How the brain resolves conflicts between needs across time
Abstract/Contents
- Abstract
- Animals survive in the world by maintaining the integrity of their bodies. This process, called homeostasis, involves the careful balance of physiological needs. To promote behavior supporting this balance, the brain integrates information about physiological deficits and produces internal states known as drives. These survival drives are powerful sculptors of behavior: a hungry animal will eat; a thirsty animal will drink. What happens when both needs occur, and in similar amounts? In my PhD, I was inspired by an old philosophical quandary of conflicting needs, first stated by Aristotle and later reframed by Spinoza as "Buridan's ass": an equally hungry and thirsty donkey stuck between equidistant food and water. I reasoned that this thought experiment highlights an incomplete behavioral, neural, and conceptual framework relating basic needs to behavior. Is there a singular moment of decision between multiple needs? Where in the brain are such conflicting needs resolved, and how does their resolution relate to the activity of individual neurons? In this dissertation, I will discuss new experimental observations and a computational and conceptual framework for how the brain organizes behavior under multiple concurrent needs. I will first discuss a novel experimental paradigm called Buridan's assay. In it, a hungry, thirsty mouse makes repeated choices between equidistant food and water until it is satiated for both. Using behavioral analysis and optogenetic experiments, I found that choices between conflicting needs are fundamentally stochastic and exhibit periods of persistent behavioral states punctuated by spontaneous switches. To reveal the neural underpinning of this phenomenon, I used high density extracellular electrophysiological recordings to monitor simultaneous activity of many hundreds of neurons across the brain. I found that a substantial population of neurons throughout the brain could predict future choices, and their predictive activity was highly persistent in time. This showed that choices between conflicting needs did not occur at single moments of decision but rather reflected an ongoing goal-like state of the brain. Wanting to understand how this goal-like brain state shifted between hunger-motivated and thirst-motivated goals, I was inspired by a conceptual resemblance between my recorded neural data and the field of non-equilibrium statistical physics. Exploiting mathematical equations and physical insights from thermodynamics, I found, unexpectedly, that a few simple lines of math succinctly explained both behavioral and neural results and successfully predicted new results. This led me to propose a novel framework linking needs to behavior (and resolving "Buridan's ass"), in which needs indirectly and stochastically trap a global goal state into individual need-appropriate contexts. In this framework, shifts between goals emerge spontaneously from collective fluctuations of individual goal-related cells spread across the brain.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2024; ©2024 |
| Publication date | 2024; 2024 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Richman, Ethan |
|---|---|
| Degree supervisor | Deisseroth, Karl |
| Degree supervisor | Luo, Liqun, 1966- |
| Thesis advisor | Deisseroth, Karl |
| Thesis advisor | Luo, Liqun, 1966- |
| Thesis advisor | Druckmann, Shaul |
| Thesis advisor | Giocomo, Lisa |
| Thesis advisor | Shah, Nirao |
| Degree committee member | Druckmann, Shaul |
| Degree committee member | Giocomo, Lisa |
| Degree committee member | Shah, Nirao |
| Associated with | Stanford University, School of Medicine |
| Associated with | Stanford University, Neurosciences Program |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Ethan B. Richman. |
|---|---|
| Note | Submitted to the Neurosciences Program. |
| Thesis | Thesis Ph.D. Stanford University 2024. |
| Location | https://purl.stanford.edu/pb011gr5315 |
Access conditions
- Copyright
- © 2024 by Ethan Richman
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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