Je voudrais parler français: Brain activity during sleep supports second language learning Kristen Thompson Thesis submitted to the University of Ottawa in partial Fulfillment of the requirements for the degree of Master of Art in Psychology Department of Psychology Faculty of Social Sciences University of Ottawa © Kristen Thompson, Ottawa, Canada, 2020 ii Abstract Language learning depends on a variety of cognitive abilities, including long-term memory. Sleep is important for the enhancement of memory for newly acquired information and skills. Much of what we know about the relationship between sleep and memory has come from the investigation of two distinct long-term memory systems: declarative (memory for e.g., facts, figures and events) and procedural (memory for e.g., strategy, rules and motor skills). Several sleep-specific electrophysiological markers of memory processing have been identified. More specifically, sleep spindles (bursts of neural oscillatory activity which characterize non-rapid eye movement (NREM) sleep) may be a marker of consolidation for declarative memory (e.g., semantics, facts, figures, events), while rapid eye movements may serve as a marker for cognitive aspects (e.g., grammatical rule-learning) of procedural memory. In adults, second language acquisition (SLA) is thought to depend at first on declarative memory for grammar and linguistic rules (i.e., “early SLA”), and then shifts to procedural memory as the learner gains experience (i.e., “late SLA”). Given the unique roles of spindles and rapid eye movements in declarative and procedural memory consolidation, it was hypothesized that sleep spindles would correlate with language improvement during early SLA, whereas rapid eye movements would correlate with language improvement during late SLA. Eight Anglophone University students (six females, one left-handed, ages: 17-28) completed polysomnographic recordings four times throughout an intensive 6-week French course. Electrode sites W1 and W2 (Wernicke’s area- left and right hemispheres) were used to extract sleep spindle data, as well as examine event-related EEG spectral power time-locked to rapid eye movements. A correlational analysis indicated a significant positive relationship between improvements in French proficiency (post-course minus iii pre-course) and the change in spindle density (early minus late SLA) at electrode W1 for NREM stage 2 and SWS. A nonparametric cluster-based permutation analysis examining event-related power time-locked to REMs, indicated that there was a significant effect of SLA stage (early versus late), whereby an increase in power during late SLA was observed in the theta band. Importantly, this increase in theta power (late minus early) positively correlated with improvements in French proficiency. This follow-up study reveals an important role for sleep spindles in early SLA, and suggests that cortical theta activity during rapid eye movements is a potential marker of learning for cognitive procedural memory during late SLA. Keywords Memory consolidation, second language acquisition, sleep spindles, rapid eye movements, procedural memory, declarative memory, learning, theta. iv Acknowledgments Nothing in life is a solo effort, and this thesis would not have been possible without the support of many people. First and foremost, I would like to express my deepest gratitude to Dr. Stuart Fogel and Laura Ray for your expertise, assistance, and guidance throughout this journey. Thank you for always being there to answer my questions, giving me feedback, and teaching me throughout my degree. Your support is what made this all possible. Furthermore, I wish to express my gratitude to Dr. Joseph De Koninck and Dr. Gilles Hébert. Thank you for providing your guidance and allowing me to be part of such an interesting project. I wish to show my gratitude to the amazing team of students, volunteers, and post-docs in the lab that helped me with this project. A special thank you to Dr. Aaron Gibbings for being part of the research effort and providing your feedback as well as suggesting ideas. Thank you James Shaw for working alongside me, and helping out on this project. Thank you Nicholas Van den Berg for listening to me think through problems, and offering your support. Lastly, none of this would be possible without my dream team of supporters including my family, friends, and partner. My parents Denise and Wayne Thompson, as well as my sisters Nikki and Brittney were always there to give me advice, and support me through everything. Listening to my rants when things went wrong, as well as cheering me on when things went right. You have and always will be my greatest support. Thank you to Antoine Benoit, for providing your support and advice throughout my degree as well as making me feel welcome in Ottawa. To Andreas Grunewald, I wanted to give a special thank you for helping me out as a soundboard and a thesaurus. You always helped me come up with creative ideas to the problems that I encountered. v Table of Contents Abstract ............................................................................................................................. ii Acknowledgments ........................................................................................................... iv List of Tables ................................................................................................................ viii List of Figures .................................................................................................................. ix List of Appendices ............................................................................................................ x List of Abbreviations ....................................................................................................... xi Preface ............................................................................................................................ xii Chapter 1: Introduction ..................................................................................................... 1 1.1 The Study of Sleep. ................................................................................................... 1 1.1.1 Theories of the Function of Sleep. ..................................................................... 1 1.1.2 The Measurement of Sleep. ............................................................................... 2 1.1.3 Sleep Stages. ...................................................................................................... 2 1.1.4 Sleep Regulation. ............................................................................................... 8 1.2 Memory systems. ...................................................................................................... 8 1.2.1 Long-term Memory. ........................................................................................... 9 1.2.2 Memory Types. ................................................................................................ 10 1.2.3 Declarative Memory. ....................................................................................... 11 1.2.4 Procedural Memory. ........................................................................................ 12 1.3 Language. ................................................................................................................ 14 1.3.1 Linguistics. ....................................................................................................... 14 1.3.2 Language Acquisition. ..................................................................................... 15 1.3.3 Second Language Acquisition. ........................................................................ 16 1.4 The Role of Sleep in Memory. ................................................................................ 21 1.4.1 The role of sleep in declarative memory consolidation. .................................. 22 1.4.1.1 Sleep Spindles. ........................................................................................... 23 1.4.1.2 Slow Wave Activity. .................................................................................. 24 1.4.1.3 REM Sleep. ................................................................................................ 24 1.4.2 The role of sleep in motor skill learning. ......................................................... 25 vi 1.4.3 Sleep and cognitive procedural skills. ............................................................. 25 1.4.3.1 REM Sleep and cognitive procedural skills. ............................................... 26 1.4.3.2 NREM2 and cognitive procedural skills ................................................... 28 1.4.4 Sleep & Language Acquisition. ....................................................................... 29 1.4.4.1 Sleep & Semantics. .................................................................................... 30 1.4.4.2 Sleep & Phonetics. ..................................................................................... 30 1.4.4.3 Sleep & the mental lexicon. ........................................................................ 31 1.4.4.4 Sleep & Grammar learning ......................................................................... 32 1.4.4.5 Sleep & Naturalistic Language Learning .................................................. 32 1.4.4.6 Sleep & Hemispheric lateralization during SLA ....................................... 34 Chapter 2: Current Study ...............................................................................................