12 Oct Shaping our understanding of endothermic thermoregulation
The paper by Kobayashi entitled “Temperature receptors in cutaneous nerve endings are thermostat molecules that induce thermoregulatory behaviors against thermal load”1 summarizes a series of elegant studies conducted by Kobayashi and colleagues during the past 30 years. These studies have challenged the “hypothalamic proportional control” model which remains the most widely accepted approach for the functional architecture of endothermic thermoregulation over the past 50+ years.2 Kobayashi opposes the dogma that receptors are sensors, arguing instead that receptors are “comparators.”1 He proposes that heat- and cold-sensitive neurons are comparators of temperature and evoke impulses when temperature surpasses a receptor activation threshold. In turn, these impulses are not a form of neural code (as assumed by the “hypothalamic proportional control” model) but they are actually triggers to activate target effector neurons in the brain. For instance, when skin temperature is below its threshold value, peripheral cold-sensitive neurons evoke impulses to stimulate target neurons in the brain responsible for appropriate heat-seeking responses. Consequently, skin coolness “…only occurs in the sensation world in our mind.”3 Ergo, the “comparator” model suggests that effectors are triggered via sensory neurons directly, without the involvement/presence of a separate decision-making network or temperature code computations.
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