title: Nasopharyngeal recordings of somatosensory evoked potentials document the medullary origin of the N18 far-field.
abstract: Because the nasopharyngeal electrode provides non-invasive access to the ventral brain-stem at the medullo-pontine level we used it for recording somatosensory evoked potentials (SEPs) to median nerve stimulation (non-cephalic reference). After the P9 and P11 far-fields, the nasopharyngeal SEPs disclosed a negative-going component which was interpreted as the near-field equivalent of the P14 scalp far-field generated in the caudal part of the medial lemniscus. Nasopharyngeal SEPs also revealed a large N18 with voltage and features strikingly similar to those of the scalp-recorded N18 far-field. These results suggest that N18 is generated in the medulla and not more rostrally in the brain-stem. The use of a nasopharyngeal electrode as reference for topographic brain mapping is discussed. The paper documents the feasibility and relevance of nasopharyngeal recordings for non-invasive analysis of short-latency SEPs.
authors.affiliation: Brain Research Unit, St. Pierre University Hospital, University of Brussels, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Tomberg
authors.forename: J E
authors.initials: JE
authors.lastname: Desmedt
authors.forename: I
authors.initials: I
authors.lastname: Ozaki
authors.forename: P
authors.initials: P
authors.lastname: Noël
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D004558:Electric Stimulation; D004569:Electroencephalography / Q000379:methods*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D009305:Nasopharynx / Q000502:physiology; D011930:Reaction Time