Heart rate changes related to risky selections and outcomes in a rat gambling task

Risk-taking behavior is crucial for animals to increase their potential outcomes and is considered to alter arousal states in the brain and body represented by heart rates. In this study, we monitored changes in heart rate as rats performed a gambling task in which they selected either a certain outcome with 100% probability (sure option) or a probabilistic double outcome with 50% probability (risky option). We found that when rats selected risky options, they exhibited significantly greater decreases in their instantaneous heart rates immediately before selection than when they selected certain options. In addition, we observed significantly larger increases in instantaneous heart rates when the rats were informed of the larger number of outcomes after selecting the risky options than after selecting the sure options. These results demonstrate that animals can dynamically alter their instantaneous heart rates in response to risky selection and outcomes.