Adam Tierney

In Vivo Functional and Myeloarchitectonic Mapping of Human Primary Auditory Areas

In contrast to vision, where retinotopic mapping alone can define areal borders, primary auditory areas such as A1 are best delineated by combining in vivo tonotopic mapping with postmortem cyto- or myeloarchitectonics from the same individual. We combined high-resolution (800 μm) quantitative T1 mapping with phase-encoded tonotopic methods to map primary auditory areas (A1 and R) within the “auditory core” of human volunteers. We first quantitatively characterize the highly myelinated auditory core in terms of shape, area, cortical depth profile, and position, with our data showing considerable correspondence to postmortem myeloarchitectonic studies, both in cross-participant averages and in individuals. The core region contains two “mirror-image” tonotopic maps oriented along the same axis as observed in macaque and owl monkey. We suggest that these two maps within the core are the human analogs of primate auditory areas A1 and R. The core occupies a much smaller portion of tonotopically organized cortex on the superior temporal plane and gyrus than is generally supposed. The multimodal approach to defining the auditory core will facilitate investigations of structure–function relationships, comparative neuroanatomical studies, and promises new biomarkers for diagnosis and clinical studies.

Beat synchronization predicts neural speech encoding and reading readiness in preschoolers

Significance Sensitivity to fine timing cues in speech is thought to play a key role in language learning, facilitating the development of phonological processing. In fact, a link between beat synchronization, which requires fine auditory–motor synchrony, and language skills has been found in school-aged children, as well as adults. Here, we show this relationship between beat entrainment and language metrics in preschoolers and use beat synchronization ability to predict the precision of neural encoding of speech syllables in these emergent readers. By establishing links between beat keeping, neural precision, and reading readiness, our results provide an integrated framework that offers insights into the preparative biology of reading. Temporal cues are important for discerning word boundaries and syllable segments in speech; their perception facilitates language acquisition and development. Beat synchronization and neural encoding of speech reflect precision in processing temporal cues and have been linked to reading skills. In poor readers, diminished neural precision may contribute to rhythmic and phonological deficits. Here we establish links between beat synchronization and speech processing in children who have not yet begun to read: preschoolers who can entrain to an external beat have more faithful neural encoding of temporal modulations in speech and score higher on tests of early language skills. In summary, we propose precise neural encoding of temporal modulations as a key mechanism underlying reading acquisition. Because beat synchronization abilities emerge at an early age, these findings may inform strategies for early detection of and intervention for language-based learning disabilities.

The Ability to Move to a Beat Is Linked to the Consistency of Neural Responses to Sound

The ability to synchronize movement to a steady beat is a fundamental skill underlying musical performance and has been studied for decades as a model of sensorimotor synchronization. Nevertheless, little is known about the neural correlates of individual differences in the ability to synchronize to a beat. In particular, links between auditory-motor synchronization ability and characteristics of the brains response to sound have not yet been explored. Given direct connections between the inferior colliculus (IC) and subcortical motor structures, we hypothesized that consistency of the neural response to sound within the IC is linked to the ability to tap consistently to a beat. Here, we show that adolescent humans who demonstrate less variability when tapping to a beat have auditory brainstem responses that are less variable as well. One of the sources of this enhanced consistency in subjects who can steadily tap to a beat may be decreased variability in the timing of the response, as these subjects also show greater between-trial phase-locking in the auditory brainstem response. Thus, musical training with a heavy emphasis on synchronization of movement to musical beats may improve auditory neural synchrony, potentially benefiting children with auditory-based language impairments characterized by excessively variable neural responses.

The ability to tap to a beat relates to cognitive, linguistic, and perceptual skills

Reading-impaired children have difficulty tapping to a beat. Here we tested whether this relationship between reading ability and synchronized tapping holds in typically-developing adolescents. We also hypothesized that tapping relates to two other abilities. First, since auditory-motor synchronization requires monitoring of the relationship between motor output and auditory input, we predicted that subjects better able to tap to the beat would perform better on attention tests. Second, since auditory-motor synchronization requires fine temporal precision within the auditory system for the extraction of a sounds onset time, we predicted that subjects better able to tap to the beat would be less affected by backward masking, a measure of temporal precision within the auditory system. As predicted, tapping performance related to reading, attention, and backward masking. These results motivate future research investigating whether beat synchronization training can improve not only reading ability, but potentially executive function and auditory processing as well.

Music training for the development of reading skills

The beneficial effects of musical training are not limited to enhancement of musical skills, but extend to language skills. Here, we review evidence that musical training can enhance reading ability. First, we discuss five subskills underlying reading acquisition-phonological awareness, speech-in-noise perception, rhythm perception, auditory working memory, and the ability to learn sound patterns-and show that each is linked to music experience. We link these five subskills through a unifying biological framework, positing that they share a reliance on auditory neural synchrony. After laying this theoretical groundwork for why musical training might be expected to enhance reading skills, we review the results of longitudinal studies providing evidence for a role for musical training in enhancing language abilities. Taken as a whole, these findings suggest that musical training can provide an effective developmental educational strategy for all children, including those with language learning impairments.

