UC Riverside

Perceptual processes are significantly modulated by the primary neurotransmitter, Norepinephrine (NE). In the brain, the Locus Coeruleus (LC) nucleus located in the pons of the brainstem houses NE production and serves the brain as its sole source of NE. The LC-NE circuit has been shown to play a critical role in modulating various cognitive functions, including sensory processing, perception, and perceptual behavior. However, its complex circuitry, features, size, and location, have challenged our ability to understand the underlying mechanisms of LC’s modulatory role in the human brain. In this dissertation, I investigate the relationship linking LC activity to sensory processing and perception through a series of behavioral, neuroimaging, and physiological studies in healthy young adults. Chapter 1 reviews the literature on LC’s role in modulating cognition, emphasizing the predominant models of LC's relationship with perceptual and memory processes. Chapter 2 reports a behavioral, physiological, and neuroimaging study designed to facilitate understanding LC’s influence on human perceptual, attentional, and decision-making processes. More specifically, behavioral and fMRI paradigms were investigated in conjunction with suitable analytical approaches to address how LC affects the sensory processing of perceptual stimuli in relevant sensory cortex areas. Together, these chapters highlight key findings of LC literature in the context of LC modulation of perceptual processes and behavior, examine influences of LC engagement on behavioral and neural stimulus-response function in humans, and provide an overview of current approaches for evaluating the LC activity related influences on sensory representations and perceptual behavior.