Functional difference of tooth pulp-driven neurons in oral and facial areas of the somatosensory cortex (SI) of the cat.
Single-unit discharges were recorded in the oral and facial areas of the cat somatosensory cortex (SI) while electrical stimuli were individually delivered to eight tooth pulps. The incidence of the tooth pulp-driven (TPD) neurons was 44.7% in the oral area, but only 17.3% in the facial area. Both sets of neurons were also excited by nonnoxious stimulation of the oral structures or of the facial hair, and thus were polymodal. These TPD neurons were confirmed histologically to be in area 3b and were classified into monotooth input type and multitooth input type according to their response to stimulation. Neurons of the monotooth input type appeared three times more frequently in the oral area than in the facial area. The input(s) to the TPD neurons in the former area were slightly stronger from the canine(s) than from the molar(s), but the opposite was the case in the facial area. In the oral area, 83% of the TPD neurons responded with brisk discharges of short latency, whereas 54% of the TPD neurons in the facial area responded with those of a long latency. These findings suggest that the pulpal information to the somatosensory cortex is conveyed by pathways that appear, at least at certain points in the nervous system, to be spatially separated.
D000200:Action Potentials; D000818:Animals; D002415:Cats; D003782:Dental Pulp / Q000294:innervation*; D005145:Face / Q000502:physiology; D008465:Mechanoreceptors / Q000502:physiology; D009055:Mouth / Q000502:physiology; D009619:Nociceptors / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*