Analyzing contextual adaptation in value-encoding neurons during economic choice.

Washington University, Saint Louis MO

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Abstract

? DESCRIPTION (provided by applicant): The proposed research will investigate the dynamics and limitations of contextual adaptation in neurons that encode subjective value. Deficits in economic decision-making characterize a wide range of psychiatric and neurological disorders. The source of these deficits is difficult to determine, in great part because the neural mechanisms behind economic choice remain poorly understood. Several lines of evidence suggest that the orbitofrontal cortex (OFC) plays a key role in economic choice, and particularly in the computation of subjective value. Studies in macaques have identified distinct groups of OFC neurons that encode information about the subjective value of options and outcomes during economic choice. Furthermore, the responses of these neurons appear to adapt depending on the context of the choice. Specifically, these neurons appear to adjust their tuning so that their maximum firing rate always maps to the maximum value the animal has recently seen. In light of these observations, several key questions remain to be addressed. First, while changes in the maximum value trigger adaptation, it is unclear whether changes in the minimum have any effect. The answer to this question could explain known behavioral phenomenon, such as the principle of diminishing marginal utility. Second, it is unclear how quickly value-adaptatio can occur. A slow rate of adaptation could limit subjects' abilities to make decisions effectively n rapidly changing environments. Third, it is unclear whether value-adaptation requires experience of extreme values, or if it can be triggered by abstract information about the values in an environment. If adaptation can be induced by symbolic cues, it would suggest that memory and semantic knowledge can directly manipulate neural representations of subjective value to influence economic choice. I will address these questions in the proposed experiments. I will record from single neurons OFC of macaque monkeys as they choose between juice options, periodically changing the context throughout the session. With the data I obtain, I will determine whether neural responses are affected by changes in the minimum value, measure the rate of adaptation in value-encoding cells, and test whether contextual cues are can induce adaptation before an animal is exposed to extreme values. The results from this project will provide important insight about the flexibility of value representations in the brain. This information wil fill important gaps in our understanding of economic choice circuitry and may ultimately guide the development of more effective treatment options impaired decision-making in patient populations.