How our brains tell us when we need to eat or drink

The brain plays a central role in guiding us to eat or drink, even when we’re not consciously thinking about it. Most of us reach for a snack or a glass of water without much thought, but behind the scenes, the brain is working hard.

A complex system of signals, cells, and communication networks helps us stay fueled and hydrated. Still, scientists are only beginning to understand how the brain figures out what the body needs — and when.

New research from the Max Planck Institute for Biological Intelligence, working with the University of Regensburg and Stanford University, shines a light on a specific part of the brain that may be responsible for pushing us to eat or drink.

The team studied mice and found that certain groups of neurons in the amygdala – the part of the brain that helps process emotions and motivation – play a crucial role in managing hunger and thirst.

Brain links emotion with thirst and hunger

The amygdala is often tied to emotions like fear, pleasure, and decision-making. But it turns out that it also affects how much and when we eat and drink.

Earlier studies from this team showed that neurons in the amygdala link food to emotional experiences.

Pleasant meals are linked with joy. Nausea reduces appetite. Even an unpleasant meal can build an aversion that sticks.

In those earlier experiments, researchers found they could influence mice behavior by adjusting neuron activity.

The mice would start eating, even if they were already full or feeling sick, based on how these neurons were manipulated.

Hunger and thirst on separate tracks

This latest study takes things further. It shows that different sets of neurons in the amygdala respond specifically to either thirst or hunger.

“One of these groups of neurons is solely dedicated to regulating the desire to drink, the first ‘thirst neuron’ that has been identified in the amygdala,” explains Federica Fermani, who led the study.

“When we activated these neurons, the mice drank more, and when we suppressed their activity, the mice drank less. We also identified another group of neurons in the same region of the amygdala that drives thirst but also plays a role in regulating hunger.”

These findings highlight how some neurons show remarkable specialization for specific behaviors, while others have more general roles in guiding food and drink choices.

To observe this, the researchers used tools like optogenetics – a method that uses light to control brain cells. This allowed them to precisely turn certain neurons on or off.

They watched how the mice behaved when thirsty, hungry, or already satisfied. With these tools, they mapped out where these neurons receive their cues and which other parts of the brain they talk to.

Neurons influence taste perception

Interestingly, the team also learned that these neurons could influence taste preferences.

By linking the activation of certain neurons with a drink the mice didn’t like, they managed to change the animals’ behavior.

A flavor that had been avoided became one the mice started to choose.

This ability to alter choices with neuron signals gives scientists a new way to look at how emotions, desires, and past experiences shape what we choose to eat and drink.

Since the structure of the amygdala is similar in humans and mice, the research may help explain human eating patterns too.

“Basic drives like thirst and hunger ensure we eat and drink at the right times, giving our bodies the hydration and nutrition needed to survive,” explains Rüdiger Klein, Director at the Max Planck Institute for Biological Intelligence.

“But these same neural circuits can also contribute to overeating or undereating, depending on the signals they encounter in the brain.”

Hunger, thirst, and the human brain

By uncovering these processes, we gain a better understanding of how the brain emotionally evaluates food and drink, learns to associate them with pleasure or aversion, and how neural development shapes both innate and learned behaviors.

This research raises important questions about how the brain balances multiple needs.

How does it know when we’ve had enough? What happens when hunger and thirst compete? And how do these systems become disrupted in conditions like obesity, anorexia, or addiction?

As scientists continue to untangle the connections between emotion, memory, and behavior in the brain, studies like this offer a clearer picture of how we make some of our most basic – and most important – choices every day.

The full study was published in the journal Nature Communications.

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