Neurotechnology for Multiplexed Interrogation of Brain Circuits and Synaptic Activity

Citation

Hsu, Alice (2023) Neurotechnology for Multiplexed Interrogation of Brain Circuits and Synaptic Activity. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/tba9-sb03. https://resolver.caltech.edu/CaltechTHESIS:06032023-030758184

Abstract

This thesis describes the development of neural technologies for 1) multiplexed brain circuit electrophysiology (ephys) recordings and control of activity in optogenetic mice lines with concurrent recording paired with two-photon imaging and 2) multiplexed measurements of synaptic release events in microfluidic platforms. The first part of this thesis describes efforts to provide deterministic correlation of excited neuron action potential with resulting ephys recordings in vivo. This consisted of technological development of novel, high density multisite silicon probes for electrophysiology recordings in vivo. The probes consist of four columns of electrodes densely packed at the shank tip. This density of electrode arrays allowed for higher resolution isolation of more distinct waveforms than previous ephys probes and benchmarking measurements to triangulate the locations of emitting neurons. These measurements help benchmark the ability of existing silicon extracellular probes to capture surrounding extracellular activity. When combined with two-photon imaging, we can simultaneously record ephys activity, image the probe and surrounding brain, quantify brain damage during probe implantation, and control neural activity using optogenetic mouse lines.

The second project described development of a microfluidic platform to monitor synaptic release of the neurotransmitter glutamate. Microfluidic devices were used to isolate synaptic processes expressing synaptic reporters and provide targeted recording of glutamate activity across the synapse. Synaptic glutamate release was monitored with a two part genetically encoded fluorescent reporter that detects glutamate released at the synapse, called split-iGluSnFR, developed in Professor Lin Tian’s lab at UC Davis. We designed new microfluidic devices to better isolate neuron processes with split-iGluSnFR and be compatible with existing fluorescent complementary metal–oxide–semiconductor (CMOS) contact imagers. Using computational fluid dynamic simulations, we demonstrate efficient perfusion in the device. The form factor of this new device is designed to be compatible with CMOS contact imagers, and that when combined will help us achieve our ultimate goal to monitor the kinetics of simultaneous synaptic release events modulated by perfused neuromodulating drugs.

Thesis Files