Neuroscience study reveals how breathing shapes brain activity during anxiety

A recent study published in The Journal of Neuroscience has found evidence for a link between breathing patterns and brain activity during anxious states. Researchers found that rats experiencing anxiety-like behavior in a common behavioral test breathed more rapidly and that this change in breathing influenced brain rhythms in a key frontal brain area. The study highlights how shifts in respiration actively shape how the brain functions during emotional experiences.

Scientists have long known that feelings of anxiety can trigger physical changes in the body, including alterations in breathing. Previous research has shown that breathing influences brain activity, particularly in areas involved in processing smells and in the front part of the brain. This connection between breathing and brain function has been especially well-documented in relation to fear, where slow, steady breathing is often linked to freezing behavior in rodents. However, it remained unclear whether breathing plays a similar role in other negative emotional states like anxiety, which tends to involve faster breathing.

To investigate this, researchers set out to understand how breathing affects brain activity in situations that evoke anxiety. They used a widely accepted method for studying anxiety in rodents called the elevated plus maze. This maze is shaped like a plus sign and has two arms that are enclosed and two that are open and exposed. Because rats naturally prefer the safety of enclosed spaces, spending time in the open arms is considered an indication of anxiety-like behavior.

During the experiment, the scientists placed rats in the elevated plus maze and allowed them to explore freely for ten minutes. At the same time, they recorded two key types of data: the rats’ breathing patterns and the electrical activity in two brain regions—the olfactory bulb, which is involved in smell and also transmits breathing-related signals, and the medial prefrontal cortex, a part of the brain involved in regulating emotions and decision-making.

To measure breathing, the researchers inserted a small, curved tube into the nasal cavity, which was connected to a pressure sensor that could detect airflow with each breath. For brain activity, they surgically implanted tiny electrodes in the olfactory bulb and prefrontal cortex to measure electrical signals generated by neurons. The rats were also filmed from above to track their movements and determine whether they were in the open arms, closed arms, or central area of the maze.

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The researchers then analyzed the data and uncovered several striking patterns. First, they found that the rats’ breathing rate varied depending on where they were in the maze. When the animals were in the closed arms—the safer, enclosed sections—their breathing was relatively slow, typically in the range of 0.5 to 4 breaths per second (hertz). In contrast, when they explored the open arms or the central platform, their breathing sped up to between 5 and 10 hertz.

While faster breathing can be associated with increased movement, the team showed that even when the rats moved at similar speeds, they still breathed more rapidly in the open areas. This indicates that the breathing changes were related to emotional state rather than physical activity alone.

Next, the team examined the electrical signals recorded from the brain. They found that both the olfactory bulb and the prefrontal cortex showed brain waves that were tightly synchronized with the animals’ breathing rhythm. These patterns, known as respiration-coupled oscillations, occurred at the same frequency as the rats’ breathing and changed depending on whether the rats were breathing slowly or quickly. This revealed that the brain was not only tracking the act of breathing, but actually reflecting its timing in ongoing electrical activity.

Most notably, these breathing-related brain waves were stronger when the rats were in the open arms and experiencing anxiety-like behavior. The synchronization between breathing and brain activity became more prominent during fast breathing states, suggesting that the influence of respiration on the brain intensifies during anxiety.

To confirm that nasal airflow was driving these brain rhythms, and not the other way around, the researchers used a statistical method called Granger causality. Their analysis showed that the timing of nasal breathing predicted the timing of brain activity, indicating that sensory input from the airflow itself was shaping neural activity in both the olfactory bulb and prefrontal cortex.

The study also explored how breathing affects a particular type of fast brain wave known as gamma oscillations, which are associated with attention, working memory, and sensory processing. The researchers found that the phase of each breath cycle modulated the strength of gamma activity in the prefrontal cortex.

Importantly, this effect changed depending on the rats’ emotional state. When the rats were in the closed arms and breathing more slowly, gamma activity around 85 hertz was influenced by the slower breathing rhythm. But during anxious periods in the open arms, the faster breathing rhythm modulated a slightly faster gamma frequency, around 100 hertz. This suggests that not only does breathing shape the timing of brain activity, it can also shift the type of gamma waves present in emotionally relevant brain regions, potentially influencing how information is processed under stress.

The researchers note several limitations of their work. Since the study was conducted in rats, it remains to be seen whether the same patterns apply to the human brain. The recordings were limited to the olfactory bulb and prefrontal cortex, so future studies could explore whether other brain regions involved in emotion, such as the amygdala or hippocampus, show similar respiration-linked activity.

Additionally, while the study demonstrates a strong relationship between breathing and brain rhythms during anxiety, it does not fully explain how breathing shapes the activity of individual brain cells. Further research is needed to uncover the exact pathways through which breathing influences emotional behavior.

Nevertheless, the findings add to a growing body of research showing that breathing rhythms are tightly connected to brain function, particularly in areas involved in emotion and decision-making. They also underscore the importance of nasal airflow itself in this process, as the brain appears to respond to the physical sensation of breathing in through the nose. While these experiments were conducted in rats, they have important implications for understanding anxiety in humans.

Breathing-based therapies, such as slow breathing exercises or mindfulness practices, are already known to reduce anxiety in people. This study provides a biological explanation for why these techniques might work: altering breathing patterns could directly influence the neural circuits involved in emotional processing.

The study, “Breathing Modulates Network Activity in Frontal Brain Regions during Anxiety,” was authored by Ana L. A. Dias, Davi Drieskens, Joseph A. Belo, Elis H. Duarte, Diego A. Laplagne, and Adriano B. L. Tort.