Figure 4.

The coding strategies of temperature sensation. (a) The cooling process but not the absolute low temperature seems to trigger cool sensation, while the absolute high temperature activates spinal cord neurons and leads to heat sensation (123). For noxious cold sensation, it is possible that both the cooling process and the absolute temperature are involved in thermal information processing. (b) At the primary sensory neuron level, cold sensation might adopt a combinatorial coding strategy (N denotes nonresponding neurons, and Y indicates responding neurons). By contrast, heat sensation employs a graded response strategy (117). Meanwhile, some sensory neurons also exhibit graded responses upon cold stimulation (47). (c) In the thermal grill scenario, multiple temperature-sensitive afferent fibers transmit innocuous cool and warm temperature information simultaneously, the cross talk of which can eventually induce a burning hot perception in the brain.