The most common clinical interventions for orofacial pain and disease include pulpectomy, tooth extraction, and nerve resection that result in the permanent loss of sensory inputs from the dentition. These procedures in turn may result in a number of syndromes affecting the orofacial region, including phantom tooth pain, that appear to arise from plastic changes to the central components of the periodontal neuraxis. However, little is known about the normal organization of periodontal inputs to the cortex or the plasticity of these regions in response to deafferentations.
The aim of the current proposal is to explore the cortical representation of periodontal mechanoreceptors and plasticity of these areas in response to tooth loss. We make use of naked mole-rats for these investigations because they have neural pathways common to other mammals and have an extraordinarily large representation of the dentition that is easily accessible to neurophysiological investigation. In addition, their somatosensory cortex becomes reorganized following tooth-loss. The long-term goals of the proposed research are to determine how the dentition is represented in somatosensory cortex, how these representations change in response to tooth loss, how anatomical modules in the cortex relate to dental inputs, and the location and mechanisms of plastic changes to the cortex. We will use multi and single unit recordings to determine the response properties of cortical neurons representing periodontal mechanoreceptors combined with histological processing of flattened brain sections to identify anatomical subdivisions and areas. Tract tracing techniques and selective inactivation of cortical areas will be used to determine the loci of remodeled afferents that could reactivate the deafferented cortical representations. The long-term goal of these experiments is to identify general principles of brain organization and plasticity.
