Effect of tactile interference stimulation of the ear in human primary somatosensory cortex: a magnetoencephalographic study.
OBJECTIVE
To confirm the somatotopic representation of the ear in the primary somatosensory cortex (SI), we studied the tactile interference effects on somatosensory evoked magnetic fields (SEFs) following stimulation of the ear (Helix, Lobulus and Tragus).


METHODS
We applied tactile interference stimulation to the neck or face area continuously and concurrently while a time-locked electrical stimulation was applied to the ear. If the amplitude would be reduced by the interference, this would indicate that the cortical representation for both the time-locked electrical stimulation and the continuous interference stimulation overlapped. A two or 3-source model, Source 1 in the neck area of SI, Source 2 in the face area of SI, and Source 3 in the secondary somatosensory cortex (SII), was found to be the most appropriate by brain electric source analysis (BESA).


RESULTS
Amplitudes of Sources 1 and 2 in most interference conditions were decreased. Source 1 following stimulation of all 3 sites was significantly reduced when the interference was applied to the neck area. Source 2 following stimulation of all 3 sites was significantly reduced when the interference was applied to the face area.


CONCLUSIONS
These findings showed that the interference effect was found in both the neck and face areas of SI following the ear stimulation.


CONCLUSIONS
The representation of the ear in SI might be located in both the neck and face areas.
D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D004423:Ear / Q000033:anatomy & histology / Q000294:innervation / Q000502:physiology*; D004558:Electric Stimulation; D004574:Electromagnetic Fields; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005145:Face / Q000294:innervation / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000294:innervation / Q000502:physiology; D010812:Physical Stimulation; D011930:Reaction Time; D013003:Somatosensory Cortex / Q000502:physiology*