Cortical Control Mechanisms in Volitional Swallowing: The Bereitschaftspotential

Objective: This research sought to identify a well-defined pre-motor potential, the Bereitschaftspotential (BP), as a manifestation of cortical contribution to the pre-motor planning of volitional swallowing. Methods: EEG data were collected from 20 research participants during volitional execution of swallowing and finger movement tasks. A 5 second pre-movement epoch for each task was triggered on EMG identification of movement onset. A grand average for each task representing approximately 2400 trials across all research participants was derived to compare and contrast morphological features of the derived waveform. Results: Volitional pharyngeal swallowing and finger movement generated similar waveform characteristics of duration and slope; however, statistically significant differences were identified in polarity and in amplitude at four points both early and late in the epoch. Additionally, swallowing produced a pre-motor waveform with a rapid declination of EEG activity in the final 500 msec prior to movement onset. Conclusions: This study demonstrates activation of the supplementary motor cortex preceding the onset of volitional swallowing. However, unlike purely voluntary movements, the volitional pharyngeal swallowing task, as assessed with this methodology, does not appear to recruit the primary motor cortex. Thus engagement of the swallowing response appears to rely on indirect parallel pathways between extrapyramidal cortical motor planning regions and lower motor neurons.