[Response characteristics of the tooth pulp-driven neurons in the 1st somatosensory cortex, especially in the facial sensory area, of the cat].
Unit activities elicited by electrical stimulation of the tooth-pulp and tactile stimulation of the face region were recorded in the face area of the cat's first somatosensory cortex (SI). The tooth pulp driven (TPD) neurons were diffusely distributed in this area and the recording electrode encountered them at the rate of 17.3% (94/542 neurons). All of TPD neurons were also excited by non-noxious tactile stimulation of the face. Therefore, they seem to be polymodal neurons. Although mono-tooth input type neurons appeared at the rate of 15%, the majority of TPD neurons were multi-tooth input type. Many TPD neurons received inputs more dominantly from the mandibular tooth than from the maxillar one, and more dominantly from the molar tooth than from the canine tooth. Half of them received inputs only or dominantly from the contralateral tooth, whereas the incidence of the neurons receiving inputs only or dominantly from the ipsilateral tooth was only about 20%. Generally, many of the former neurons responded with short latencies, while many of the latter neurons responded with long latencies. These findings suggest that the projection pathways from the contralateral tooth to the face area of SI are different from the ipsilateral.