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.
\r\n\r\nThe 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\u2019s 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\u2013oxide\u2013semiconductor (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.
", "doi": "10.7907/tba9-sb03", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:11185", "collection": "thesis", "collection_id": "11185", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09172018-140652131", "primary_object_url": { "basename": "Fowler_thesis_Final_20180924.pdf", "content": "final", "filesize": 66566036, "license": "other", "mime_type": "application/pdf", "url": "/11185/12/Fowler_thesis_Final_20180924.pdf", "version": "v10.0.0" }, "type": "thesis", "title": "Silicon Neural Probes for Stimulation of Neurons and the Excitation and Detection of Proteins in the Brain", "author": [ { "family_name": "Fowler", "given_name": "Trevor Michael", "clpid": "Fowler-Trevor-Michael" } ], "thesis_advisor": [ { "family_name": "Roukes", "given_name": "Michael Lee", "orcid": "0000-0002-2916-6026", "clpid": "Roukes-M-L" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Roukes", "given_name": "Michael Lee", "orcid": "0000-0002-2916-6026", "clpid": "Roukes-M-L" }, { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Lester", "given_name": "Henry A.", "orcid": "0000-0002-5470-5255", "clpid": "Lester-H-A" }, { "family_name": "Moreaux", "given_name": "Laurent C.", "orcid": "0000-0003-1276-5062", "clpid": "Moreaux-Laurent-C" } ], "local_group": [ { "literal": "div_bbe" } ], "abstract": "This thesis describes the development of a number of novel microfabricated neural probes for a variety of specific neuroscience applications. These devices rely on single mode waveguides and grating couplers constructed from silicon nitride thin films, which allows the use of planar lightwave circuits to create advanced device geometries and functions. These probes utilize array waveguide gratings to select an individual emitter from a large array of emitters using the wavelength of incoming light, allowing for spatial multiplexing of optical stimulation. These devices were tested in the laboratory and in living tissue to verify their efficacy. This technology was then modified to create steerable beam forming for stimulation of neurons using optical phase arrays. This technology was also tested for use in fluoresence lifetime imaging microscopy and the first application of pulsed light through the photonic circuits. Finally, this technology was again modified to create laminar illumination patterns for light sheet fluorescence microscopy applications. These devices were further improved by adding embedded microfluidics to the probes. The process of creating embedded microfluidic channels by the dig and seal method is described in detail, including modifications to the procedure that were added to address potential pitfalls in the fabrication process. Next, two projects which combine microfluidics with the optical devices described in the previous chapter are detailed. One project involves combining the use of optical emitters with microfluidic injections containing caged neurotransmitters to stimulate neurons is described. The other project involves microfluidic sampling of the extracellular space for neuropeptides which are detected using ring resonator biosensors. The sensitivity of these biosensors was analyzed in detail, determining both the physical limit of detection and the effect of biological noise due to non-specific binding on the sensors.", "doi": "10.7907/2kvw-ad56", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" } ]