Assessing the auditory and reward responses to room acoustics and music using functional magnetic resonance imaging

Open Access
Author:
Lawless, Martin Stephen
Graduate Program:
Acoustics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
February 26, 2018
Committee Members:
  • Michelle Celine Vigeant, Dissertation Advisor
  • Michelle Celine Vigeant, Committee Chair
  • Victor Ward Sparrow, Committee Member
  • Daniel Allen Russell, Committee Member
  • Nanyin Zhang, Outside Member
  • Pamela Marie Cole, Outside Member
  • Charles Limb, Special Member
Keywords:
  • room acoustics
  • functional neuroimaging
  • music
  • concert hall
  • reverberation
  • psychoacoustics
Abstract:
Room acoustics considerably change how a listener perceives music because spaces introduce temporal and spatial cues into the auditory signals that can alter subjective impression. In particular, the reverberation of a room can influence a listener’s overall preference to the musical passage. Reverberation has the potential to affect how the auditory and reward networks in the brain respond to auditory signals, but very little work has studied how room acoustics affects these responses even though much research has examined the effect of music. The overall goal of this doctoral work is to investigate the neural response to room acoustics stimuli using functional magnetic resonance imaging (fMRI). Four studies were conducted with express objectives to: 1) substantiate fMRI as an appropriate tool to examine the reward response to room acoustics, 2) establish a concert hall stimulus set to effectively evoke a reward response, 3) investigate the auditory and reward responses to liked and disliked room acoustic conditions, and 4) further explore the auditory response to coherent and incoherent auditory information presented by room acoustics. The first experiment, an fMRI pilot study, was first completed with five subjects to ascertain whether a reward response could be detected in the brain due to variations in room acoustic conditions. The individual- and group-level analyses identified that a reward response to preferred concert hall conditions may be significant with the inclusion of more subjects and a set of concert hall stimuli that more readily elicits listener preferences. The second study, a conventional subjective listening test outside of the MRI scanner with 71 subjects, sought to establish specific musical motifs and room acoustic conditions to improve the stimulus selection process for neuroimaging experiments. Within that objective, the conventional listening study also examined the effect of participant listening expertise on preference to identify suitable candidates for recruitment based on the ability to discriminate between stimuli and the reliability of their preference ratings of reverberant stimuli. A k-means clustering analysis revealed that five groups exhibited starkly different preferences, prompting the selection of individualized stimulus sets for MRI experiments and the recruitment of only expert listeners, defined as musicians. The third and fourth experiments evaluated the auditory and reward responses to the room acoustics stimuli with fMRI. In the third study, auralizations of each individual’s most liked and most disliked room acoustics conditions as well as anechoic musical motifs were presented to 18 participants in an MRI scanner. The results showed that the left and right primary auditory cortices (PAC) activated more so for clearer, simpler stimuli than for the more reverberant, complex stimuli. Specifically, the superior temporal gyri (STG) and Heschl’s Gyri (HG) exhibited higher activations in the presence of the anechoic musical motifs (no room acoustics effects) than the most-liked and most-disliked stimuli. Furthermore, a region-of-interest (ROI) analysis of the caudate nucleus and NAcc revealed significant activations in the contrast of the most-liked and most-disliked stimuli as well as the contrast between the most-liked and anechoic stimuli, which were also disliked by the participants. These activations decisively indicated that room acoustics can evoke a reward response. The fourth study aimed to narrow down the cause of the auditory cortex sensitivity to reverberation, defined as incoherent acoustic information, by presenting all 16 subjects with the same room conditions. The experiment also examined the auditory cortical response to coherent acoustic harmonic content by contrasting the neural responses to the same melody comprised of pure sine tones and trumpet tones, respectively. The results showed that only the presence of reverberation and not the level of the incoherent acoustic information degraded the response of the auditory cortex. Conversely, the presence of coherent harmonic information bolstered the response of the auditory cortex. Since there were no significant interaction effects between the presence of coherent and incoherent acoustic information, these two neural mechanisms were determined to be independent.