Dissertations, Theses, and Capstone Projects

Date of Degree

9-2026

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Psychology

Advisor

Tony Ro

Committee Members

Elizabeth Chua

Tatiana Aloi Emmanouil

Jin Fan

Jonathan Levitt

Subject Categories

Cognition and Perception | Cognitive Science

Abstract

Visual awareness, the subjective experience of seeing, is not equivalent to the visual information represented by the brain. On the one hand, neural responses to physically comparable stimuli can vary with whether the stimulus is consciously perceived, indicating that visual activity reflects perceptual outcome as well as sensory input. On the other hand, stimulus information can remain represented and influence behavior when awareness of that content is suppressed, indicating that representation alone is insufficient for conscious perception. Early visual cortex (EVC), one of the first cortical areas to receive and represent visual input, is critical for visual awareness and information processing, but its involvement in the dynamic transformation of visual representations into conscious percepts requires further characterization. In the present dissertation, three studies examined how processing involving early visual cortex contributes to the formation of visual awareness and which forms of visual information remain available when awareness is suppressed. In the first study, electrocorticography (ECoG) was recorded during a detection task with backward metacontrast masking. Conscious detection was associated with enhanced population engagement in the occipital visual cortex at intermediate latency beyond the initial registration of the stimuli. In the second study, occipital transcranial magnetic stimulation (TMS) was applied to disrupt EVC activity, combined with concurrent electroencephalography (EEG) when participants reported awareness of the target orientation and then performed a forced-choice orientation discrimination task. Orientation discrimination could remain above chance when TMS over EVC substantially suppressed reported awareness, and discrimination accuracy and awareness showed separate intermediate N2-range and later P3-range prominence in posterior activity, respectively. In the third study, TMS and backward masking were used to test whether global continuity patterns could be discriminated without reported awareness of the configuration. Above-chance performance under awareness suppression showed that residual visual processing can extend beyond isolated features to include relations among spatially distributed elements. Together, the three studies show that EVC contributes causally and dynamically to the formation of visual awareness. Disrupting EVC suppresses reported awareness, but it does not eliminate all visual information available for perceptual judgment. Residual processing can support not only simple feature discrimination, but also judgments based on organizational relations among spatially distributed elements.

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