Auditory And Vestibular Efferents PDF Download

"The role of the vestibular efferent system is presently unknown, but evidence based on physiological similarities with the auditory efferent system suggest that it may mediate vestibular end organ development - potentially altering transmission of vestibular information by afferents. To investigate the role of the efferent system, I characterized gaze stabilization and postural control pathways in transgenic mice lacking mediators of efferent signaling ([alpha]-9 and/or [alpha]CGRP). I found that loss of [alpha]-9 attenuated VOR gain, particularly at 4.0HZ, and loss of [alpha]CGRP caused motor deficits during both rotarod and balance beam tasks, consistent with the role of efferents in inner ear development. Finally, to directly assess how loss of cholinergic efferent signaling might influence information transmission I developed methods to record from vestibular afferents of 129SvEv mice during both sinusoidal and random noise stimulation. I found that afferent sensitivity and phase were comparable between both stimulus paradigms, with higher sensitivity and phase lead in afferents with more irregular spontaneous discharge. In contrast, computations of coherence and mutual information revealed that afferents with more regular spontaneous discharge encoded more information content over the natural frequency range of head motion in mice (≤4.0Hz; Beraneck et al., 2008). Taken together, the results suggest this approach will be useful in characterizing changes in sensory information coding in transgenic mice with an impaired efferent system. Overall, my research provides insight into vestibular efferent function and presents future directions for better understanding the underlying physiological changes that occur when this pathways is impaired." --