Using the laryngeal adductor reflex to investigate swallowing

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The goal of this study was to develop a protocol to facilitate identification and quantification of the pathological components of the complex neural swallow circuit in mice, the model organism identified by the NIH for studying human neurological diseases. Investigating the relatively simple neural circuit of the laryngeal adductor reflex (LAR) in mice may help elucidate the underlying pathology contributing to dysphagia in neurological diseases. Ninety-eight healthy mice between 3-6 months of age underwent a surgical procedure to trigger the LAR while recording associated laryngeal brainstem evoked potential responses (LBR) via subcutaneous needle electrodes. A 2.0 Hz electrical stimulus was directly applied to the superior laryngeal nerve (SLN) at various intensities to evoke the LAR. LBR waveforms were extracted from background EEG using traditional signal averaging. Several positive and negative peaks were detected within 10 ms after SLN stimulation. Quantification of response peaks relative to amplitude and latency will provide normative data for comparison with mouse models of human diseases. The neurological components recruited during LAR are also recruited during swallowing; however, the swallow reflex is more complex and involves additional brain regions. Therefore, the LAR may provide a simplified window into the investigation of swallowing and may ultimately translate into noninvasive clinical methods for use with humans with dysphagia as a consequence of neurological diseases such as amyotrophic lateral sclerosis (ALS).