P302 Perception of tactile sensation in the soft palate evaluated by somatosensory evoked magnetic fields

Abstract

Objectives: Although the disturbance of perception in the soft palate caused by the local nerve damage has been reported in patients with obstructive sleep apnea syndrome, no study has dealt with relevant responses in the central nervous system. To investigate the normal physiological mechanism of the perception of the tactile sensation in the soft palate, we measured the somatosensory magnetic fields following air-puff stimulation. Methods and measurements: The somatosensory evoked magnetic fields following air-puff stimulation were measured in 7 healthy volunteers (5 men and 2 women, age ranging from 26 to 41 years, with mean 34.4 years) by using a helmet-shaped 122-channel neuromagnetometer (Neuromag 122, Neuromag, Finland) in a magnetically shielded room. The air-puffs were produced using compressed nitrogen using a Tactile Stimulator (NKP, Yokohama, Japan) and directed to the middle of the soft palate with an intraoral device. In order to mask the noise produced by the air-puffs, binaural white noise (75–80 dB SPL) was used, under which subjects could not hear the onset of air-puff stimulation. To evaluate the laterality of responses another appliance was used. In the appliance the air-puffs were directed to the middle and right side of the soft palate. Results: 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. Conclusions: Long-latency responses to air-puff stimulation of the soft palate could be recorded in the bilateral second somatosensory areas. This method can provide important information on neurophysiological basis of upper airway perception.