The role of cortical connectivity and functional network analysis of resting-state EEG in Transient Epileptic Amnesia (TEA)

Chandra, Lesley Anne (2024) The role of cortical connectivity and functional network analysis of resting-state EEG in Transient Epileptic Amnesia (TEA). Doctoral thesis (DClinSci), Manchester Metropolitan University.

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Abstract

Transient epileptic amnesia (TEA) is an underdiagnosed sub-type of temporal lobe epilepsy, associated with recurrent amnestic episodes. There is also more persisting memory dysfunction in the form of accelerated long-term forgetting and autobiographical amnesia. EEG investigations form part of the diagnostic work-up but can often be inconclusive. The current research investigated whether resting-state EEG analysis using quantitative EEG and connectivity analysis could provide new insight into the underlying causes of memory dysfunction in TEA. To date, no research literature has utilised connectivity in resting-state EEG to investigate functional and effective connectivity within TEA. Resting-state EEG recordings were acquired from the medical records of 28 patients diagnosed with TEA and compared to age and sex-matched healthy controls. Pre-processing and initial analysis were undertaken using MATLAB, and EEGLAB. Connectivity analysis used three connectivity measures: imaginary coherence, weighted phase lag index and phase transfer entropy. All connectivity analysis was performed using Brainstorm. The results showed functional connectivity alterations across frontal-temporal, frontal-parietal, and temporal- parietal networks within beta, alpha and theta bands. Dysfunction of effective connectivity affecting theta frequencies was seen across all inter-regional networks. Finally, we confirmed that inter-ictal abnormalities were seen more frequently in an independent bi-temporal distribution and were more prevalent during non-REM sleep. Our research has provided new evidence regarding functional and effective connectivity disturbances in people with TEA. We have demonstrated clear and consistent connectivity dysfunction within memory areas of the temporal lobes and memory networks extending within the cortex. The evidence supports the hypothesis that memory consolidation and recall networks are affected in TEA.