Neurophysiological and acute pharmacological studies in FXS patients

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Sensory hypersensitivities are common and distressing feature of the Fragile X Syndrome. This clinical symptom is believed to be associated with neuronal hyperexcitability in neocortex. There are three primary goals of our highly novel and integrated Center program as pursued in Project 3. First, we aim to characterize the neural substrate of auditory sensory hypersensitivities in Fragile X patients using clinical neurophysiology. Second, we will establish mouse-human homologies via parallel 'in vivo' auditory neurophysiology studies in P2 and P3. Third, we will examine neurophysiological effects of single dose administration of minocycline, acamprosate, and lovastatin on resting EEG and auditory evoked responses in patients with FXS, using the same paradigms as in the Fmr1 mouse studies of P2. Auditory sensory responses, repeatedly shown to be highly abnormal in the Fmr1 mouse model and FXS patients, will be analyzed from a bottom-up, local circuit perspective by examining early sensory evoked response amplitudes and habituation to repeated tones. We will also analyze top-down corticocortical control of auditory processing using our recently established talk/listen paradigm. Last, we will perform a time-frequency decomposition of the EEG response to amplitude modulated (AM) chirp stimuli in order to examine local circuit-mediated neural oscillations. For the chirp paradigm, we will focus particularly on higher frequency gamma band activity, which we have found to be highly abnormal in Preliminary Studies in Fragile X as predicted by the neural circuitry model being tested in P1. Data will be examined for correlations between CGG repeat number and gene methylation, and with clinical ratings. Together with the mouse auditory circuit studies in PI & P2, pharmacological studies in P1 & P2, and 'in vivo' mouse auditory processing studies (P2), we will develop a mechanistic understanding of auditory hypersensitivity in Fragile X patients, and more broadly about illness mechanisms and translational strategies for evaluating neuronal hyperexcitability and its clinical impact.