Neural correlates of top-down musical temporal processing

For performers and listeners, mentally processing time during musical sequences is essential for executing and understanding the underlying structure and expressive intention in music. In performing classical chamber music for example, the musicians must dynamically monitor their own playing as well as that of their group members for synchrony, they must collectively prepare for and perform rubato or explicit tempo changes, and they must actively track time even when the group has rests instead of notes. Audience members, too, can do such temporal processes as anticipate expressive or scored tempo changes (if they happen to have prior familiarity with the piece), make predictions about the development of a changing musical tempo, and expect certain continuations of the music in time. Notably, the temporal processes mentioned here for both performers and listeners are active, based on voluntary effort put into creating, conveying, or engaging with ongoing music. Moreover, these active temporal processes may be done on top of whatever automatic processes occur due to simply hearing sounds arranged in time. In order to characterize the neural activities that reflect automatic temporal processing, many previous studies have taken bottom-up approaches, driving fixed temporal expectations with fixed stimulus properties and measuring the brain responses elicited by expectation violations after deviating patterns. Only recently have some studies started to investigate the neural activities that result from active temporal processing without manipulating the stimuli. In this dissertation, top-down musical temporal processes were studied in particular by using a unique paradigm with controlled stimuli designed to drive the deliberate processes that musicians and audiences regularly engage in. Specifically, experienced musicians were required to listen to and anticipate tempo accelerations, decelerations, or steady beats after visual cues without knowing when the tempo changes would start. Their electroencephalograms (EEGs) were recorded during this anticipation task, while they continued to monitor the beat sequences for continuity and smoothness during the actual tempo changes, and after each sequence finished. This dissertation presents three studies based on the obtained EEG recordings. Dynamic power modulations of neural oscillations in the beta-band (13-30 Hz) and endogenous evoked response components were analyzed before, during, and after tempo changes. How the targeted neural responses reflected the top-down musical temporal processes of (1) anticipation, (2) temporal interval prediction, and (3) expectation strength are reported in detail. To the field of auditory cognition, this work contributes evidence in support of the hypothesis that the brain actively interacts and engages with stimuli based on top-down goals. Anticipation, direction-specific temporal predictions, and expectations in silence were able to be decoded from ongoing beta modulations and evoked responses, contributing to a neuroscientific understanding of the behavior of beta modulations as well as a musical understanding of what musical temporal processing entails. This work was also the first to document beta modulations during silence after auditory sequences. Finally, compared to standard methods of driving temporal expectation, the paradigm here introduced a more ecologically valid yet EEG-friendly approach to investigate musical temporal processing under experimentally controlled conditions.

Keywords: Music.
Advisor: Fujioka Takako
Chafe Chris 
Slaney Malcolm