Lara-Garvija
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On Musical Rewards: ‘Defrosting’ musical chills with Naltrexone Lara Garvija Submitted as Master Thesis in Cognitive Neuroscience At Department of Psychology UNIVERSITY OF OSLO Autumn Semester, October 2019 On Musical Rewards: ‘Defrosting’ musical chills with Naltrexone By Lara Garvija Master of Cognitive Neuroscience Department of Psychology UNIVERSITY OF OSLO October 2019 Ó Lara Garvija 2019 On Musical Rewards: ‘Defrosting’ musical chills with Naltrexone Author: Lara Garvija Supervisors: Bruno Laeng & Siri Leknes http://www.duo.uio.no Print: Reprosentralen, Universitetet i Oslo Acknowledgments As an amateur musician of 14 years with aspirations in the field of neuroscience, it was deeply gratifying to combine both interests in the present study. From raiding my father’s cabinet of 80’s albums, to the pleasures of performing sonatas, I was exposed to the immense rewards of listening to and making music at a young age. For many years I had longed to merge my love for science and music, taking cross-institutional classes in music cognition throughout my bachelor’s degree. Thus, the opportunity to do so in this thesis has been an exciting work of passion. I want to thank Bruno Laeng (Department of Psychology and ‘RITMO Centre for Interdisciplinary Studies of Rhythm, Time and Motion’) and Siri Leknes (Department of Psychology and ‘The Leknes Affective Brain lab’) for exceptional supervision from the conception of the research question, design, and, thereafter, assistance in interpretation of the results. This project would not have been possible without the immeasurable support and assistance from both of my supervisors. I would also like to thank my colleagues Aftab Bakhtiari and Maria Gunnarsen (credited in the text with their initials - AB and MG) for helping with part of the data collection, and to the participants willing to partake in the project. I would like to thank Dan Mikael Ellingsen, Remy Meir, and Erik R. Frogner of the study running in concert with the current project, for assistance in recruiting participants as well as sharing valuable ideas on the study. In addition, I would like to express my gratitude to Guro Løseth, Marie Eikemo, and Gernot Ernst of the Leknes Affective Brain lab for providing tutelage on participant screening and helping with decisions concerning the use of naltrexone. Lastly, special thanks go to my friends and family for extensive moral support and encouragement throughout this experience. IV Abstract Author: Lara Garvija. Title: On Musical Rewards: ‘Defrosting’ musical chills with Naltrexone. Supervisors: Bruno Laeng and Siri Leknes Studies exploring the neurochemical underpinnings of basic, evolutionary rewards (i.e. tasty food and sex) have consistently implicated the endogenous opioid system during peak moments of consummatory pleasure. Less is known about the role of opioids while listening to pleasant music, despite being rated one of the top 10 most rewarding human experiences. In fact, music is known to be so deeply and powerfully pleasant that it can elicit intense, emotionally-charged physiological sensations, or ‘chills’. We hypothesised that an opioid antagonist would decrease hedonic valence and/or arousal to self-selected, favourite musical pieces. Fifty male and female individuals participated in a music-listening task with a counterbalanced, placebo-controlled double-blind design. Participants were orally administered an opioid antagonist (50mg naltrexone) or placebo (40µg d3-vitamin) over two sessions, a week apart. One hour after pharmacological intervention, participants listened to music while eye-tracking data was collected. The songs presented were self-selected pieces, highly pleasant and even chill-inducing for each individual participant. In addition, each individual listened to another set of (control) songs that were similarly provided by an age- and sex-matched individual. While listening to each musical selection, a participant looked at an on-screen visual analog scale termed the ‘chillometer’, directing gaze vertically along the ‘thermometer’ scale according to the felt moment-to-moment hedonic response. In the present study, music chills were found to last approximately four seconds with great inter- individual differences, a novel addition to the scientific literature on the duration of peak musical rewards. Results revealed that while hedonic valence was not systematically altered by naltrexone, there was a general diminished level of arousal to both song types, indexed by a smaller pupillary diameter and more so for ‘chilling’ moments, beyond the expected generic reductive effect naltrexone has on the pupil. Crucially, with naltrexone, pupil size during self-selected songs was smallest while experiencing music chills than for the other hedonic levels. These findings, taken together, suggest that the opioid system may modulate arousal more than hedonic valence, at least in relation to musical peak experiences as chills. Overall, our findings are only partially consistent with our initial hypothesis. V Table of Contents 1 Introduction .................................................................................................................. 1 2 Theoretical framework ................................................................................................. 2 2.1 A brain’s ‘common currency’ for rewards ....................................................................................... 2 2.2 A neurochemical perspective on musical reward ............................................................................. 3 2.3 Music chills ........................................................................................................................................ 5 2.3.1 Physiological sensations ........................................................................................................... 7 2.3.2 Acoustic features ..................................................................................................................... 7 2.3.3 Individual and contextual factors .............................................................................................. 8 2.3.4 General frequency of music chills experiences .......................................................................... 8 2.3.5 The biological origins of chills ................................................................................................. 9 2.4 Pupillometry and oculomotor behavior of music listening ............................................................. 10 3 The present study ........................................................................................................ 12 3.1 Hypotheses and predictions............................................................................................................. 13 3.2 Methods ........................................................................................................................................... 15 3.2.1 Participants ............................................................................................................................ 15 3.2.2 Stimuli ................................................................................................................................... 16 Musical stimuli ...................................................................................................................... 16 The ‘chillometer’ scale of ‘hedonic temperature’ .................................................................... 18 Pharmacological intervention ................................................................................................. 19 3.2.3 Set up and procedure .............................................................................................................. 20 3.2.4 Data processing ..................................................................................................................... 22 4 Results ......................................................................................................................... 24 4.1 Subjective ratings and eye fixations ................................................................................................ 24 4.2 Pupillary diameters ......................................................................................................................... 26 4.2.1 Silent period and white noise after tablet administration.......................................................... 26 4.2.2 Silent periods prior to listening trials ...................................................................................... 26 4.2.3 Pupil diameter grand means during listening trials .................................................................. 27 4.2.4 Pupillary diameters with positive ratings and Chills ................................................................ 28 4.2.5 Mean fixation durations within the chillometer ....................................................................... 30 4.2.6 Mean duration of a music chill ............................................................................................... 31 4.3 Blink Frequency .............................................................................................................................. 32 4.4 Music chills questionnaire responses .............................................................................................. 33 4.5 Drug detection ................................................................................................................................