Motor strategy in rapid sequential swallowing: New insights

This study examined the physiological properties and movement strategies of normal, rapid sequential swallowing during simultaneous videofluoroscopy ( VFS) and submental surface electromyography (EMG). Ten subjects performed d iscrete (5 and 15 cc) and sequential (150 cc in tilted and upright head pos tures) swallowing tasks. Analyses included VFS event timing, movement/bolus passage characteristics, EMG amplitude waveforms, and peak and offset EMG amplitudes. Results revealed that sequential swallows were significantly sh orter than discrete swallows in several VFS event durations, but significan tly longer in pharynaeal transit and stage transition times. The hyolarynge al system exhibited a cyclical "rise and partial fall" movement pattern dur ing sequential swallows on VFS, corresponding to a repetitive "activation a nd partial deactivation" characteristic on EMG. Greater peak EMG amplitude for sequential than discrete swallows was found in 6/10 subjects. Pharyngea l bolus merging, preparatory laryngeal gestures, and penetration without as piration were also observed in some subjects on VFS. Intersubject differenc es were significant in timing measures and EMG amplitude. Our Findings of i ndividual variability and subject-specific strategies for task accommodatio n support the notion of built-in plasticity in the deglutitive motor comple x.