title: Cortical responses to C-fiber stimulation by intra-epidermal electrical stimulation: an MEG study.
abstract: Intra-epidermal electric stimulation (IES) is an alternative to laser stimulation for selective activation of cutaneous Aδ-fibers. IES is based on the fact that nociceptive fiber terminals are located in the epidermis, whereas receptors of other fibers end deep in the dermis. IES can selectively stimulate C-fibers if the electrode structure and stimulation parameters are carefully selected. However, stable selective stimulation of C-fibers using IES has proven difficult and cannot currently be used in clinical settings. The purpose of the present study was to determine if IES performed using a modified electrode reliably stimulates C-fibers. Magnetoencephalographic responses to IES to the foot were measured in seven healthy subjects. IES elicited somatosensory evoked fields in all subjects. The mean peak latency was 1,327 ± 116 ms in the opercular region contralateral to the stimulated side, 1,318 ± 90 ms in the opercular region ipsilateral to the stimulated side, and 1350 ± 139 ms in the primary somatosensory cortex. These results indicate that IES performed using the modified electrode can selectively stimulate C-fibers and may be a useful tool for pain research as well as clinical evaluation of peripheral small fiber function.
authors.affiliation: Institute of Advanced Biomedical Engineering & Science, Tokyo Women's Medical University, Shinjuku-ku, Tokyo 162-8666, Japan. Electronic address: motogi.jun@twmu.ac.jp.
authors.forename: Jun
authors.initials: J
authors.lastname: Motogi
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
authors.forename: Minori
authors.initials: M
authors.lastname: Kodaira
authors.affiliation: Institute of Advanced Biomedical Engineering & Science, Tokyo Women's Medical University, Shinjuku-ku, Tokyo 162-8666, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Muragaki
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Inui
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kakigi
mesh_terms: D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D004558:Electric Stimulation; D004817:Epidermis / Q000294:innervation*; D005260:Female; D005528:Foot / Q000294:innervation; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology*; D011930:Reaction Time; D012684:Sensory Thresholds; D013003:Somatosensory Cortex / Q000502:physiology
keywords: C-fiber; Intra-epidermal electrical stimulation; Primary somatosensory cortex; Secondary somatosensory cortex