Abstract
The ACC is implicated in effort exertion and choices based on effort cost, but it is still unclear how it mediates this cost-benefit evaluation. Here, male rats were trained to exert effort for a high-value reward (sucrose pellets) in a progressive ratio lever-pressing task. Trained rats were then tested in two conditions: a no-choice condition where lever-pressing for sucrose was the only available food option, and a choice condition where a low-value reward (lab chow) was freely available as an alternative to pressing for sucrose. Disruption of ACC, via either chemogenetic inhibition or excitation, reduced lever-pressing in the choice, but not in the no-choice, condition. We next looked for value coding cells in ACC during effortful behavior and reward consumption phases during choice and no-choice conditions. For this, we used in vivo miniaturized fluorescence microscopy to reliably track responses of the same cells and compare how ACC neurons respond during the same effortful behavior where there was a choice versus when there was no-choice. We found that lever-press and sucrose-evoked responses were significantly weaker during choice compared with no-choice sessions, which may have rendered them more susceptible to chemogenetic disruption. Together, findings from our interference experiments and neural recordings suggest that a mechanism by which ACC mediates effortful decisions is in the discrimination of the utility of available options. ACC regulates these choices by providing a stable population code for the relative value of different options.SIGNIFICANCE STATEMENT The ACC is implicated in effort-based decision-making. Here, we used chemogenetics and in vivo calcium imaging to explore its mechanism. Rats were trained to lever press for a high-value reward and tested in two conditions: a no-choice condition where lever-pressing for the high-value reward was the only option, and a choice condition where a low-value reward was also available. Inhibition or excitation of ACC reduced effort toward the high-value option, but only in the choice condition. Neural responses in ACC were weaker in the choice compared with the no-choice condition. A mechanism by which ACC regulates effortful decisions is in providing a stable population code for the discrimination of the utility of available options.
Highlights
Real-world decisions rarely involve choosing between unambiguously favorable versus unfavorable options
designer receptors exclusively activated by designer drugs (DREADDs) expression was driven by a CaMKIIa promoter, which is thought to selectively target projection neurons in cortex (Nathanson et al, 2009; Wang et al, 2013)
A separate group of rats was prepared with Gq DREADDs in ACC using identical surgical procedures to the main experiments (Fig. 2A)
Summary
Real-world decisions rarely involve choosing between unambiguously favorable versus unfavorable options. *E.E.H. and G.J.B. contributed to this work as co-first authors. Outside of the striatum, which has been the major region of study in such effort-based decision-making studies We thank members of the A.I. laboratory for helpful comments on a previous version of the manuscript; and Staglin Center for Brain and Behavioral Health for additional support related to fluorescence microscopy
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