Listen Up: Auditory Attention May Rely on Your Vagus Nerve
Diaphragmatic breathing may improve auditory processing via the vagus nerve.
Posted Jun 10, 2019
Last month, I reported on a growing body of evidence showing that longer exhalations are an easy way to hack your vagus nerve, reduce fight-flight-or-freeze stress responses, and improve heart rate variability (HRV). Higher HRV is linked to more robust vagus nerve activity, which triggers the "relaxation response."
That post was inspired by a recent study (De Couck et al., 2019) which found that just two minutes of slow, diaphragmatic breathing stimulated the vagus nerve, increased HRV, and helped people make better decisions. As the authors summed up, "These [findings] show that brief vagal breathing patterns reliably increase HRV and improve decision-making." (Vagal means "relating to the vagus nerve.")
Yesterday, I learned about another new study (de Góes et al., 2019) which advances our understanding of how hacking the vagus nerve might improve auditory attention and boost information processing in the brain. This paper, "Interaction Between Cortical Auditory Processing and Vagal Regulation of Heart Rate in Language Tasks: A Randomized, Prospective, Observational, Analytical and Cross-Sectional Study," was recently published in the journal Scientific Reports.
This study was conducted by an international team of researchers from São Paulo State University in Brazil along with colleagues at Oxford Brookes University in the United Kingdom. Senior author, Vitor Engrácia Valenti, is a professor in the Department of Speech and Hearing Pathology at São Paulo State University and was the principal investigator for this study.
The study's findings suggest that stress-induced changes in the autonomic nervous system trigger variations in heart rate that are associated with subpar auditory attention and perception.
"This suggests that auditory information is processed less well in stressful than calm situations," Valenti said in a statement. "It's possible that if you breathe more slowly under stress, for example, the parasympathetic nervous system may slow your heart rate and improve your auditory perception."
In extreme cases of high anxiety (e.g., panic attacks), the researchers speculate that impaired auditory attention may be directly linked to unbridled fight-or-flight stress responses. As the authors explain, "We advocate that the interaction between parasympathetic regulation of heart rate and cortical auditory processing is involved in this physiological response."
"Previous studies with animals showed that vagal activity increases during relaxing auditory stimulation and boosts the expression of a protein called c-Fos in the auditory cortex. These findings pointed to an association between cortical sound processing and the parasympathetic nervous system," Valenti said. "However, exactly how auditory stimuli influence heart rate control by the vagus nerve was poorly understood. In addition, it wasn't clear whether heart rate control interacted with the cortical brain activity associated with auditory attention in humans."
To explore this phenomenon further, Valenti and his team recruited 49 study participants who each took a stress-inducing language test. During this language task, participants were asked to say as many words beginning with the letter "A" as possible in one minute without any repetition. HRV was measured throughout the language test as an indicator of autonomic cardiac responses to different stress levels.
Auditory processing was also measured immediately before and after the mildly stressful language task. Additionally, an electrophysiological procedure called "long-latency auditory evoked potential (P300)" was used to assess the integrity of the auditory pathway in the brain. According to the researchers, the P300 can "analyze auditory attention to a sound stimulus by monitoring the prefrontal cortex and auditory cortex activity via electrodes placed on the forehead, cranial vertex, and earlobes."
The findings of their investigation suggest that the stress response triggered by the language challenge activated the sympathetic nervous system and accelerated heart rate, which was associated with reduced auditory attention. Their statistical analysis showed a significant correlation between autonomic control of heart rate via the vagus nerve and better auditory perception.
"The findings suggest novel possibilities for the treatment of patients with attention and communication disorders based on vagus nerve activation by electrical stimulation in the auricular region to control heart rate," Valenti concluded.
Viviane B. de Góes, Ana Claúdia F. Frizzo, Fernando R. Oliveira, David M. Garner, Rodrigo D. Raimundo, and Vitor E. Valenti. "Interaction Between Cortical Auditory Processing and Vagal Regulation of Heart Rate in Language Tasks: A Randomized, Prospective, Observational, Analytical and Cross-Sectional Study." Scientific Reports (First published: March 12, 2019) DOI: 10.1038/s41598-019-41014-6
Marijke De Couck, Ralf Caers, Liza Musch, Johanna Fliegauf, Antonio Giangreco, and Yori Gidron. "How Breathing Can Help You Make Better Decisions: Two Studies on the Effects of Breathing Patterns on Heart Rate Variability and Decision-Making in Business Cases." International Journal of Psychophysiology (First published: March 1, 2019) DOI: 10.1016/j.ijpsycho.2019.02.011