High school music classes enhance the neural processing of speech

Should music be a priority in public education? One argument for teaching music in school is that private music instruction relates to enhanced language abilities and neural function. However, the directionality of this relationship is unclear and it is unknown whether school-based music training can produce these enhancements. Here we show that 2 years of group music classes in high school enhance the neural encoding of speech. To tease apart the relationships between music and neural function, we tested high school students participating in either music or fitness-based training. These groups were matched at the onset of training on neural timing, reading ability, and IQ. Auditory brainstem responses were collected to a synthesized speech sound presented in background noise. After 2 years of training, the neural responses of the music training group were earlier than at pre-training, while the neural timing of students in the fitness training group was unchanged. These results represent the strongest evidence to date that in-school music education can cause enhanced speech encoding. The neural benefits of musical training are, therefore, not limited to expensive private instruction early in childhood but can be elicited by cost-effective group instruction during adolescence.

Effects of Early Musical Experience on Auditory Sequence Memory

The present study investigated a possible link between musical training and immediate memory span by testing experienced musicians and three groups of musically inexperienced subjects (gymnasts, Psychology 101 students, and video game players) on sequence memory and word familiarity tasks. By including skilled gymnasts who began studying their craft by age six, video game players, and Psychology 101 students as comparison groups, we attempted to control for some of the ways skilled musicians may differ from participants drawn from the general population in terms of gross motor skills and intensive experience in a highly skilled domain from an early age. We found that musicians displayed longer immediate memory spans than the comparison groups on auditory presentation conditions of the sequence reproductive span task. No differences were observed between the four groups on the visual conditions of the sequence memory task. These results provide additional converging support to recent findings showing that early musical experience and activity-dependent learning may selectively affect verbal rehearsal processes and the allocation of attention in sequence memory tasks.

Speech versus Song: Multiple Pitch-Sensitive Areas Revealed by a Naturally Occurring Musical Illusion

It is normally obvious to listeners whether a human vocalization is intended to be heard as speech or song. However, the 2 signals are remarkably similar acoustically. A naturally occurring boundary case between speech and song has been discovered where a spoken phrase sounds as if it were sung when isolated and repeated. In the present study, an extensive search of audiobooks uncovered additional similar examples, which were contrasted with samples from the same corpus that do not sound like song, despite containing clear prosodic pitch contours. Using functional magnetic resonance imaging, we show that hearing these 2 closely matched stimuli is not associated with differences in response of early auditory areas. Rather, we find that a network of 8 regions, including the anterior superior temporal gyrus (STG) just anterior to Heschls gyrus and the right midposterior STG, respond more strongly to speech perceived as song than to mere speech. This network overlaps a number of areas previously associated with pitch extraction and song production, confirming that phrases originally intended to be heard as speech can, under certain circumstances, be heard as song. Our results suggest that song processing compared with speech processing makes increased demands on pitch processing and auditory-motor integration.

Music training alters the course of adolescent auditory development

Significance We show that in-school music training changes the course of adolescent brain development. Relative to an active control group that shows the expected wane in subcortical response consistency, adolescents undertaking in-school music training maintained heightened neural consistency throughout high school. The music training group also exhibited earlier emergence of the adult cortical response, suggesting that in-school music accelerates neurodevelopment. These changes seem to benefit literacy skills: both groups improved in phonological awareness relative to the general population, but the music training group improved more compared with the active controls. Our results support the notion that the adolescent brain remains receptive to training, underscoring the importance of enrichment during teenage years. Fundamental changes in brain structure and function during adolescence are well-characterized, but the extent to which experience modulates adolescent neurodevelopment is not. Musical experience provides an ideal case for examining this question because the influence of music training begun early in life is well-known. We investigated the effects of in-school music training, previously shown to enhance auditory skills, versus another in-school training program that did not focus on development of auditory skills (active control). We tested adolescents on neural responses to sound and language skills before they entered high school (pretraining) and again 3 y later. Here, we show that in-school music training begun in high school prolongs the stability of subcortical sound processing and accelerates maturation of cortical auditory responses. Although phonological processing improved in both the music training and active control groups, the enhancement was greater in adolescents who underwent music training. Thus, music training initiated as late as adolescence can enhance neural processing of sound and confer benefits for language skills. These results establish the potential for experience-driven brain plasticity during adolescence and demonstrate that in-school programs can engender these changes.

The motor origins of human and avian song structure.

Human song exhibits great structural diversity, yet certain aspects of melodic shape (how pitch is patterned over time) are widespread. These include a predominance of arch-shaped and descending melodic contours in musical phrases, a tendency for phrase-final notes to be relatively long, and a bias toward small pitch movements between adjacent notes in a melody [Huron D (2006) Sweet Anticipation: Music and the Psychology of Expectation (MIT Press, Cambridge, MA)]. What is the origin of these features? We hypothesize that they stem from motor constraints on song production (i.e., the energetic efficiency of their underlying motor actions) rather than being innately specified. One prediction of this hypothesis is that any animals subject to similar motor constraints on song will exhibit similar melodic shapes, no matter how distantly related those animals are to humans. Conversely, animals who do not share similar motor constraints on song will not exhibit convergent melodic shapes. Birds provide an ideal case for testing these predictions, because their peripheral mechanisms of song production have both notable similarities and differences from human vocal mechanisms [Riede T, Goller F (2010) Brain Lang 115:69–80]. We use these similarities and differences to make specific predictions about shared and distinct features of human and avian song structure and find that these predictions are confirmed by empirical analysis of diverse human and avian song samples.