The complexity of receptive fields of periodontal mechanoreceptive neuronsin the postcentral area 2 of conscious macaque monkey brains

The representation of the oral structures in area 2 of the postcentral soma tosensory cortex was studied in conscious macaque monkeys by recording sing le-neuron activities. A total of 58 penetrations were made in the oral regi on of five hemispheres in three animals and 707 neurons were isolated. The receptive field characteristics were identified for 480 neurons. Among them , 62 neurons along 21 penetrations responded to mechanical tooth stimulatio n (periodontal mechanoreceptive neurons). The overwhelming majority (81%, 5 0/62) of periodontal mechanoreceptive neurons had receptive fields on sever al teeth in either jaw. Moreover, six had receptive fields on corresponding maxillary and mandibular teeth. Thirty-seven percent (23/62) of periodonta l mechanoreceptive neurons also had receptive fields on other oral structur es surrounding the teeth, such as gingiva (16/23), lip (10/23). and tongue mucosa (1/23). Among them, four neurons had receptive fields on both the gi ngiva and lip. These receptive field features were readily interpreted as a combination of the regions stimulated simultaneously during food intake. W e therefore speculated that these periodontal mechanoreceptive neurons in a rea 2 may be the prerequisite neural substrate for the eventual oral stereo gnosis that will take place in the neighboring association cortices. The co existence of periodontal mechanoreceptive neurons with simple and complex r eceptive fields, or small and large receptive fields in the oral region of the postcentral area 2 suggests that this region could be the stage for the integration of sensory information from the periodontal ligament and from other oral structures. (C) 2001 Elsevier Science Ltd. All rights reserved.