Negative and positive feedback of central nervous system temperature in thermoregulation of pigeons

Experimental alterations of spinal cord and hypothalamic temperature affecting behavioral and autonomic cold defense were investigated in pigeons under external cold load with access to instrumental heat reinforcement. Warming and cooling spinal cord resulted in negative-feedback effects on both instrumental and autonomic cold defense. Hypothalamic warming produced similar negative-feedback effects, whereas hypothalamic cooling produced either no effect or positive-feedback effects on both kinds of cold defense. As determined in previous studies, hypothalamic temperature displacements under heat-load conditions produced only negative-feedback effects on instrumental heat defense. However, only positive-feedback effects were observed on autonomic heat defense by panting. The diverse response patterns of autonomic and behavioral thermoregulatory effectors to changing hypothalamic temperature under heat- and cold-load conditions could be quantitatively described by a mathematical model that takes into account 1) a greater Q10 for intrahypothalamic transmission of the cold signal input than of the warm signal input, and 2) different weights of extra- and intrahypothalamic temperature signal inputs for the control of different effectors.