Our finding that different populations of ACC neurons represented reward in different states contrasts with studies in rat (Sul et al., 2010) and monkey (Seo and Lee, 2007, 2009) demonstrating that substantially more ACC neurons show a main effect of reward than a reward-choice interaction, indicating that many neurons encoded reward independent of where it was obtained (in these studies choice and reward location were fully confounded). One reason for this difference may be that Sul et al. (2010) recordings in the rat were substantially more rostral than ours. Rodent rostral circulate is more densely interconnected with frontal regions involved in reward processing, including prelimbic, infralimbic, and orbital cortices and amygdala (Fillinger et al., 2017, 2018). However, the recording location in Seo and Lee (2007, 2009) appears broadly homologous with that in our study (van Heukelum et al., 2020). Another possible reason is the tasks used, though as reward location is relevant to future choice in both, it is not obvious why reward representations should be different.
