Thalamic neurons responsive to temperature changes of glabrous hand and foot skin in squirrel monkey

Extracellular discharges were recorded from single neurons located in the ventrobasal thalamus of anesthetized squirrel monkeys. Units with receptive fields on glabrous skin of hand and foot were studied. Only one type of neuron was found that responded to temperature change. These units also responded to mechanical stimuli (T + M units). This finding contrasted with a previous investigation of tongue thalamic thermal projections where units specifically responsive to thermal stimuli were seen in addition to T + M units. This difference was discussed. The neurons were located in the appropriate somatotopic region of VB external intermingled with specific mechanoreceptive neurons. Spinal cord lesions indicated that no sensitive thermal afferents reached the dorsal thalamus via the dorsal columns but probably project via the contralateral spinothalamic system. Response characteristics were analyzed with respect to rapid temperature change. All T + M units responded to cooling with increased discharge rates. No increased rates were seen with warming. It was also determined that the magnitude of the rise in discharge rate to cooling was generally proportional to the degree of cooling.