Summary: A new study of decision-making in mice reveals that choice is not a single moment but a reflection of the brain’s pre-existing state.
The research, using the Buridan test, suggests that the brains of mice constantly broadcast their goal, even before options are available, with patterns of neural activity predicting choice.
Hunger and thirst do not directly determine behavior; instead, they modulate the brain’s goal setting, with a random element causing changes between needs, ensuring that both are satisfied over time.
- Hunger and thirst indirectly modulate the mice’s behavior, affecting the brain’s goal rather than directly motivating choice.
- Patterns of neural activity in the brain can predict a mouse’s choice before it is even presented with options, indicating constant diffusion of the brain’s current goal.
- Chance plays a key role in decision-making, with mice often repeating their choices before abruptly changing, ensuring that their hunger and thirst needs will ultimately be met.
Making decisions is difficult. Even when we know what we want, our choice often leaves something else on the table. For a hungry mouse, every morsel counts. But what if the decision was more consequential than choosing between crumbs and cheese?
Stanford researchers studied how mice resolve conflicts between basic needs in a study published in Nature on November 8. They presented mice that were both hungry and thirsty with equal access to food and water and observed what happened next.
The mice’s behavior surprised scientists. Some turned to water first, while others chose food. Then, with seemingly “random” periods of indulgence, they alternated.
In their study, doctoral student Ethan Richman, lead author of the paper, and colleagues in the departments of biology, psychiatry and behavioral sciences, and bioengineering, explored why.
This work builds on years of collaboration between co-senior authors Karl Deisseroth, DH Chen Professor at Stanford Medicine, and Liqun Luo, Ann and Bill Swindells Professor in the School of Humanities and Sciences, to understand how the brain keeps the body alive. .
What is Buridan?
“There’s this old philosophical dilemma called Buridan’s Ass,” Richman explained, “where you have a donkey who is equally hungry and thirsty and equally far from food and water.”
The concept was posed by the philosophers Aristotle, Jean Buridan and Baruch Spinoza, in different forms. The question was whether the donkey would choose one need over another or whether he would stubbornly stay in the middle.
But animals constantly make choices. We must satisfy our needs to maintain homeostasis. Richman and his colleagues wanted to know how the brain directs traffic through conflicting signals to bypass Buridan. They call their behavioral experiment the Buridan Test.
If hunger or thirst directly motivated a mouse to eat or drink, it would change whenever one need outweighed the other. When the needs were equal, the mouse remained stuck. This is not what the researchers observed.
“Our data indicate that thirst and hunger do not act as direct forces on behavior,” Richman said. “Instead, they modulate behavior in more indirect ways. They influence what we consider to be the current goal of the mouse.
The purpose of a mouse
We often think of choices as a defining moment. The researchers wanted to understand when and where choices between food and water arise in the brain. Using recent advances in recording technology, they monitored the activity of individual neurons distributed throughout the mouse brain.
To their surprise, patterns of neuronal activity throughout the brain predicted the mouse’s choice, even before it was presented with options.
“Instead of a single moment of choice, the mouse brain constantly broadcasts its current goal,” Richman said.
“The results of the most difficult choices you make – when the options are closely balanced in importance, but the categories are fundamentally different – may have to do with the state your brain was in, even before the choice was made. be presented,” Deisseroth said.
“This is an interesting result and helps us better understand certain aspects of human behavior.”
Researchers have found that hungry and thirsty mice often make the same choice repeatedly before suddenly switching.
“In feeding mode, the mouse will just eat and eat. In drinking mode, he will drink and drink,” Luo said.
“But there is a random aspect that causes them to switch between the two. This way, in the long run, they satisfy both needs, even if they only choose one at any given time.
To test this seemingly randomness, the researchers conducted another experiment, this time with starving mice. While the mice ate, the scientists introduced thirst using a technique called optogenetics.
