The Influence of Breathing Pathway on Cognitive Processes

Breathing, a fundamental rhythm of life, has traditionally been associated with the exchange of oxygen and carbon dioxide. However, recent research in both animals and humans has unveiled additional roles of breathing in modulating cortical neuronal activity, influencing sensory, motor, emotional, and cognitive processes, with a particular advantage for nasal breathing in comparison to oral breathing. A small but growing area of research has found a nasal breathing advantage for cognitive processes, particularly attention and memory. The understanding of this advantage is limited.This thesis poses four primary questions:1. Does nasal breathing enhance memory consolidation for stimuli beyond olfaction?2. Is the nasal breathing advantage specific to wakeful rest, or does it extend to a more active cognitive delay period?3. Does nasal breathing influence cognitive processes beyond memory consolidation, such as working memory and attention?4. Can pupil dilation serve as a proxy for respiratory driven neural synchrony that is implicated in the nasal advantage? And is disruption in this synchrony reflected in behavioural performance?Chapter 1 critically discusses the existing literature regarding the influence of breathing pathway on physiology and cognitive processes and identifies the current gaps in the research.Chapter 2 consists of two empirical experiments addressing the first primary question.Experiment 1 examines whether oral breathing disrupts the consolidation of declarative memory.Experiment 2 examines whether oral breathing disrupts the consolidation of perceptual memory.Chapter 3 consists of Experiment 3, which examines the relationship between waking rest and breathing pathway. Previously it has been established that the nasal advantage for consolidation occurs during rest. This study aims to establish if the nasal advantage also persists during an active task, answering the second primary question.Chapter 4 consists of two empirical experiments addressing the third and fourth primary questions. Experiment 4 aims to examine the neural synchrony suggested to occur during nasal breathing using the proxy measure of pupillometry. Pupillometry has been shown to be a reliable indicator of neural activity and breathing has been shown to influence neural activity. Thus, it is suggested that a direct synchronous relationship should exist between the two phenomena. Experiment 5 will establish whether this synchrony between respiration and pupillometry is modulated by breathing pathway, confirming it is a viable proxy measure for the respiratory driven synchrony found during nasal breathing.Chapter 5 contains a stage 1 pre-registered report of Experiment 6, which examines the generalisation of the nasal advantage to visual search and examines how task difficulty may moderate this.Chapter 6 concludes this thesis by summarizing and critically evaluating its contributions to understanding how the breathing pathway affects cognitive processes and physiology. The chapter assesses the two main themes, the influence of the breathing pathway on memory and attention and discusses remaining questions and potential directions for future research.