Study shows how respiratory rhythm shapes memory processes

First and foremost, we breathe in order to absorb oxygen - but this vital rhythm could also have other functions. Over the past few years, a range of studies have shown that respiration influences neural processes, including the processing of stimuli and memory processes. LMU researchers led by Dr. Thomas Schreiner, leader of an Emmy Noether junior research group at the Department of Psychology, in collaboration with colleagues from the Max Planck Institute for Human Development in Berlin and the University of Oxford, have analyzed how respiration influences the retrieval of previously learned materials and recorded what happens in the brain during this process.

For the experiment, 18 participants learned to associate 120 images with certain words. The participants were then asked to recall these associations, and then asked to recall them again after a two-hour afternoon nap. While this was happening, the researchers recorded their breathing as well as their brain activity via EEG.

Respiratory rhythm helps with multi-stage remembering process

Now published in The Journal of Neuroscience, the study results show that the participants were better able to recall the words and the corresponding images when the reminder cues were presented during or just before inhalation. "In the EEG, it becomes apparent, however, that the actual memory retrieval tends to happen during subsequent exhalation," reports Schreiner. "Our data thus points to a sort of functional bifurcation: Inhalation is a favorable moment to receive the reminder cue, while exhalation is a favorable moment for the actual reconstruction of the memory in the brain." This shows that respiratory rhythm shapes the temporal interplay of perception and effective remembering.

In the EEG recordings, the researchers found two characteristic signatures of successful remembering, which offer insights into the underlying neural patterns: One was the weakening of certain brainwaves - more specifically, alpha and beta activity. This suggests that the brain might activate a memory and focus more strongly on retrieval. The second signature consisted of so-called memory reactivations. In successful remembering, the same neural patterns resurfaced here as were active during learning.

In the experiment, the participants concentrated wholly on the memory task while maintaining their natural respiratory rhythm. "To find out whether useful everyday strategies can be derived from our findings, we would need studies with targeted respiratory manipulation," says first author Esteban Bullón Tarrasó. He also notes the need for more research into older memories. "However, the underlying mechanisms suggest that respiration also plays a role there."

Individual variations can exist in the extent to which memory-relevant brain processes are synchronized with respiration. The researchers found differences in degree between the participants, from which they conclude that respiration is linked more efficiently to neural processes in some people than in others. And if brain and respiration interact better, then presumably remembering works better accordingly: "Respiration is a natural pacemaker for memory processes, highlighting how closely our bodies and brains interact."