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

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

Waveforms and latencies for N13m and P21m after right side stimulation.

<p>[1] YA subject (25 years old, male), [2] EA subject (71 years old, male). Each waveform shows 10 ms before to 35 ms after stimulus onset. Red and blue arrows indicate peak latencies for N13m and P21m, respectively.</p

Location (XYZ) and orientation (deg) for N13m and P21m in each subject group.

<p>Location (XYZ) and orientation (deg) for N13m and P21m in each subject group.</p

Silver ball electrodes.

<p>(A) Handmade stimulator (silver ball electrode embedded in the handmade clip) and (B) application of the electrode to the left side of the lip.</p

ECD locations and moments of N13m and P21m.

<p>[1] YA subject (25 years old, male), [2] EA subject (71 years old, male). (A) Isofield maps. (B) ECD locations. (C) ECD moment of N13m shows a larger moment in the EA subject than in the YA subject.</p

Mean latencies, ECD moments, stimulus intensity, and interpeak latency in each subject group.

<p>Mean latencies, ECD moments, stimulus intensity, and interpeak latency in each subject group.</p