Cortical Population Dynamics Underlying Choice, Reaction Time, and Confidence

Decision-making is a fundamental aspect of behavior that humans perform ubiquitously and repeatedly throughout their lives. Some decisions are second nature, like deciding to attend class, while others are complex, requiring an abundance of information to consider, such as the decision of which university to attend. However, all decision-making processes share core attributes that encompass the spectrum of complexity. Over the last several decades, scientists have identified and probed these characteristics to unveil the computational and neural underpinnings that make decision-making possible. In addition, these advances have pushed our understanding in other cognitive domains, including perception, attention, memory, learning, reward processing, and others. The essential nature of decision-making has provided an avenue for investigating and comprehending complex cognitive functions at a mechanistic level. The research laid out in this dissertation addresses the neural representation of evidence for a decision, its temporal dynamics and spatial distribution across two levels of the cortical hierarchy, and how it predicts three key behavioral manifestations: choice, reaction time, and confidence. Chapter One presents a general introduction of the perceptual decision-making field both from a behavioral and neurophysiological perspective. Chapter Two describes the novel behavioral paradigm I developed and the main two models I considered throughout this work. Chapter Three summarizes my findings in visual areas MT/MST and neural correlates of choice and confidence. In Chapter Four I detail my electrophysiological results from area LIP, suggesting a parallel strategy for simultaneous reporting of choice and confidence. Lastly, Chapter Five provides a systematic analysis of the training process used to prepare animals for the experiments, elucidating interesting possible theories for learning. All in all, this work demonstrates both the strengths and limitations of current theories within the framework of bounded evidence accumulation, bringing us closer to a comprehensive account of decision formation and confidence judgments.