Environmental contributions to value computations and population dynamics in ventromedial prefrontal cortex
2021-06
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Environmental contributions to value computations and population dynamics in ventromedial prefrontal cortex
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2021-06
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On a hot summer day, there’s nothing nicer than giving a kid on the roadside a dollar in exchange for an ice cold cup of lemonade. That is, unless you just turned down a fifty-cent cup of lemonade. From a traditional perspective, the disappointment you feel when you pay the full dollar for that cup of lemonade is quantifiable: you’ve missed out on an offer that was twice as good as the one you ended up with. However, our brains did not evolve in a world of mathematical equations.The early primate brain had access to no lemonade stands; no dollar values were attributed to its food sources. Instead, early humans then (and other primates now), obtained food a slightly different way: they foraged. Foraging theory is an approach to studying decision making where we assume that because the brain evolved in a naturalistic environment, it is built to make decisions in naturalistic situations. Many foraging studies claim the ventromedial prefrontal cortex (vmPFC)- a brain region strongly associated with value (local) encoding - does not participate in foraging-related (environmental) computations. However, we posit here that the vmPFC contributes to the foraging process by encoding not just local value but also environmental variables.
To this end, we designed a novel diet-search task, for monkeys to complete while we record neural activity in their vmPFC First, we sought out the contribution of local and environmental factors to vmPFC neurons’ processing of value. Specifically, we found relationships between several environmental variables and the animal’s threshold for accepting an offer, as well as encoding in vmPFC in response to the variable. Next, we were interested in examining vmPFC neurons as a population in the same context of foraging-based decision making..Here, we examined how the population of vmpfc neurons moves through stages of the foraging process. Specifically, we determined that distinct computations involving the reward rate occur during travel time versus foraging.
Taken together, our results suggest that when we limit ourselves to only looking at how local value is encoded in the brain, we miss out on a valuable slice of cognition. Ultimately, the power of the foraging framework is that it takes everything that is generally a pesky impediment to clear science - uncontrollable, outside variables - and turns it into an advantage.
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University of Minnesota Ph.D. dissertation. June 2021. Major: Neuroscience. Advisor: Benjamin Hayden. 1 computer file (PDF); iv, 82 pages.
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Mehta, Priyanka. (2021). Environmental contributions to value computations and population dynamics in ventromedial prefrontal cortex. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/224665.
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