Neurobiology of Beat Synchronization: Impact on Pre-School Language Development

Lay Summary

Neurobiology of Beat Synchronization: Impact on Pre-School Language Development

Investigators will explore whether preschool childrens’ pre-reading skills track with their rhythmic abilities, and whether common brain processes underlie both skills.

About one in every 15 children has a reading disorder that can confer lifelong consequences for learning. The most common of these is dyslexia, where the reader has difficulties differentiating sounds, recognizing written words and spelling. Areas of the brain including the medial geniculate body in the auditory thalamus have been implicated in dyslexia, but the biology of reading disorders in general remains unknown.

An intriguing link has been found between an individual’s ability to read and to synchronize to rhythms. Evidence suggests that rhythmic sensitivity cues the listener to several components of understanding language. These cues include stress of the appropriate syllable in a word, identification of changes in tone that differentiate questions from statements, and discrimination of sounds such as “boy” versus “toy.” Developmentally, speech rhythm is one of the earliest cues that infants use to segment and discern speech through its sounds. People with dyslexia and other reading disorders, however, struggle to pick up on these rhythmic patterns. This inability may reflect a deficit in the timing with which the brain processes speech sounds. Deficient speech-sound processing also may create difficulties determining which acoustic distinctions in speech are meaningful, an important pre-reading skill.

Taken together, according to Northwestern University investigators, sensitivity to changes in speech sounds influences the brain’s processing of discrete components of speech. A breakdown in this process, therefore, may impede awareness that words are made up of a variety of sounds, and that language entails a systematic organization of these sounds.

Research has shown an intriguing link in school-aged children between how well they read and their rhythmic competency, measured in terms of how accurately they tap along to a metronome. Conversely, those who struggle to synchronize to a beat similarly struggle with reading and have deficient neural processing (encoding) of sound. The Northwestern investigators found a surprising degree of heterogeneity in the precision by which people perceive and produce a steady beat (“beat-keeping”) roughly at the syllable rate of speech. Such differences track systematically with reading abilities and with associated cognitive, perceptual and neurophysiological functions.

These investigators have preliminary evidence of a similar link between reading and rhythm synchronization in preschool aged children. They found that preschoolers (aged three or four) who score well at tapping to a beat also score well on tests of reading readiness and have strong neural processing of speech rhythms. By characterizing these beat-keeping skills and examining the reading-rhythm link in preschoolers, the investigators aim to gain insights into the preparative biology of reading and to pinpoint the role of rhythmic synchronization in language development.

Their central hypothesis is that neural timing and synchrony in the auditory system provide overlapping support to rhythmic synchronization and language performance. They anticipate that rhythmic skills complement other skills, such as sensitivity to speech sounds in consonants, which guides reading development. Given the paucity of research, however, they note that they can only begin to speculate on which aspects of rhythmic synchronization and reading overlap.

They will pursue two aims: 1) Determine how early language skills are linked to a preschooler’s synchronization ability, anticipating that those with superior rhythmic synchronization abilities have strong speech sound processing and associated reading readiness skills; and 2) Identify the shared biological mechanisms underlying synchronization ability and pre-reading skills, anticipating that the temporal precision required for both rhythm and reading is provided by precise timing in the auditory system across multiple time scales. Further, the encoding precision will be more pronounced in how the brain encodes the varied speech rhythms that are theorized to be foundational to language development (“envelope” features) as opposed to how the brain encodes finer speech sounds.

Investigators will enroll 80 preschool-aged children and study them at baseline and one year later to answer three questions: 1) how are beat-keeping, pre-reading skills and neurophysiology interrelated during childhood? 2) How do these functions develop? And, 3) how is the development of these functions interrelated and do children with proclivities for one function (beat-keeping) show more rapid development of pre-reading skills?

The experimenter and each child will perform a bongo drumming task. They will drum at two sequential rates. For each of the two rates, every child will be assessed in terms of how reliably they synchronize to the beat, and how consistently each child drummed on the beat. Investigators will assess pre-reading skills based on each child’s performance on measures that are predictive of these skills.

To identify the biological processes that reading and rhythm synchronization share, investigators will measure each child’s auditory processing of speech cues under conditions of quiet and noise using an electrophysiological technique that they developed. The technique, which measures how precisely the brain processes sound, is called “cABR” (auditory brainstem response to complex sounds). As investigators present speech sounds (syllables and words), cABR measures the brain’s neuroelectric responses through sensors affixed to the scalp.

