Characteristics of the tooth pulp-driven neurons in a functional column of the cat's somatosensory cortex (SI)

The columnar arrangement of tooth pulp-driven (TPD) neurons in the first somatosensory cortex (SI) was studied by single unit analysis in the cat anesthetized with nitrous oxide and halothane. Tactile sensitive neurons in the oral area of SI were arranged functionally in a columnar organization. About 32% of the recorded neurons also responded to tooth pulp stimulation. Thus, the TPD neurons located in area 3b seem to be multireceptive in sensory modality. About 80% of the TPD neurons were F-type which respond with a short latency to tooth pulp stimulation and receive input from a small number of teeth. When a microelectrode penetrated through a single vertical column, most of the F-type TPD neurons encountered received common input from one or two tooth pulps. However, when an electrode was inserted across more than one column, there was no common pulpal input to the TPD neurons encountered in a track. Thus, the TPD neurons in a single column had identical peripheral and pulpal receptive fields, and the same latency of responses to tooth pulp stimulation. These characteristics would support the hypothesis that TPD (presumed nociceptive) neurons are arranged in a vertical column and it may be inferred that the columnar organization of TPD neurons in SI plays an important role in the sensory-discriminative aspects of pulpal pain.