Kozeniauskaite, Karolina; (2025) Functional imaging of pathophysiological neural circuit activity using electrical impedance tomography. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Electrical impedance tomography (EIT) is a novel neuroimaging method which relies on a principle of bioimpedance and its changes with neuronal activity for imaging brain circuits. In recent years, EIT has demonstrated the capability of tracing physiological and pathological neural circuit activity in the rat cerebral cortex with a resolution of milliseconds and micrometres. Thus, EIT represents a unique tool for investigating neural circuit dynamics in rodent models of normal and epileptiform brain activity to improve the diagnostics and therapeutics for pharmacoresistant epilepsy patients. The aim of this thesis was to further develop EIT for a high-resolution real-time imaging of pathophysiological activity throughout the rat brain using intracranial or scalp electrodes. The main purpose of the work was to assess the feasibility of detecting epileptogenic activity anywhere in the rat brain with intracranial depth EIT and assessing its utility in presurgical epilepsy monitoring. Experimental work performed to address the aim and the purpose is presented in Chapters 2 – 6 preceded by a detailed review of the literature and the technical background in Chapter 1. Overall, the results show that, with the present EIT technology, functional imaging of neural circuits in rodent brain cannot be achieved with sufficient resolution using non-penetrating electrodes placed on the scalp (Chapter 2) or on the cerebral cortex (Chapter 3). On the other hand, intracranial EIT with penetrating depth electrodes can track both fast and slow changes during pathological neural activity, such as epileptic seizures, with a mesoscopic resolution of 0.2 – 0.3 mm and ≤20 ms (Chapters 5 and 6). This requires implementation of a novel stereo-electrode array and experimental setup, the development of which is detailed in Chapter 4. Collectively, the finding of this thesis suggest that EIT can produce functional images of brain circuit activity with unmatched spatiotemporal and depth resolution if combined with intracranial depth electrodes. These results support continued development of EIT for research and clinical use with promising prospects in the field of epilepsy.

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