The Anterior Cingulate Cortex Directs Exploration of Alternative Strategies

Post by Andrew Vo

What's the science?

Life often throws us curve balls. How we successfully deal with such changes and challenges in our complex environments involves continuous evaluation of our ongoing strategy and switching away to alternative approaches when suitable. The anterior cingulate cortex (ACC) has been implicated in this arbitration between ongoing and alternative strategies, but whether this brain region plays an active role in this process or simply tracks related variables remains unclear. This week in Neuron, Tervo and colleagues demonstrated the role of ACC in strategy arbitration using a foraging task and pathway-specific ACC perturbation in a rodent model.

How did they do it?

The authors trained rats on a foraging task that allowed them to dissociate strategy commitment from strategy re-evaluation. Each trial was initiated at a central nose port, from which rats would decide between two options (levers on the left or right) cued by two auditory tones that were each paired with a distinct probability of receiving a sugar reward (e.g. tone for left lever: 50% probability of reward, tone for right lever: 90%). To either accept or reject the presented option, rats would perform lever presses for possible reward or re-initiate the trial from the central nose port, respectively (see figure). The probabilities of reward for each option changed independently over time

To test the role of the ACC in two distinct computations underlying strategy arbitration, the authors used optogenetics to temporarily “silence” ACC activity either (1) during tone presentation when rats encountered and committed to an encountered option, or (2) after feedback delivery when rats re-evaluated the ongoing strategy. Extracellular recordings of ACC allowed them to observe the selective engagement of ACC during the task. In addition to silencing the entire ACC, the authors also selectively targeted two candidate ACC subcircuits—the intra-telencephalic (IT) and pyramidal tract (PT) pathways—to examine their unique contributions to either option commitment or strategy re-evaluation.

What did they find?

After training, rats were found to strongly prefer one presented option over the other, however, they would continue to occasionally pursue the available non-preferred option throughout the task. These latter trials represented transient switches away from the ongoing strategy towards an alternative. Perturbing ACC activity during option commitment (tone presentation) significantly reduced acceptance of the non-preferred option following unrewarded preferred trials. In contrast, ACC perturbation during strategy re-evaluation (feedback delivery) significantly increased acceptance of the non-preferred option. The authors found that patterns of neuronal activity in the ACC associated with acceptance of preferred versus non-preferred options were distinct and decodable, suggesting ACC is actively involved in the decision-making process.

Optogenetic manipulation of the IT pathway (an ACC subcircuit) during strategy re-evaluation (but not option commitment) increased the probability that rats would accept the non-preferred option following unrewarded preferred trials. In contrast, perturbation of the PT pathway (another ACC subcircuit) during option commitment (but not strategy re-evaluation) reduced the likelihood that rats would accept the non-preferred option. Taken together, these findings demonstrate that the two perturbation effects observed with ACC inhibition at separable time points are mediated by dissociable ACC subcircuits.

What's the impact?

In summary, this study demonstrates that ACC plays an active role in strategy switching. Computations involving strategy re-evaluation versus commitment to pursue an alternative option were shown to be anatomically and functionally dissociable. Critically, the authors offer causal evidence of this role by using targeted optogenetic perturbations during distinct time points and within specific ACC pathways.

Tervo et al. The anterior cingulate cortex directs exploration of alternative strategies. Neuron (2021). Access the original scientific publication here.