Encoding of graded noxious skin heating by neurons in posterior thalamus and adjacent areas in the cat

Impulse discharges were recorded from 62 single units in the posterior thalamic and adjacent nuclei of the cat which received input from hindlimb cutaneous nerves. Noxious radiant heating (e.g., 50°C for 10 sec) of the hindpaw excited 32% of the units. The magnitude of heat-evoked unit discharges was graded with the intensity of noxious heating. Such units had large cutaneous receptive fields spanning 2 or more limbs, and responded to strong mechanical stimuli (pressure, pinch). About half of the units responded also to light stimuli such as hair bending or touch.