Every breath you take, every memory you make

The way you breathe can influence your brain’s ability to form long-term memories, writes Clara Lenherr.

Life and breath are intertwined. Breathing provides your cells with the oxygen they need to survive, but breathing is more than a biological force – it is intricately linked with our state of mind. The connection between breathing and mental state has been acknowledged for thousands of years, with breath being an important tool in spiritual practices such as meditation and yoga.

Breathing is the only involuntary function in our body that can also be consciously controlled, unlike how fast our heart beats or how quickly we digest our food. Yet, how breathing interacts with brain activity remains poorly understood. Recent studies, however, have shown that as we sleep, our respiratory rhythm regulates the transfer of information across the brain to support the consolidation of memories.

The mechanism of breathing relies on an intricate bundle of neurons embedded at the base of our brains, in the medulla. Neurons that fire at a regular pace control the contraction and relaxation of muscles surrounding the lungs to regulate inhalation and exhalation. In turn, air flows through the nose and stimulates sensory neurons that send signals up to the brain, thereby affecting neural activity.

The pathway in charge of our sense of smell overlaps with the emotion centre which is also intertwined with the memory centre in the brain. Could breathing therefore influence our emotions and memory? Nikolaos Karalis and Anton Sirota, both at the Ludwig-Maximilian University in Munich, set out to test this.

The scientists recorded electrical activity in different brain regions and the breathing rate of mice.

While different states of wakefulness affected breathing rate (slower breathing during sleep, for example), the frequency of activity in the prefrontal cortex, at the front of the brain, was found to mirror the frequency of breathing during all states. Thus, breathing continuously modulates brain activity in the region responsible for complex behaviours.

The researchers focused on the poorly understood state of sleep when communication between brain regions via brain waves is abundant. Brain waves are rhythmic patterns of activity generated by groups of neurons that are thought to enable information transfer across the brain.

The majority of neurons fired in sync with the respiratory cycle, usually firing just as the mice breathed in. Having established a relationship between the rhythm of breathing, brain waves, and neuron activity in the prefrontal cortex, they wanted to see if this persisted in other brain regions.

During sleep, memories are thought to be transferred from the hippocampus to long-term storage in the cortex. The authors of the study found that breathing is synchronised with activity between these two brain regions. Although neuroscientists have previously demonstrated a correlation between hippocampal and cortical oscillations, this is the first time that an underlying mechanism has been identified.

The results show that the rhythm of breathing likely coordinates the transfer of information to long-term storage during sleep. Since the integration of new memories into our existing frame of mind influences our sense of self and ultimately our experience of being, the newfound role of breathing rhythm in regulating this process highlights how both our brains and ourselves are synchronised to the rhythm of life.

These important findings provide further support for mechanistic theories of information flow and memory consolidation. While this study focused on the sleep state, the continuous modulation of brain activity by breathing during wakefulness may further modulate perception and emotion processing.

In support of the Yogis and Buddhist practitioners that have long honoured the power of breath as a tool for enhancing our minds, breathing does appear to be an undercurrent beneath the flow of information that encodes our internal state. It will be fascinating to see how a better neuroscientific understanding of this perennial rhythm can be harnessed to modify mental states in the future. Or perhaps the Yogis beat us neuroscientists to it.

Clara Lenherr (she/her) is a neuroscience Master’s student pursuing research into the mechanisms of neural plasticity and computation that underlie learning and memory. (Twitter: @Lenherr_C) She hosts a podcast called Neuroverse available on Spotify, Apple podcasts, and at neuroversecc.wixsite.com/podcast.

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