This project correlates behavioral responses with neural responses of thalamic projection and non-projection neurons in the medullay dorsal horn (trigeminal nucleus caudalis) produced by noxious thermal stimuli in the behaving monkey. Medullary dorsal horn neurons encode thermal discriminative information used by the monkey to perform a thermal detection task. Many medullary dorsal horn neurons encode thermal intensity in a manner which allows the detection of small changes in noxious temperatures. Certain subpopulations of medullary dorsal horn neurons appear to encode thermal intensity information better at near threshold detection levels than other thermally responsive medullary dorsal horn neurons. Some thermally sensitive neurons also respond to other stimuli used by the monkey for the successful completion of the task. This task-related activity occurs in characteristic patterns of excitation and/or inhibition and some neurons which exhibit such activity project to the thalamus. The neurons examined in this study appear to be important in encoding noxious sensory discriminative information. The task-related responses exhibited by some of these neurons may modulate sensory activity and thereby influence the perception of an response to oral-facial pain.
