Electroencephalography (EEG) is a neurophysiological tool that can be used to study the neural correlates of cognitive processes. Using a tool like EEG over traditional pen and paper tests of cognition can offer greater objectivity of assessments and might also be more sensitive to conditions in which such cognitive processes are impaired (e.g., memory impairment in Alzheimer’s disease; AD). Fast Periodic Visual Stimulation (FPVS) is a method used with EEG to study neural correlates of cognitive processes by virtue of rapid and periodic presentation of stimuli. In an FPVS paradigm a stream of stimuli is presented at a high frequency (e.g., six images per second: 6 Hz) wherein ‘oddball’ stimuli that are categorically different to the standard stimuli are presented periodically (e.g., every sixth image belongs to a different category). The high signal-to-noise ratio and quick administration time (~ 2 minutes for an FPVS task) of this method makes it a promising candidate for use in clinical practice. Therefore, my PhD research has focussed on developing and refining the FPVS method to measure cognitive processes that are impaired early on in conditions such as AD and semantic dementia as well as improving its implementation by testing the reliability of a mobile EEG version of a FPVS memory assessment tool. The main findings of my PhD were: 1) repetition of stimuli in an FPVS paradigm plays a significant role in strengthening the signal measured but is not the sole driver of the oddball response, 2) a mobile EEG version of this tool can reliably detect the FPVS memory signal, 3) implicit semantic discrimination can be measured using FPVS EEG, in the absence of any pre-task encoding, instructions or repetition of stimuli and 4) pre-task encoding of stimuli results in significantly greater FPVS responses compared to repetition priming alone. Overall, the findings of this PhD contribute to the FPVS literature, and the single- vs multiple- systems of memory debate. They also provide supporting evidence for the potential use of FPVS-based assessments to detect impairments in memory in conditions such as AD.
Using EEG frequency tagging to assess memory in healthy younger adults: (Alternative Format Thesis)
Nurdal, V. (Author). 25 May 2022
Student thesis: Doctoral Thesis › PhD