is high (Brown and Braver, 2005). A related concept is that the ACC might instead be concerned with monitoring for times of response conflict, which is likely to be at its greatest at the time of a switch as people try to inhibit the previously correct response in order to select the now appropriate one (Botvinick, Braver, Barch, Carter and Cohen, 2001; Botvinick, Cohen and Carter, 2004). Both of these theories imply that the ACC does not itself directly regulate response selection but instead signals to interconnected regions such as the lateral prefrontal cortex a need to exert control or modify behaviour.
