Magnetoencephalographic neural correlates of capsaicin inhalation-evoked urge-to-cough

Background Vagal sensory neurons that innervate the airways signal the detected noxious information to the brain to produce a perceptible sensation called urge-to-cough as well as reflex and behavioural coughing. Understanding the central neural mechanisms in regulating airway sensory processing is important for the development of more effective therapeutic options for conditions such as chronic cough. Methods In this pilot study, healthy volunteers (n=14) inhaled nebulised capsaicin at a personalised maximum concentration for induction of a strong level of urge-to-cough without coughing. Magnetoencephalography (MEG) was employed to directly detect regional neural activity changes in the brain accompanying capsaicin-evoked urge-to-cough sensations. Results The neural activity in delta and high gamma bands increased with an increase in capsaicin-evoked urge-to-cough in multiple higher order brain regions such as the insula, the cerebellum, the thalamus, the putamen and the brainstem areas, including the medullary nuclei where airway-innervating vagal sensory neurons are known to terminate. Conclusion For the first time, we have established the feasibility and utility of MEG for examining the brain control of coughing. We show that the neural activity in delta and high gamma bands in multiple brain regions including medullary nuclei are involved in processing of urge-to-cough confirming the previous findings with functional MRI.