RUI: Adult Compensatory Plasticity in an Invertebrate Sensory System

Bowdoin College, Brunswick ME

Investigators

Abstract

Non-Technical Paragraph: One of the most important questions in neuroscience is how flexible nervous systems remain as they age. In young organisms, nervous systems are highly plastic; neural cells can change their shape and their function. Older nervous systems tend to be less flexible, and large-scale reorganizations are unusual. This research examines adult plasticity in neural circuits responsible for hearing in crickets, which can regrow and rewire auditory neural connections after damage. This plasticity produces functional recovery of hearing loss that is variable among individual crickets. The goal of this project is to understand the mechanisms that govern this type of plasticity, and to explain the variability in functional recovery among individuals. Because these same or similar mechanisms exist in a wide variety of organisms, what is learned from these cricket experiments will be generally applicable to circuits in other organisms. The broader scientific impact of the work will be its contribution to a deeper understanding of the mechanisms of adult nervous system plasticity and how this knowledge can be used to promote functional recovery after nervous system trauma. This work will also have important educational impacts both at Bowdoin College and within Maine. Undergraduates will be active participants in the proposed scientific research, and a special effort will be made to identify, support, and retain students from underrepresented groups. In addition, the PI and her students will participate in annual STEM outreach activities at local elementary schools and with Wabanaki middle school students, widening the societal impact of the funding. Technical Paragraph: A persistent question about nervous systems is how plastic they remain as they mature. This research project focuses on one of the rare examples of large-scale anatomical plasticity seen in adulthood. The adult auditory system of the cricket Gryllus bimaculatus demonstrates profound structural plasticity after the loss of an ear, consisting of large-scale growth and branching of dendrites and axons. These changes result in wavelength-specific physiological recovery that compensates for the loss of the ear; the extent of recovery in different crickets is highly variable. The PI and her students will test the hypothesis that the extent of anatomical sprouting correlates with recovery, as seen in the strength of physiological responses to auditory stimuli and to behavioral indications of auditory system recovery. The extent of recovery within individual animals will be assessed by testing negative phonotaxis, electrophysiological responses of auditory neurons to sound, and quantifying dendritic and axonal changes in auditory neurons. Bayesian statistical modeling will be used to analyze the data across these levels. Experiments will test whether it is possible to manipulate form and function by altering semaphorin signaling. DsRNA will be used to manipulate sema and plex levels, and any resulting changes in morphology, physiology and behavioral function will be assessed. Given the evolutionary conservation of neuronal strategies for development and plasticity, what is learned from these experiments using G. bimaculatus will be applicable to deafferented circuits in a wide variety of other organisms. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.