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Title: Imaging of evoked neural activity in the rat brain using Electrical Impedance Tomography
Author: Faulkner, Alice Constance Mayo
ISNI:       0000 0004 8500 2258
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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Electrical impedance tomography (EIT) is a technique that can reconstruct conductivity changes in a volume from multiple transfer impedance measurements. Impedance changes associated with neuronal depolarisation can be measured and hence the use of EIT as a functional brain imaging technique has been proposed. The work presented has sought to extend EIT in the rat model from an exclusively cortical imaging technique to one sensitive to subcortical activity. Chapter 1 provides an introduction to the principles of EIT and an overview of previous EIT experiments. Chapters 2 and 3 have focused on optimising parameters for imaging subcortical activity when using cortical electrode arrays. In chapter 2, EIT protocol generation methods aimed at enhancing sensitivity to deep regions of interest in the brain were developed. The protocol that maximised the magnitude of current density was found to be optimal. The best frequency at which to conduct EIT measurements was determined in chapter 3 by characterising the impedance response in the thalamus and cortex during somatosensory stimulation using carrier frequencies up to 10 kHz. The largest SNR in both the cortex and thalamus was observed at 1475 Hz. The ability to image ascending neural activity with cortical electrodes was investigated in chapter 4. Despite using the optimised parameters found previously, the small amplitude signals from the thalamus precluded imaging deeper than the cortex. Subsequent simulations indicated that with this type of electrode, EIT imaging is limited to 2.6 mm below the cortical surface. In chapter 5, the feasibility of conducting EIT measurements with neural probes was assessed. By implementing neural probes along with cortical electrode arrays, thalamo-cortical circuitry occurring at the correct latency during somatosensory stimulation was imaged. The configuration of neural probe implemented limited the localisation accuracy of thalamic activity to 1.3 - 1.7 mm.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available