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Abstract
The somatic sensory system responds to stimuli of distinct modalities, including touch, pain, itch, and temperature sensitivity. In the past century, great progress has been made in understanding the coding of these sensory modalities. From this work, two major features have emerged. First, there are specific neuronal circuits or labeled lines transmitting specific sensory information from the skin to the brain. Second, the generation of specific sensations often involves crosstalk among distinct labeled lines. These features suggest that population coding is the mechanism underlying somatic sensation.
Authors
Qiufu Ma
Figure 2
Population coding of thermal perceptions.
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The model is modified from ref. 18 . (A ) Functions and interaction of thermosensitive fibers. Note that CH, CMH, C2, and CMHC fibers all connect with neural pathways involved with hot or burning pain sensation. Activation of Aδ-cold fibers is able to suppress the sense of hot or burning pain. Aδ-cold fiber activity can be masked by the activation of C-warm fibers. (B –F ) Fiber activity (within each rectangle) when a specific sensation (above each rectangle) is evoked. “on” means that the fiber is activated, and “off” means that the fiber is silent or inactivated. CH, C-fibers responding only to noxious heat; CMH, C-fibers responding to noxious mechanical stimuli and heat; C2, C-fibers responding cold and warmth/heat; CMHC, C-fibers responding to noxious mechanical stimuli, heat, and noxious cold; Aδ-cold, A-fibers responding to innocuous cold; C-warm, C-fibers responding to warm temperatures; Aδ-MH, A-type fibers responding to mechanical stimuli and heat.
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ISSN: 0021-9738 (print), 1558-8238 (online)