Designing, building and testing a UV photouncaging system to study the development of the auditory brainstem

Abstract

New abstract (saved as much of your structure/wording as possible): In mammals, sound localization along the azimuth is computed in part in the lateral superior olive (LSO), a binaural nucleus in the brainstem. Information about the location of the sound source is derived from differences in sound intensity at the two ears, the Interaural Level Difference (ILD). Within each LSO, principal cells compute ILDs by integrating an excitatory input carrying intensity information from the ipsilateral ear with an inhibitory input carrying intensity information from the contralateral ear. This computation requires that the phenotypically distinct inputs onto individual LSO cells be matched for sound frequency. The process of ‘aligning’ and refining the inputs for frequency information occurs during the first few postnatal weeks in rats, through modifications of synapse strength and cell morphology. Our lab studies the distribution, and re-distribution, of these converging inputs during the early period of circuit refinement.

A common strategy for examining spatial distribution of synapses is through anatomical techniques, including for example immunohistological methods for localizing specific synaptic proteins. Ultimately, however, we need to understand how synapse position affects the functional response. Asking this kind of question requires the ability to stimulate individual synapses while recording from dendrite or cell body, an approach for which we use laser scanning photostimulation (LSPS). I designed two LSPS systems in order to stimulate the post-synaptic sites of excitatory or inhibitory inputs on LSO principal neurons while recording at the cell body using whole-cell patch clamp. I researched many optical designs and technologies when fine-tuning my design. My designs and initial groundwork will help a future lab member finish one or both of the LSPS designs.