Somatosensory evoked magnetic fields to air-puff stimulation on the soft palate

Impairment of sensory input to the soft palate has been reported in patients with obstructive sleep apnea syndrome. To investigate the reaction in the central nervous system related to soft palate perception, we measured the somatosensory evoked magnetic fields following air-puff stimulation in seven healthy volunteers by using a helmet-shaped 122-channel neuromagnetometer. The air-puffs were produced using compressed nitrogen and directed to the middle of the soft palate with an intraoral device. To evaluate the laterality of responses we used another appliance in which the air-puffs were directed to the middle and right side of the soft palate. In all the subjects, responses were identified symmetrically in the bilateral parietotemporal regions with a mean latency of about 130 ms from the soft palate stimulation. Prior to this peak, no distinct early responses were observed. There was no significant difference in the responses between the middle and right side stimulation. Corresponding equivalent current dipoles were estimated around the Sylvian fissures. These results suggested that the responses were derived from the second somatosensory areas. In conclusion, we could record long-latency responses to air-puff stimulation of the soft palate in the bilateral second somatosensory areas.