Oscillatory characteristics of nociceptive responses in the SII cortex.
OBJECTIVE
This study is aimed to explore the frequency characteristics of pain-evoked neuromagnetic responses in the secondary somatosensory (SII) cortices.


METHODS
Thulium-laser nociceptive stimuli to the left hand dorsum of 10 right-handed healthy adults. The pain stimuli were rated as mild, moderate, and severe levels according to subjects' reports on a 10-point visual analog scale. We analyzed their cortical responses with wavelet-based frequency analyses and equivalent current dipole (ECD) modeling.


RESULTS
For each pain level, we found an increase of theta (4-8 Hz) and alpha (8-13 Hz) power in bilateral SII areas at 180-210 ms after stimulus onset. The power was larger for the moderate than for the mild pain level (p < 0.05), but there was no statistical power difference of these oscillations between moderate and severe pain stimulus conditions (p = 0.7). Within the SII area, we did not observe particular difference in theta and alpha ECD locations between varying pain level conditions.


CONCLUSIONS
The 4-13 Hz activities, peaking from 180 to 210 ms, are oscillatory correlates of SII activation in response to nociceptive stimulation, but their power may code the magnitude of pain stimuli only up to moderate level, as rated subjectively. This measure could be potentially used to evaluate SII activation in further pain studies.
Hsiao
Fu-Jung
FJ
Institute of Physiology, National Yang-Ming University, Taiwan.
Chen
Wei-Ta
WT
Liao
Kwong-Kum
KK
Wu
Zin-An
ZA
Ho
Low-Tone
LT
Lin
Yung-Yang
YY
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D001683:Biological Clocks / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D007834:Lasers; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D009431:Neural Conduction / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D010812:Physical Stimulation; D011930:Reaction Time / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D013003:Somatosensory Cortex / Q000033:anatomy & histology / Q000502:physiology*