Conflict neurons in cingulate cortex of macaques

Conflict—the magnitude of co-activation of mutually incompatible response processes—was proposed to explain how cognitive control is invoked (Botvinick et al. 2001) and continues to engage debate (Becker et al. 2024). Original observations consistent with this construct emphasized the primary contribution of cingulate cortex (CC) based on human functional imaging (Botvinick et al., 1999; Carter et al., 2000) and electroencephalogram (Yeung, Botvinick, & Cohen, 2004). In countermanding tasks conflict arises through co-activation of competing GO and STOP processes (Boucher et al. 2007; Schall & Boucher 2007; Sajad et al. 2022). Single neuron activity representing conflict has been described in the supplementary motor cortex of human epilepsy patients (Fu et al., 2019; Sheth et al., 2012) and of macaque monkeys (Sajad, Errington, & Schall, 2022; Stuphorn, Taylor, & Schall, 2000) and in human cingulate cortex (Fu et al., 2019; Sheth et al., 2012) but not in monkey cingulate cortex (Ebitz & Platt, 2015; Ito, Stuphorn, Brown, & Schall, 2003; Nakamura, Roesch, & Olson, 2005). This lack of homology generated debate about the utility of macaques for investigation of cognitive control (Cole et al. 2009; Schall & Emeric 2010). With higher-resolution, less-biased samples, we re-examined the presence of a conflict signal in cingulate cortex of monkeys. Neurons modulating specifically when response conflict was maximal were found in cingulate cortex— more commonly in the dorsal than the ventral bank. However, such neurons were much more common in supplementary motor cortex. These data confirm the presence of a conflict signal in medial frontal cortex and demonstrate that it can be found in a small fraction of neurons in cingulate cortex. Further research is needed to determine if the weak response conflict signal in cingulate cortex is sufficient or negligible.