Date of Award

Spring 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Neuroscience

First Advisor

Crair, Michael

Abstract

Patterned spontaneous activity plays an instructive role in developing sensory systems. Before hearing onset, inner support cells release ATP and induce spontaneous firing of neighboring inner hair cells. This periphery-initiated spontaneous activity propagates throughout the auditory hierarchy via the afferent pathway, coordinating neural activity in distinct tonotopic zones in the central auditory system. Similarly, spontaneous retinal waves initiated in the retina by starburst amacrine cells (stage II) or bipolar cells (stage III) were observed throughout the visual system via the retinotopic visual afferent circuits. Deciphering the underlying mechanisms of patterned spontaneous activity is critical to elucidate its instructive role in priming the developing nervous system prior to sensory experience. On the other hand, anatomical and functional evidence suggests that centrifugal efferent systems may contribute to neural dynamics before sensory inputs. In the first half of this study, we profiled spatiotemporal and correlational features of auditory spontaneous activity over the entire pre-hearing period. We discovered that the olivocochlear efferent system controlled the coupling strength of bilateral auditory spontaneous activity and demonstrated the profound impact of such modulation on the development of auditory functions. In the second half of this work, we introduced a novel experimental technique that enabled access to in situ retinal calcium dynamics in awake animals. We demonstrated in situ recordings of spontaneous retinal waves from distinct neuronal populations in the retina. Moreover, our result indicated that retinal activity was directly modulated by locomotion. Our approach is well suited to study retinopetal projections in vivo and whether they contributed to locomotion-related modulation on retinal dynamics. Together, these findings provide new perspectives on the functional roles of efferent modulations in shaping spontaneous activity and promoting the development of auditory and visual systems.

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