The post cingulate's role in triggering voluntary swallowing

Objective To investigate the function of the post cingulate in triggering voluntary swallowing by examining the activated areas in the brain of dysphagic patients with and without delayed pharyngeal swallowing using magnetoencephalography. Methods Videofluoroscopy was used to detect the latency of pharyngeal swallowing of 6 dysphagic patients. Magnetoencephalography (MEG) was used to monitor the whole course of voluntary swallowing, and an equivalent current dipole was applied to the activated areas of the brain 2500 ms before the subconscious electromyographic signals appeared. Magnetic resonance imaging (MRI) was performed just after the magnetoencephalography. A magnetic source image (MSI) was generated by overlaying the MRI and MEG results. Results The MSIs of five of the patients were derived. Three had delayed initiation of pharyngeal swallowing (with the latency being 0.03-0.12 s) and the other two showed normal latency during pharyngeal swallowing. In the former 3 patients, the post cingulate was activated at 1426 ms, 1138 ms and 1675 ms before the burst of electromyography signals, which was later than that of the anterior cingulate and the insular cingulate. The 2 patients without delayed pharyngeal swallowing had their post cingulate activated at 1971 ms and 2483 ms before or at almost the same time as the anterior cingulate and insular. Conclusion Post cingulate activation occurs later than that of the anterior cingulate and insular in patients with delayed pharyngeal swallowing, the reverse of normal swallowing. This result indicates that the post cingulate may play an important role in triggering voluntary swallowing. Key words: Swallowing; Voluntary swallowing; Post cingulate; Stroke; Magnetoencephalography