Effects of distraction on magnetoencephalographic responses ascending through C-fibers in humans.
OBJECTIVE
Using magnetoencephalography (MEG), we evaluated the cerebral regions relating to second pain perception ascending through C-fibers and investigated the effect of distraction on each region.


METHODS
Thirteen normal subjects participated in this study. CO2 laser pulses were delivered to the dorsum of the left hand to selectively activate C-fibers. The MEG responses were analyzed using a multi-dipole model.


RESULTS
(1) primary somatosensory cortex (SI), and (2) secondary somatosensory cortex (SII)--insula were the main generators for the primary component, 1M, whose mean peak latency was 744 ms. In addition to (1) and (2), (3) cingulate cortex and (4) medial temporal area (MT) were also activated for the subsequent component, 2M, whose mean peak latency was 947 ms. During a mental calculation task (Distraction), all 6 sources were significantly reduced in amplitude, but the SII-insula (P < 0.01) and cingulate cortex (P < 0.001) were more sensitive than the SI (P < 0.05) and MT (P < 0.05).


CONCLUSIONS
We confirmed that SI in the contralateral hemisphere and SII-insula, cingulate cortex and MT in bilateral hemispheres play a major role in second pain perception, and all sites were much affected by a change of attention, indicating that these regions are related to the cognitive aspect of second pain perception.


CONCLUSIONS
The SI, SII, cingulate and MT were activated during the C-fiber-related MEG response, and responses in these regions were significantly diminished during mental distraction.
Qiu
Yunhai
Y
Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan. yhqiu@nips.ac.jp
Inui
Koji
K
Wang
Xiaohong
X
Nguyen
Binh Thi
BT
Tran
Tuan Diep
TD
Kakigi
Ryusuke
R
D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology; D001288:Attention; D002540:Cerebral Cortex / Q000503:physiopathology; D004569:Electroencephalography; D006179:Gyrus Cinguli / Q000503:physiopathology; D006801:Humans; D007834:Lasers; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D036421:Nerve Fibers, Unmyelinated; D010146:Pain / Q000175:diagnosis / Q000503:physiopathology* / Q000523:psychology*; D010775:Photic Stimulation; D011930:Reaction Time; D012016:Reference Values; D013003:Somatosensory Cortex / Q000503:physiopathology; D013702:Temporal Lobe / Q000503:physiopathology