Top-down amplification of predicted visual input behind a frosted occluder

Donnelly, Gemma (2022) Top-down amplification of predicted visual input behind a frosted occluder. PhD thesis, University of Glasgow.

Abstract

This thesis is comprised of five chapters. It includes two experimental chapters in which I detail both psychophysical and fMRI studies carried out at the University of Glasgow as part of this PhD project. These are followed by a literature review which outlines the implementation of ultra-high-resolution fMRI, both generally within the field and within a specific project proposal.

Chapter 1 is a general introduction. I outline the broad organisation and basic functions of the visual system at the pre-cortical and cortical stages, in turn. I then discuss the concept of feedback within the visual system, outlining what feedback is, what it does and how it is implemented before outlining the rationale for the thesis.

Chapter 2 is an experimental chapter detailing a series of psychophysical experiments. These experiments employ a partial occlusion paradigm to explore how top-down predicted information can influence the processing of degraded feedforward input. Throughout the experimental series, different aspects of this question are addressed in order to investigate whether the consistency of contextual information influences the detection and/or recognition of low-contrast visual scenes.

Chapter 3 is another experimental chapter which details two 3T fMRI experiments. These projects also employed a partial occlusion paradigm to investigate contextual modulation on the processing of degraded feedforward input at the neuronal level in early visual cortex. Both univariate and multivariate analysis techniques were used to reveal the impact of consistency within top-down information.

Chapter 4 contains a literature review which looks into ultra-high-resolution fMRI. Here, I detail the motivation behind the development of higher resolution imaging as well as potential confounds and limitations. I also outline adaptations required at higher resolution in terms of data acquisition and analysis as well as briefly exploring layer-specific findings within the visual cortex. Finally, I propose a 7T fMRI project that would continue to explore the influence of top-down predictions on the processing of degraded visual input by expanding the investigation to a laminar level.

Chapter 5 is a general discussion which summarises the key points from each of the previous chapters and briefly discusses their conceptual relation to the current field and beyond.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Supervisor's Name: Muckli, Professor Lars
• Date of Award: 2022
• Depositing User: Theses Team
• Unique ID: glathesis:2022-82909
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 31 May 2022 10:35
• Last Modified: 31 May 2022 10:36
• Thesis DOI: 10.5525/gla.thesis.82909
• URI: https://theses.gla.ac.uk/id/eprint/82909

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