Visual stress and reading in special populations; understanding the underpinnings of cortical hyperexcitability

Tempesta, Austyn Joseph ORCID: 0000-0001-5464-503X (2021). Visual stress and reading in special populations; understanding the underpinnings of cortical hyperexcitability. University of Birmingham. Ph.D.

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Abstract

It has been shown that migraines can be triggered by Pattern-Glare stimuli. The epidemic of migraine in the UK, and indeed, the world, is significant. Migraine is the third most common disease in the world. The overarching theme of the PhD thesis is how Pattern-Glare gives rise to behavioural symptoms of Visual Stress and associated electrophysiological correlates in the occipital lobe. This thesis explores this by investigating abnormal (scalp-recorded) EEG responses to clinically relevant pattern-glare gratings (.37, 3, and 12 c/deg, where 3 c/deg is known to be visually aggravating) by undertaking three separate analyses on the same EEG data set. Additionally, we split the data apart between the first presentations of a particular stimulus and its further repetitions, enabling us to explore and distinguish surprise and habituation effects. In Chapter 2, we looked at evoked responses in the time domain, whilst in Chapters 3 and 4, we looked at evoked/induced responses in the frequency domain.
Additionally, Chapter 2 and Chapter 3 investigated questionnaires that were used to assess participants’ headache history (Headache and General Health Questionnaire, HGHQ) and tendency to suffer visual stress (Cortical Hyper-Excitability index (Chi); Visual Discomfort Scale (VDS)). We regressed our EEG data onto these state and trait measures of condition susceptibility, enabling us to identify electrophysiological correlates of these measures. Chapters 2 and 3 found EEG effects that were significant on the headache and discomfort factors, whilst Chapter 4 found significant effects in the theta band. This thesis provides supporting evidence that visual stress (and by extension, migraine, and perhaps epilepsy) is driven by a failure to habituate, with this failure observable in the time-domain (missing N1) and the frequency domain (theta and gamma effects). These findings add to the body of existing knowledge and ultimately may contribute to the further development of clinical interventions in this area.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):