title: Pain processing within the primary somatosensory cortex in humans.
abstract: To investigate the processing of noxious stimuli within the primary somatosensory cortex (SI), we recorded magnetoencephalography following noxious epidermal electrical stimulation (ES) and innocuous transcutaneous electrical stimulation (TS) applied to the dorsum of the left hand. TS activated two sources sequentially within SI: one in the posterior bank of the central sulcus and another in the crown of the postcentral gyrus, corresponding to Brodmann's areas 3b and 1, respectively. Activities from area 3b consisted of 20- and 30-ms responses. Activities from area 1 consisted of three components peaking at 26, 36 and 49 ms. ES activated one source within SI whose location and orientation were similar to those of the TS-activated area 1 source. Activities from this source consisted of three components peaking at 88, 98 and 109 ms, later by 60 ms than the corresponding TS responses. ES and TS subsequently activated a similar region in the upper bank of the sylvian fissure, corresponding to the secondary somatosensory cortex (SII). The onset latency of the SII activity following ES (109 ms) was later by 29 ms than that of the first SI response (80 ms). Likewise, the onset latency of SII activity following TS (52 ms) was later by 35 ms than that of area 1 of SI (17 ms). Therefore, our results showed that the processing of noxious and innocuous stimuli is similar with respect to the source locations and activation timings within SI and SII except that there were no detectable activations within area 3b following noxious stimulation.
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan. inui@nips.ac.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Inui
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Wang
authors.forename: Yunhai
authors.initials: Y
authors.lastname: Qiu
authors.forename: Binh Thi
authors.initials: BT
authors.lastname: Nguyen
authors.forename: Shiro
authors.initials: S
authors.lastname: Ojima
authors.forename: Yohei
authors.initials: Y
authors.lastname: Tamura
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nakata
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Wasaka
authors.forename: Tuan Diep
authors.initials: TD
authors.lastname: Tran
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kakigi
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods; D004574:Electromagnetic Fields; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D011930:Reaction Time; D013003:Somatosensory Cortex / Q000502:physiology*; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods