Conflict over Cingulate Cortex: Between-Species Differences in Cingulate May Support Enhanced Cognitive Flexibility in Humans

ods used in human and monkey studies is highly desirable, we maintain that the most plausible explanation of observed interspecies differences lies elsewhere. One plausible account is that conflict-related ACC activity reflects processes within the region, such as competition among groups of interneurons, that are better detected by fMRI (more often used in human studies) than single-unit activity recording (more often used in monkey studies). On this point, which Schall and Emeric do not challenge, we note that fMRI has been shown to be sensitive to a wider range of activity in other regions as well, such as in the frontal eye fields [Ford et al., 2009]. An alternative possibility is that only humans have a functional region in the dorso-caudal portion of the ACC that is sensitive to conflict. Strong anatomical evidence suggests that humans have a unique region (area 32 ) that may provide this function [Vogt et al., 1995]. Schall and Emeric argue that this same evidence suggests a homologous area 32 in monkeys and humans. However, this was not the conclusion of the authors of the studies in question, nor of Brodmann himself when he labeled those areas with the same numSchall and Emeric [2010] provide a thoughtful commentary on our recent review of the discrepancies between functions attributed to the macaque monkey and the human anterior cingulate cortex (ACC) [Cole et al., 2009]. We agree with Schall and Emeric on many points. Indeed, our review considered the main point discussed in their commentary: the notion that effector differences might account for interspecies discrepancies because relevant studies have typically used saccades for monkeys versus forelimb movements for humans. However, it is important to note, as we did in our paper, that two key studies challenge this argument. Both Curtis et al. [2005] (in humans) and Ford et al. [2009] (in monkeys) reported conflict-related fMRI activity in the ACC during saccade tasks, demonstrating that this region shows conflict sensitivity even when the task involves the same response modality as typical monkey studies. Together, these two studies challenge any straightforward account of interspecies discrepancies in terms of effector differences. Thus, although we agree with Schall and Emeric that closer integration of methPublished online: August 6, 2010