Evaluating age-related change in lip somatosensation using somatosensory evoked magnetic fields

Abstract

Somatosensory evoked fields (SEFs) to electrical stimulation on the right and left sides of the lower lip were measured using magnetoencephalography and compared in the bilateral hemispheres of 31 healthy normal young and 29 healthy normal elderly subjects to evaluate age-related change in lip somatosensation. The initial peak of the response around 13 ms, designated as N13m, and the second peak of the response, designated as P21m, were investigated. The N13m response, which was detected in 22 of 62 hemispheres in young adults and 37 of 58 hemispheres in elderly adults, showed significantly prolonged latency and increased equivalent current dipole (ECD) moment in the elderly adults. The P21m response, which was detected in 56 of 62 hemispheres in young adults and in 52 of 58 hemispheres in elderly adults, showed longer peak latency in the elderly adults. No significant difference was found in the ECD moment for P21m, which suggests that aging affected the SEFs of the lip somatosensation, but the effects of aging on N13m and P21m differed. Prolonged latency and increased ECD moment of N13m might result from decreased peripheral conduction and increased cortical excitation system associated with aging. Therefore, the initial response component might be an objective parameter for investigating change in lip function with age.

Somatosensory evoked magnetic fields caused by mechanical stimulation of the periodontal ligaments

“…MEG can detect somatosensory responses and locations by recording the weak magnetic fields around human brains caused by neural activity. The oral somatosensory system has been extensively investigated [ 21 , 22 , 23 , 24 ], but few reports have compared the oral senses, especially of the maxillary and mandibular periodontal ligaments.…”

“…Studies using MEG have shown that by observing the latency and intensity of SEFs, it is possible to objectively evaluate the sensory transduction characteristics [ 26 ] of each body part and changes in sensory reception due to age and disease [ 24 , 27 , 28 ]. The present MEG study measured the SEFs to mechanical stimulation of the maxillary and mandibular first molar periodontal ligaments, and investigated the responses and locations of activity in S1 passed through the trigeminal ganglion.…”

Somatosensory evoked magnetic fields of periodontal mechanoreceptors

“…Studies of the SEFs for electrical stimulation of the lip have shown that the first peak of latency called N13m and N15m is difficult to detect [29,30,31]. Additionally, a study showed that early peak latency could not estimate the source location and whether the early peak latency shows the real response was unclear [22].…”

Magnetoencephalographic evaluation of repaired lip sensation in patients with cleft lip

“…The stimulation point of the upper lip center was set at the center of Cupid’s bow ( Fig 1A ). We used a handmade clip with silver-ball electrodes (Unique Medical Co., Ltd., Tokyo, Japan) [ 33 ] to apply electrical stimuli to the lips ( Fig 1B and 1C ). The electrical stimuli consisted of constant current biphasic pulses with 0.2 ms duration delivered at 0.7 Hz.…”

“…Currently, MEG is used widely for detailed measurement of brain functions related to somatic sensations in clinical and research situations. Although MEG has been used to measure SEFs of the oral area to investigate somatotopic organization [ 20 , 24 – 33 ], SEFs of the lips in patients with CL have not been evaluated yet. This study investigated the effects of surgical treatment on lip sensations by comparing SEFs induced by stimulation to repaired lips in patients with CL and normal lips in healthy subjects.…”