The project consists of 4 work modules; nearly all of the objectives have been achieved. A few objectives are still in progress as students complete and defend their PhD dissertations while their research is undergoing review at various scientific journals. All published references have been published in high-impact, peer-reviewed, scientific journals.
Module 1: We created a hierarchically-organized recurrent neural network model of ACC that can implement complex, goal-directed multi-step action sequences. Crucially, the model predicts how hierarchical action sequences are represented at different levels of abstraction along the expanse of ACC. The model was subsequently tested in an fMRI experiment and the results published (Colin et al., 2025). Furthermore, we developed and published a mathematical, formal theory of ACC based on dynamical systems analysis (Holroyd, 2025).
Module 2 and Module3: These modules consist of several fMRI experiments that test the computational framework developed in Module 1. For example, consistent with the model predictions, we showed that ACC monitors reward contingencies to motivate control over hierarchically-organized, goal-directed behaviors (Foinikianaki et al., 2025a). Related studies from these modules have either been published (Shahnazian et al., 2022) or are under review (Alejandro et al., 2025a; Foinikianaki et al., 2025b; Ikink et al., 2025a, 2025b). As just one example, Alejandro et al. (2025b) demonstrated that ACC builds and sustains an abstract representational bridge that links planning to action.
Module 4: We successfully completed two experiments that tested the ACC theory in patient populations. First, by recording brainwave activity from intracranial electrodes placed directly in the brains of 19 patients with epilepsy, we provided the first direct evidence that the ACC is the neural generator of brain-wave component called the reward positivity (Oerlemans et al., 2025). Second, by recording brainwaves from the scalps of 72 stroke patients with lesions to the frontal lobes including ACC, we have shown that damage to ACC disrupts the reward positivity, providing independent, causal confirmation of the results of the intracranial study (Oerlemans et al., under review).
Related: We have published two review articles (Holroyd & Verguts, 2021; Alejandro et al., 2024) and a behavioral study (Wientjes & Holroyd, 2024) related to ACC function.
