September 2016

Measuring The Representational Space Of Music With fMRI
A case study with Sting.
Research paper by Daniel J. Levitin with the Department of Psychology, McGill University, Montreal, Canada and Scott T. Grafton with the Department of Psychological and Brain Sciences, University of California at Santa Barbara

Abstract
Functional brain imaging has revealed much about the neuroanatomical substrates of higher cognition, including music, language, learning, and memory. The technique lends itself to studying of groups of individuals. In contrast, the nature of expert performance is typically studied through the examination of exceptional individuals using behavioral case studies and retrospective biography. Here, we combined fMRI and the study of an individual who is a world-class expert musician and composer in order to better understand the neural underpinnings of his music perception and cognition, in particular, his mental representations for music. We used state of the art multivoxel pattern analysis (MVPA) and representational dissimilarity analysis (RDA) in a fixed set of brain regions to test three exploratory hypotheses with the musician Sting: (1) Composing would recruit neutral structures that are both unique and distinguishable from other creative acts, such as composing prose or visual art; (2) listening and imagining music would recruit similar neural regions, indicating that musical memory shares anatomical substrates with music listening; (3) the MVPA and RDA results would help us to map the representational space for music, revealing which musical pieces and genres are perceived to be similar in the musician's mental models for music. Our hypotheses were confirmed. The act of composing, and even of imagining elements of the composed piece separately, such as melody and rhythm, activated a similar cluster of brain regions, and were distinct from prose and visual art. Listened and imagined music showed high similarity, and in addition, notable similarity/dissimilarity patterns emerged among the various pieces used as stimuli: Muzak and Top 100/Pop songs were far from all other musical styles in Mahalanobis distance (Euclidean representational space), whereas jazz, R&B, tango and rock were comparatively close. Closer inspection revealed principaled explanations for the similarity clusters found, based on key, tempo, motif, and orchestration.

Our understanding of the structure and function of the human brain has been informed over the past two decades by unprecedented advances in neuroimaging technology, particularly by fMRI applied in controlled experiments. Prior to this, nearly all of our understanding of functional neuroanatomy came from case studies, and these remain a prime source of information about the links between brain and behavior. Although case studies lack experimental control – no two lesions are perfectly identical – dozens of case studies have become famous for what they've taught us, such as those of Phineas Gage, Solomon Shereshevsky (Luria's "S"), Louis Victor Leborgne (Wenicke's Tan), and Henry Molaison (Scoville & Milner's HM). Case studies are not deliberate the way that controlled experiments are. They are opportunistic in that they tend to be the result of either workplace accidents, nature's cruelty, or the surgeon's scalpel, chosen by history not because they were the ideal studies but because they came to the attention of a medical doctor or research scientist and provided clues to neural function that could not be obtained in any other way.

One of the biggest unsolved puzzles in contemporary cognitive neuroscience concerns the nature of expertise, and this has rarely been investigated in case studies even though experts are almost by definition unique outliers (notable exceptions are Luria's mnemonist, "S", and the autopsy of Albert Einstein's brain). With the creation of a massive literature characterizing brain function by fMRI, it is becoming increasingly feasible to attempt case studies of remarkable individuals using function as well as anatomic imaging. Clearly, there are some humans who are remarkably better at things than everyone else, and their expertise shows up in a variety of domains such as chess, athletics, science, literature, politics, art, and music. How do experts attain their skill and creativity? To what extent is their achievement based on differences in neuroanatomy or genetic propensities? For expert musicians there are relevant questions concerning the mental representations of music, and how perception, cognition, and memory interact.

The study of music within the cognitive neurosciences offers a compelling avenue for exploring these questions. Music is one of a small set of human universals (Brown, 1991) and there exists wide variation in musical ability within the population. Musical behaviors activate regions throughout the brain, bilaterally, including cortical and subcortical regions, the pons, brain stem, and cerebellum (Levitin & Tirovolas, 2009). Musical expertise requires an exquisite orchestration of brain networks and systems, including those for sensation, perception, decision-making, motor control, memory, attention, problem solving, emotion, and categorization (Levitin, 2007, 2012).

You can read this entire research paper by Daniel J. Levitin and Scott T. Grafton here.