The responses of relay cells in the human thalamic ventral caudal nucleus (Vc) was explored in a set of experiments designed to study neuronal firing patterns evoked in humans by pain and thermal cutaneous stimuli. Cells responsive to cold or painful stimuli have been found to produce low threshold spike (LTS) bursting preferentially in response to these stimuli. This appears to be an intrinsic thalamic phenomenon and not a firing pattern produced by input from the periphery. Microstimulation within the Vc during awake surgical procedures demonstrates that cold and pain sensations can be evoked by short bursts of electrical stimuli in a pattern similar to that observed during neuronal LTS bursts. These results strongly suggest that that cold and pain sensations may be mediated in part by human thalamic LTS burst firing patterns.
