Investigation of brain mechanisms involved in the Urinary Continence mechanism associated with aging
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PROJECT SUMMARY Prevalent, morbid, and costly ($66 billion/year in 2007), incontinence is a major problem, especially for older adults, in whom the most common type is urgency incontinence (UUI). Generally ascribed to bladder spasms, UUI's actual causes are unknown, and therapy remains inadequate. Recent data suggest that one cause is poor bladder control by the brain. In our recent R01 we used biofeedback (BFB) as a probe to explore this. The exciting findings suggest that one `phenotype' of UUI in older adults seems to be caused by a breakdown in brain control, which can be restored by successful behavioral therapy, while another is refractory. Our proposed new study will explore this further by attempting to differentiate the mechanisms associated with disease and aging. The goal is to identify which brain mechanisms should be suppressed because they are contributing to or causing UUI, which should be enhanced because they are helping to compensate for UUI, and which should be ignored because they are incidental to aging and not related to UUI. Current data suggest that bladder control comprises 3 cerebral circuits that maintain continence by suppressing the voiding reflex in the midbrain. In our UUI phenotype that responded to BFB, the mechanism involved enhancing deactivation of the first brain circuit (medial prefrontal cortex, mPFC) which resulted in less activation of the second circuit (which includes the midcingulate cortex). In the phenotype that was resistant to BFB, no brain changes were seen. Yet, although we have an emerging picture of the brain's role in UUI, we have only rudimentary understanding of what is `normal', i.e. how the brain normally controls the bladder. More relevant, we do not know whether this control mechanism is the same across the lifespan, or if it changes owing to the impact of aging. Thus, our overall aim is to characterize continence control in both young and old people, and examine how changes due to bladder control failure differ in each age group. Our specific aims are to characterize normal voiding in the continent old and young in order to better understand and verify the working model and to use the comparison to older adults with UUI to understand the mechanism of brain failure in these individuals. To address these aims, we will conduct a detailed clinical and neuroimaging study to study 80 asymptomatic women and 80 UUI women, each group divided equally into young (18-45) and old (65+ years). The study will enable us to evaluate the changes in brain structure and function and to identify brain mechanisms involved in continence control, changes due to aging (both benign and contributory to UUI), and changes due to disease. The study will provide the comprehensive data on brain mechanisms involved in the normal continence mechanism in order to better corroborate our working model, understand the aging process, and assess targets for therapy. It will thereby enable scientists to develop novel and more effective new therapies based on the revolution in neuroscience—and more hope for UUI sufferers.
