Studying the neural correlates of upper aerodigestive tract functions under natural conditions: A protocol using functional near-infrared spectroscopy, cervical acoustics, and accelerometry

Background: The upper aerodigestive tract (UADT) is a complex structure with multiple synchronized vital functions, including swallowing and breathing, that rely on central neurological controls and cervical effectors. Reference UADT assessments have questionable limitations in natural conditions. Here, we describe our new protocol addressing these limitations. Our protocol combines three non-invasive technologies to evaluate UADT functions in natural conditions. We aim to correlate the cortical and cervical activities of UADT functions in a real-world context. New method: Healthy subjects perform speech, coughing, throat clearing, and swallowing tasks in a natural sitting position. Cervical evaluation uses acoustic and accelerometric measures that reflect the laryngeal movements and bolus progression. We manually segment the events of each task. Functional near-infrared spectroscopy measures the concurrent cortical activity from the bilateral inferior pericentral regions, including the laryngeal sensorimotor cortices. We statistically compare event signal duration and bolus types under volitional and spontaneous conditions across the three technologies. Comparison with existing methods: Reference UADT evaluations show limitations: cervical assessment references are irradiating (videofluoroscopy) or invasive (flexible nasal laryngoscopy); neurological assessment with functional magnetic resonance imaging (fMRI) does not allow swallowing in sitting position. Expected results and perspectives: We aim to validate this protocol in natural settings and correlate cervical activity with cortical responses. This protocol opens perspectives to investigations on UADT functions in subjects currently with reduced access to gold standards, including children and dysphagic subjects with neurological dystonia. Conclusion: We propose an innovative protocol for UADT evaluation in non-invasive natural conditions.