The response reflects what the brain hears. Amazingly, the brain’s response sounds much like the stimulus. This stimulus-response symmetry enables the investigators to determine how the rhythms of speech, the boundaries (starts and stops of the sound), intonations, and consonants are processed by brain. Results track systematically with the child’s speech and language skills and can be used repeatedly, therefore, to monitor each child’s biological development of reading skills.

This technique provides a biological snapshot of the listening brain. Although the cABR is generated predominately in brainstem cells, it reflects cortical influences from attention, working memory and life experience. It reflects the entire auditory processing circuit of interest and, therefore, cABRs have a profound neurodiagnostic potential. Taken together, the results obtained initially and at one year later are anticipated to identify which pre-reading skills do and do not track with rhythmic ability and what underlying neural processes are common to both types of skills.

Significance: The results are anticipated to facilitate the design of targeted rhythm-based interventions for young children who exhibit delays in reading and language development. Results should also inform the development of objective biological markers of language skills in pre-school children.

Abstract

Neurobiology of Beat Synchronization: Impact on Pre-School Language Development

SPECIFIC AIMS Reading disorders affect 5-10% of children and carry devastating lifelong consequences for learning, educational attainment, and economic standing. Considerable resources have therefore been dedicated to understanding the biological and cognitive architectures that support reading development. As a part of this effort, an intriguing link between an individual’s reading and rhythmic synchronization abilities has been discovered. It is thought that rhythmic sensitivity cues a listener into syllabic stress and prosodic patterns in speech; these representations come to bear when a child begins reading, and impoverished processing of syllabic level information impedes reading development. To date, however, evidence of the rhythm-reading link has been observed in children of school age or older—that is, individuals who have developed their reading skills. Therefore, the idea that rhythmic sensitivity supports reading development remains conjecture. We aim to fill this research gap by exploring the link the rhythm-reading link—and its neural foundations—in children who are just starting to read. By understanding the rhythm-reading link in pre-readers, we can pinpoint the role rhythmic synchronization plays in language development. We have developed a suite of rhythmic and biological measures for use in adults that we will adapt to pre-schoolers. These measures break down rhythmic ability into subcomponents (synchronization to a metronome, remembering rhythmic patterns, perceiving the beat of complex stimuli) that can be mapped to facets of auditory processing (for example, neural tracking amplitude modulations v. frequency modulations) and pre-reading skills (phonology, memory, rapid naming, etc.). A deep and fine-grained understanding of which pre-reading skills track with rhythmic ability, and their common underlying neural mechanisms, will allow for the design of targeted assessment and interventions on an individual level for young children exhibiting delays in reading and/or language development. We aim to combine our analysis of the rhythm-reading link in toddlers with biological measures of auditory processing at subcortical and cortical levels. By considering the neural processing of speech cues, neural sensitivity to metrical structure in music, and oscillatory activity in relation to both rhythm and reading we stand to identify the biological mechanisms they share. Our expertise in auditory neurophysiology enables us to provide unique insight into the rhythm-reading link by providing objective neural measures of auditory processing. Our objective is to understand the link between central auditory processing, rhythmic synchronization, and pre-reading skills during early childhood. Our central hypothesis is that neural timing and synchrony in the auditory system provide overlapping support to rhythmic synchronization and language performance. Given the dearth of research on this topic though, we can only begin to speculate as to which aspects of rhythmic synchronization and reading overlap. Nevertheless, we see this as an important topic with the potential to change our understanding of the biology of reading development. We will accomplish our objective by pursuing two specific aims and testing the accompanying hypotheses: 1. Determine how early language skills are linked to a child’s synchronization ability. The working hypothesis is that children with superior rhythmic synchronization abilities have stronger phonological processing and associated reading readiness skills. 2. Identify the shared biological mechanisms underlying synchronization ability and pre-reading skills during early childhood. The working hypothesis is that the fine temporal precision is a chief mechanism required for both rhythm and reading is provided by precise timing in the auditory system, and this explains their relationship. An understanding of the shared neural mechanisms underlying rhythm and reading can inform the design of biologically inspired assessment and interventions. An exciting possibility is that this work can lead to targeted rhythm-based interventions and therapies that would support language skills as children begin to read. This work will allow unprecedented insight into the role rhythm plays in a child's language development and, by extension, the biological foundations of reading.