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Date of Award
Doctor of Philosophy (PhD)
The vestibular system generates eye, head, and limb responses to stabilize gaze and posture during motion. While many of the fundamental properties of the central vestibular system have been well-studied, the neural substrates of more complex aspects of vestibular behavior have yet to be established. The intent of the current series of studies was to address two key issues in vestibular sensorimotor processing with a combination of behavioral and neural recording, using the pigeon (Columba livia) as an animal model.
The peripheral vestibular system includes two distinct sets of organs. The semicircular canals are sensitive to angular accelerations experienced during head rotation, and the otolith organs respond to linear accelerations produced by translational movement and by reorientation of the head relative to gravity. Compensatory eye and head responses to movements that stimulate both sets of organs require integration of these distinct sensory signals by the central vestibular system. The nature of this integration was studied using combinations of rotational and translational stimuli, to tease apart the contributions of canal and otolith organ signals to behavior and to neuronal responses in the brainstem. While eye movements were consistent with a linear combination of canal- and otolith-driven response components, head movements were not. This was consistent with recordings in the vestibular nuclei, where neurons known to participate in vestibular head movements exhibited nonlinear integration of canal and otolith inputs.
Additional nonlinear processing by central vestibular neurons was revealed in response to changes in the animal's behavioral state. Gliding flight was simulated in the laboratory using frontal airflow under minimal restraint. The performance of the vestibular head response to rotational stimuli was enhanced during the flight state, improving head-in-space stability. Further, a state-specific tail response was observed that was spatially and temporally appropriate to improve body-in-space stability during flight. The activity of central vestibular neurons was clearly state-dependent, as well. Some neurons only responded to rotational stimuli during flight, while others were sensitive to rotation across behavioral states but had significantly higher firing rates during flight. It is likely that these neurons provide the substrate for state-dependent behavior.
Chair and Committee
Igor Efimov, Jeanne Nerbonne
McArthur, Kimberly Louise, "Neural substrates of vestibular behavior in birds: multisensory integration and state-dependent processing" (2011). Arts & Sciences Electronic Theses and Dissertations. 512.
Available for download on Friday, May 15, 2111