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Joel D Greenspan, PhD

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Neural & Pain Sciences

My laboratory focuses on the neural mechanisms of somesthesis, and physiological factors that influence our perception of touch, temperature, and pain. We have several active areas of investigation, which allows us to gain different perspectives of this complex field.

I. The role of cerebral cortical processing in the various aspects of somesthesis.

A. Brain activation studies (both PET and fMRI) have identified multiple regions in the parietal, frontal and insular regions of cerebral cortex that respond to somesthetic stimulation. We combine psychophysical and fMRI brain imaging techniques to determine what functional roles these various brain regions play in different aspects of somesthetic perception. Both the initial processing regions of cortex (S1 and S2), and the subsequent processing regions (posterior parietal, insular, and cingulate cortices) are of interest, particularly in terms of their relationship to sensory/discriminative vs. affective aspects of somesthesis.

B. Well before there were any in vivo measures of brain activity, the field of functional neurology derived a lot of information about regional brain function from evaluating the performance of individuals with localized cerebral lesions. We have used a combination of high-resolution MRI and psychophysical evaluations to associate specific sensory abnormalities with sites of cerebral pathology. We are now combining such "lesion analysis" with functional brain imaging, in order to better understand the functional changes that occur within the somatosensory system. Of particular interest is the phenomenon of "central pain" – a debilitating and poorly treated pain condition that results from certain brain lesions, principally strokes involving the somatosensory pathways.

II. The bases for gender differences in pain.

It has become increasingly evident that there are gender differences in pain sensitivity, both in laboratory animals and in humans. There are many factors that could account for such differences. We are examining this issue in human subjects by evaluating which neural mechanisms of nociceptive processing show sex differences. We are also examining the question of whether those aspects of nociceptive processing that show sex differences may play a role in pathological pain conditions that are more prevalent in females, particularly temporomandibular joint and muscle disorders (TMJD) pain.

III. Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA).

We are conducting the largest prospective study of TMJD ever conducted, in collaboration with dental schools at the University of North Carolina - Chapel Hill, University of Florida, and University of Buffalo. This NIDCR-sponsored study seeks to identify predictors of TMJD onset and chronicity by evaluating physiological, psychological, and genetic factors that are hypothesized to play a role in chronic pain. Along the way to this end, we are collecting information on pain sensitivity for over 3,400 people, allowing us to learn a great deal about pain sensitivity in the general population, and how such sensitivity relates to psychological and genetic factors.

IV. When Pain Goes Rogue.