Authors: Hornickel, Jane; Nina Kraus.
Publication: Journal of Neuroscience 33 (8) 3500-3504 2013 | DOI: 10.1523/JNEUROSCI.4205-12.2013
Learning to read proceeds smoothly for most children, yet others struggle to translate verbal language into its written form. Poor readers often have a host of auditory, linguistic, and attention deficits, including abnormal neural representation of speech and inconsistent performance on psychoacoustic tasks. We hypothesize that this constellation of deficits associated with reading disorders arises from the human auditory system failing to respond to sound in a consistent manner, and that this inconsistency impinges upon the ability to relate phonology and orthography during reading. In support of this hypothesis, we show that poor readers have significantly more variable auditory brainstem responses to speech than do good readers, independent of resting neurophysiological noise levels. Thus, neural variability may be an underlying biological contributor to well established behavioral and neural deficits found in poor readers.
Overall, our results suggest that neural inconsistency in response to sound is a biological mechanism that may contribute to reading impairment.
Here we demonstrate that children who are poor readers have more variable neural responses to speech, reflecting an inconsistency in the brain’s response to sound from trial-to-trial. While we cannot determine whether auditory brainstem variability was present since birth in our participants, it is likely that initial variability in speech sound representations led to weaker phonological development in the preschool years, and weaker phonological development failed to tune the auditory system to selectively represent meaningful speech sound differences as being important. Children with reading difficulties appear to be more sensitive to perceiving and encoding nonmeaningful speech contrasts than their typically developing peers …
Here we provide evidence that poor readers have less stable auditory nervous system function than do good readers, a relationship that is not mediated by participant factors such as age, sex, attention, IQ, and socioeconomic status. Although causality cannot be determined, heightened variability in nervous system function may underlie fluctuations in directed attention and impaired speech understanding due to inconsistent encoding. Our results suggest that good readers profit from a stable neural representation of sound, and that children who have inconsistent neural responses are likely at a disadvantage when learning to read. Encouragingly, response consistency can be improved with auditory training, particularly for children with the most variable responses before training….