With optogenetics, they used light to activate thirst-causing neurons. Sometimes the mice would turn to the water, and sometimes they would ignore it and continue eating. The thirst level was the same each time, leading the researchers to conclude that there is a key random element influencing the mouse’s goal.
Scientists were perplexed by the interaction between this randomness and the relative intensities of hunger and thirst. To understand it better, they turned to mathematical modeling. Inspired by a conceptual resemblance between their results and a distant area of physics, the researchers borrowed, tweaked and simulated several equations.
“We were extremely surprised and excited to find that a few simple equations from a seemingly unrelated discipline could closely predict aspects of mouse behavior and brain activity,” Richman said.
Their modeling results suggest that mouse goal-related brain activity is constantly in motion. He is trapped by needs like hunger and thirst. To escape and move from one objective to another, the mouse relies on a series of random activities.
This work establishes the importance of changing the brain’s baseline state when it comes to decision-making. In the future, researchers will explore what sets the tone and why decisions don’t always make sense.
“Regarding Buridan’s donkey, we can say that the donkey’s decision is made before it is given a choice,” explains Richman, “and if it has to wait, then its choice can change spontaneously .” The clinical applications of this work in the human context are a little more complex.
“As a psychiatrist, I often think about how we make healthy (adaptive) or harmful (maladaptive) decisions,” Deisseroth said. (Maladaptive behaviors impact people’s ability to make decisions in their best interests and are common in psychiatric disorders.)
“It is very difficult for family and friends to see their loved ones acting against their own urges to survive. This can help understand that the choices made reflect the underlying dynamic landscape of the patient’s brain, affected by the disorder more than by the patient’s conscious will.
While this work may not explain human behavior, it begins to reveal an important framework for decision-making. “This is a fundamental scientific discovery that depends on some pretty advanced neuroengineering, but we’re essentially addressing universal questions that people think about and grapple with all the time,” Deisseroth said.
“It’s exciting to develop and apply modern tools to answer these very old, deep and personal questions.” »
Other Stanford co-authors include former undergraduate student Nicole Ticea, BS ’20, who is now a doctoral student at Stanford, and former graduate student William E. Allen, PhD ’19, who is now at the Harvard University.
Deisseroth is also a professor of bioengineering, psychiatry and behavioral sciences, and a member of Stanford Bio-X and the Wu Tsai Neurosciences Institute.
Luo is also a professor of biology, a faculty member at Sarafan ChEM-H, and a member of Stanford Bio-X, the Stanford Cancer Institute, and the Wu Tsai Neurosciences Institute. Both Deisseroth and Luo are investigators at the Howard Hughes Medical Institute.
Funding: This work was funded by the National Science Foundation, the National Institutes of Health, and the Gatsby Foundation.
About this decision-making news and research in neuroscience
Author: Taylor Kubota
Contact: Taylor Kubota – Stanford
Picture: Image is credited to Neuroscience News
Original research: Free access.
“Neural landscape diffusion resolves conflicts between needs over time” by Ethan Richman et al. Nature
Neural landscape diffusion resolves conflicts between needs over time
Animals engage in flexible, goal-directed behaviors to satisfy their basic physiological needs. However, little is known about how unitary behaviors are chosen in the face of conflicting needs.
Here we reveal the principles by which the brain resolves these conflicts between needs over time.
We developed an experimental paradigm in which a hungry and thirsty mouse has a free choice between food and water at an equal distance. We found that mice collect rewards tailored to their needs by structuring their choices into persistent periods with stochastic transitions.
High-density electrophysiological recordings during this behavior revealed distributed correlates between single neurons and neuronal populations of a persistent internal goal state guiding the mouse’s future choices. We captured these phenomena with a mathematical model describing a global state of need that is noisily diffusing across an evolving energy landscape.
Model simulations successfully predicted behavioral and neural data, including neuronal population dynamics before choice transitions and in response to optogenetic stimulation of thirst.
These findings provide a general framework for resolving need conflicts over time, rooted in the emergent properties of need-dependent state persistence and noise-induced shifts between behavioral goals.