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The role of alpha oscillations in visual information processing



The role of alpha oscillations in visual information processing


Stephanie Nelli

Doctor of Philosophy in Neurosciences with a Specialization in Computational Neuroscience

University of California San Diego, 2019

Professor John Serences, Chair

Neural oscillations are one the most prominent features of electrical brain recordings, involving the synchronized activity of large populations of neurons, and have been linked to a variety of important functions over the past century. Existing theories propose these oscillations allow the brain to dynamically switch between functional neural circuits, allowing computational flexibility on time scales too fast for the slow structural changes that characterize long-term cortical plasticity. In particular, alpha oscillations (~8-13 Hz) are often visible in raw scalp electroencephalography (EEG) recordings over visual and parietal cortex and seem to regulate the waxing and waning of visual attention and perception across time. However, many previous results focus specifically on the phase, power or frequency of the alpha oscillation, neglecting the common dynamical systems that simultaneously generate all these metrics and impact visual information processing. In this dissertation, I begin by reviewing relevant literature about alpha oscillations, and then aim to link together disparate measures of the alpha oscillations in both behavior and the brain to address how dynamical alpha state regulates visual information processing. First, in C1 I find that both phase locked and purely power based analyses of imprecise attentional selection display alpha rhythms, suggesting a common impact on behavior. Indeed, in C2 I show that alpha frequency, which governs phase and amplitude are linked mathematically in simple models of harmonic oscillators, which I confirm in neural recordings. Thus, the impact of alpha oscillations on perception depend on circuit interactions with top-down driving oscillators, and in C3 I find that optimal oscillatory drive for visual perception depends intimately on each subject’s particular dynamical system and resultant peak alpha frequency. Together, this thesis challenges core assumptions underlying current theories of the role that alpha oscillations play in regulating visual information processing using both mathematical models and empirical data. I then propose a more unified theoretical framework in which alpha frequency, phase and amplitude should not be viewed as independent metrics to be correlated with behavior, but instead as the result of a common dynamical system that impacts visual perception.

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