Cortical Representational Plasticity of Oral Structures

Vanderbilt University, Nashville TN

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Abstract

DESCRIPTION (provided by applicant): Great progress has recently been made in our understanding of cortical areas related to touch, particularly regarding the plasticity of adult neocortex. This has provided important insights into phantom limb sensations, recovery from stroke, and the basic neurophysiological correlates of sensorimotor learning. Yet our understanding of the cortical representation of the dentition has lagged far behind. Plasticity of dental representations is of particular importance to human health, given the ubiquity of tooth loss and the common need for dental implants and prosthetics. To begin to address these issues, the current proposal makes use of a favorable new model system, the naked mole-rat, to investigate the cortical representation of dentition. Naked mole-rats have an extraordinarily large representation of the dentition that is easily accessible to neurophysiological investigation. 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 or disuse at different developmental stages, and how anatomical specializations (modules) in the cortex relate to dental inputs. We will use multi and single unit recordings to determine the response properties of cortical neurons representing functional classes of periodontal mechanoreceptors and possible modular segregation of slowly adapting (SA), rapidly adapting (RA) and directionally selective receptors in both primary (SI) and secondary (S2) somatosensory cortex. Neurophysiological recordings will be combined with histological processing of flattened brain sections to identify corresponding architectonic subdivisions. After determining the normal cortical organization, plastic changes in cortex will be assessed in adults and juveniles with the same methods after extracting individual teeth, or after behavioral disuse due to tooth trimming. We hypothesize that the cortical representation of periodontal inputs will have a modular organization and will exhibit considerable adult plasticity, but may be limited in degree by early sensitive periods of development.