The Role of the Anterior Cingulate Cortex in Effort-Based Decision Making
Post by Lincoln Tracy
What's the science?
Decision making often requires comparing possible options, such as the amount of effort required to be exerted to achieve the desired outcome. The anterior cingulate cortex (ACC) is a part of our brains that plays a role in weighing up the costs of different options prior to making a decision. However, it is not clear how the ACC mediates these cost-benefit evaluations. This week in The Journal of Neuroscience, Hart and colleagues used chemogenetics and calcium imaging to determine the mechanism underlying the role of the ACC in effort-based decision making.
How did they do it?
Male rats were trained to exert effort to receive a reward (sucrose pellets) in a lever-pressing task that progressively became more difficult. In the initial stages, one lever press earned a single sucrose pellet, but in later stages, the required number of lever presses for each subsequent pellet increased. After completing the training, the rats were tested under two different conditions. The first was a ‘no-choice’ condition, where rats could only receive sucrose pellets after pressing a lever. The second condition involved choosing between two food options—pressing a lever to receive a sucrose pellet or taking standard rat chow from a small bowl. Prior to testing, the authors injected either inhibitory or excitatory Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) into the ACC via a surgically-inserted cannula to alter its activity. They examined the number of times the rats pressed the levers in each condition to determine their food preferences. The authors also implanted calcium imaging recording equipment into the rats’ brains to compare the activity of the ACC cells during the choice and ‘no choice’ tasks.
What did they find?
Rats made more lever presses during the ‘no choice’ condition compared to the choice condition, where standard chow was freely available from a bowl. Rats injected with DREADDs that either excited or inhibited ACC activity made fewer lever presses during the choice condition, but not the ‘no choice’ condition. Lever pressing patterns did not differ during the ‘no choice’ condition. Therefore, the authors concluded that ACC interference disrupted high-effort lever-pressing behavior when there is a choice of two food options available. Calcium imaging revealed that pre-lever pressing cell activity was greater during the ‘no choice’ condition, compared to the choice condition. That is, ACC neurons were less responsive prior to the onset of lever pressing when the rats had a choice of taking chow from the bowl or pressing the lever for a sucrose pellet. The neurons were also less responsive when rats collected the reward when they had a choice of lever pressing vs. chow.
What's the impact?
This was the first study to examine the role of the ACC in a cell-specific and temporally restricted manner. Taken together, the findings suggest that the ACC regulates effort-based decision making by providing a stable population code to discriminate between the usefulness of the available options. Further study into the contributions of the ACC in effort-based choices may enhance our understanding of the motivational mechanisms in disorders such as depression and addiction.
Hart et al. Chemogenetic modulation and single-photon calcium imaging in anterior cingulate cortex reveal a mechanism for effort-based decisions. Journal of Neuroscience (2020). Access the original scientific publication here.