• F-S Jaw, Y-C Kao, C-P Chen, and W-L Liao.
• Institute of Biomedical Engineering, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan. jaw@ntu.edu.tw
• Neuroscience. 2009 Jan 23;158(2):945-50.

AbstractThe somatotopic map of the first nociceptive component in the primary somatosensory cortex (S1) is still unclear. In this study, a CO(2) laser was applied to the tail of the rat to induce nociception without the interference from large myelinated (A(beta)) fibers. Thus, only noxious fibers could be activated. Two-dimensional current-source-density analysis was used to analyze the evoked field potentials. Using this method, the nociceptive responses of A(delta)-fibers in S1 were verified, and the somatotopic map of the first nociceptive component in S1 was identified. We found that whether light touch or laser-induced nociception was applied to the tail of the rat, the responsive topography in S1 was consistent. Discrimination of these two modalities was achieved vertically in the same column; the deeper layer represented the nociceptive response while the superficial layer encoded the response to light touch. This is quite different from that of a primate brain.

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