The effects of noxious heat on responses of spinocervical units to low intensity cutaneous stimuli

The responses of spinocervical neurons to sinusoidal hair displacements were studied during and in the absence of radiant heating of parts of the hindpaw to noxious levels (45-65 degrees C). Noxious heat usually increased background discharge and lowered the signal-to-noise ratio at low frequencies of hair displacement. At higher frequencies over 20 Hz, this ratio was slightly depressed for half of the cells, and dramatically increased for the others. Similar effects were found when the heating was off the receptive field for hair displacement, which suggests a central cause for these effects.