Electrophysiological investigation of temporal interference brain stimulation
File(s)
Author(s)
Zhu, Xiaoqi
Type
Thesis
Abstract
Temporal interference (TI) stimulation is a novel, non-invasive deep brain stimulation technique with promising potential to treat neurological diseases. It non-invasively stimulates the deep brain using the interference of multiple high-frequency electric fields applied via scalp electrodes. Characterising the neural network response to TI stimulation via local field potential (LFP) would help understand and optimise TI stimulation, but it has been limited by TI-generated nonlinear artefacts.
I first unveiled the different sources of the nonlinear artefacts and developed strategies to attenuate them. The artefacts originate from the nonlinearity of the electronics and the electrode electrochemistry. The electronics-originated artefacts are attenuated using well-established electrical strategies, such as hardware filters. The electrochemistry-originated artefacts are attenuated by enhancing the electrochemical performance of the electrodes, such as coating them with high-capacitance conductive polymer PEDOT:PSS. I then demonstrated a proof-of-principle that artefact-free in vivo LFP is concurrently recorded during TI stimulation.
Next, I used the LFP approach to elucidate the fundamentals of the neural response to TI stimulation. TI stimulation strength depends on the stimulation parameters, such as absolute and envelope amplitudes. The applied kilohertz electric fields induce neural response during the ramp-up period (called the onset effect) but not the amplitude-constant period. The undesirable onset effect is attenuated using a longer ramp-up. Finally, I demonstrated a new stimulation strategy that is based on frequency modulation instead of amplitude modulation.
Finally, I developed and tested a strategy to improve the TI stimulation focality at depth by temporally interleaving pulses of TI stimulation. Using computational modelling and single-cell recordings, I showed that the temporally interleaved pulse TI (tip-TI) stimulation has limited feasibility.
I first unveiled the different sources of the nonlinear artefacts and developed strategies to attenuate them. The artefacts originate from the nonlinearity of the electronics and the electrode electrochemistry. The electronics-originated artefacts are attenuated using well-established electrical strategies, such as hardware filters. The electrochemistry-originated artefacts are attenuated by enhancing the electrochemical performance of the electrodes, such as coating them with high-capacitance conductive polymer PEDOT:PSS. I then demonstrated a proof-of-principle that artefact-free in vivo LFP is concurrently recorded during TI stimulation.
Next, I used the LFP approach to elucidate the fundamentals of the neural response to TI stimulation. TI stimulation strength depends on the stimulation parameters, such as absolute and envelope amplitudes. The applied kilohertz electric fields induce neural response during the ramp-up period (called the onset effect) but not the amplitude-constant period. The undesirable onset effect is attenuated using a longer ramp-up. Finally, I demonstrated a new stimulation strategy that is based on frequency modulation instead of amplitude modulation.
Finally, I developed and tested a strategy to improve the TI stimulation focality at depth by temporally interleaving pulses of TI stimulation. Using computational modelling and single-cell recordings, I showed that the temporally interleaved pulse TI (tip-TI) stimulation has limited feasibility.
Version
Open Access
Date Issued
2024-01-15
Date Awarded
2024-07-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Grossman, Nir
Constandinou, Timothy
Grant Number
China Scholarship Council
Imperial College London
Publisher Department
Department of Brain Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)