ORCID

http://orcid.org/0000-0002-4068-1168

Date of Award

Winter 12-15-2021

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Neurosciences)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Economic choices entail two mental processes, value calculation and value comparison (Niehans, 1990). Studies in the last twenty years have shown that neurons in the orbitofrontal cortex (OFC) could support both processes. Namely, in the studies in which monkeys chose between two juice options with various amounts, three functional cell groups had been found in the OFC: offer value cells encode the value of individual juices, chosen juice cells encode the choice in a binary way and chosen value cells encode the value of the chosen juice (Padoa-Schioppa and Assad, 2006). These results suggest a decision circuit within OFC with offer value cells encoding the input and chosen juice cells encoding the output (Padoa-Schioppa, 2011). However, this proposal remains tentative. If OFC is crucial to the economic choices, neural activities in the OFC should 1) causally relate to the decisions and 2) explain the behavioral variabilities. Therefore, in my dissertation studies, I aim to examine these two aspects. In the first study, we use electrical stimulation to establish the causal link between neuronal activity in the OFC and the economic choices. We find that low current micro-stimulation increases the encoded values and facilitates the choices by inducing a range-dependent bias. On the other hand, high current micro-stimulation disrupts both the valuation and comparison stages, and affects the order bias under sequential offer and reduces the choice accuracy. In the second study, we focus on the neural correlates with behavioral biases under sequential offers. We train the monkeys to perform a task in which trials from simultaneous offers and sequential offers are randomly interleaved. We first confirm that the same neural circuit mechanism is adopted under simultaneous offers and sequential offers. This result provides the basis to examine the neural correlates using a unified decision model we proposed based on simultaneous offers. We then compare the behavioral patterns of simultaneous offers and sequential offers. We find that sequential offers show lower choice accuracy, bias in favor of the preferred juice (preference bias) and bias in favor of the second offer (order bias). Neural correlates of each of the biases reveal that low choice accuracy partly reflects the weaker value signals in sequential offers, order bias is correlated with comparison signals and preference bias emerges late in the comparison stage. Taken together, my dissertation studies fill in some important gaps between the neuronal activity of the OFC and the economic choices.

Language

English (en)

Chair and Committee

Camillo Padoa-Schioppa

Committee Members

Camillo Padoa-Schioppa

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