Impaired Perception and Neural Processing of Rules in Developmental Dyslexia

Sensory intelligence for extraction of abstract auditory rules from a speech sound stream in children with cochlear implants

OBJECTIVE

Sensory intelligence in the brain helps listeners automatically extract abstract auditory rules formed by invariant acoustic features from complex speech sound streams, presumably serving as the neural basis for speech comprehension. However, whether this intelligence is deficient in children with cochlear implants (CIs) remains unclear.

METHODS

Mandarin Chinese monosyllables shared a flat lexical tone contour to form an abstract auditory rule but differed in other acoustic features to construct a complex speech sound stream. The abstract rule was occasionally violated by monosyllables with a rising or falling lexical tone.

RESULTS

In normal hearing (NH) children, the abstract auditory rule could be extracted, as revealed by a mismatch negativity (MMN) and a late discriminative negativity (LDN). However, the MMN and LDN were only evoked in CI children with good hearing and speech performance. NH children with a higher speech perception or spatial hearing score had a greater MMN. The LDN was attenuated with increasing age in NH children.

CONCLUSIONS

The sensory intelligence for extraction of auditory abstract rules, associated with speech perception, is deficient in CI children. This intelligence may gradually develop during childhood and adolescence.

SIGNIFICANCE

Deficient sensory intelligence in CI children may aid in understanding poor speech comprehension in complex environments.

Neural correlates of statistical learning in developmental dyslexia: An electroencephalography study

The human brain extracts statistical regularities from the surrounding environment in a process called statistical learning. Behavioural evidence suggests that developmental dyslexia affects statistical learning. However, surprisingly few studies have assessed how developmental dyslexia affects the neural processing underlying this type of learning. We used electroencephalography to explore the neural correlates of an important aspect of statistical learning - sensitivity to transitional probabilities - in individuals with developmental dyslexia. Adults diagnosed with developmental dyslexia (n = 17) and controls (n = 19) were exposed to a continuous stream of sound triplets. Every so often, a triplet ending had a low transitional probability given the triplet's first two sounds ("statistical deviants"). Furthermore, every so often a triplet ending was presented from a deviant location ("acoustic deviants"). We examined mismatch negativity elicited by statistical deviants (sMMN), and MMN elicited by location deviants (i.e., acoustic changes). Acoustic deviants elicited a MMN which was larger in the control group than in the developmental dyslexia group. Statistical deviants elicited a small, yet significant, sMMN in the control group, but not in the developmental dyslexia group. However, the difference between the groups was not significant. Our findings indicate that the neural mechanisms underlying pre-attentive acoustic change detection and implicit statistical auditory learning are both affected in developmental dyslexia.

Rethinking Literacy Intervention: Addressing a Practice Gap With Best Practices From Multisensory Structured Language Approaches

PURPOSE

Dyslexia is increasingly being defined, assessed, diagnosed, and treated in the educational system. The purpose of this clinical focus article is to elucidate ways in which speech-language pathologists (SLPs) can rethink how to implement literacy interventions to incorporate best practices from multisensory structured language (MSL) approaches and how they can be influential participants in the conversations of how to define and implement services for students who have written language disorders, including dyslexia, in the school setting.

METHOD

This clinical focus article provides an operational definition of dyslexia, discusses the various roles and responsibilities of SLPs with respect to dyslexia, and describes the well-established evidence-based practices of MSL approaches as a means of rethinking literacy intervention.

RESULTS

Using a case study scenario based on an individual diagnosed with dyslexia, this clinical focus article presents similarities and differences between traditional speech-language pathology intervention approaches and MSL approaches to literacy intervention.

CONCLUSIONS

MSL strategies may be considered in literacy intervention as a means to optimize the academic gains of children with dyslexia in a school setting. Furthermore, SLPs should be considered integral participants in discussions of policies and practices related to the diagnosis and treatment of literacy disorders, including dyslexia.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.23228483.

Neural phoneme discrimination in variable speech in newborns - Associations with dyslexia risk and later language skills

A crucial skill in infant language acquisition is learning of the native language phonemes. This requires the ability to group complex sounds into distinct auditory categories based on their shared features. Problems in phonetic learning have been suggested to underlie language learning difficulties in dyslexia, a developmental reading-skill deficit. We investigated auditory abilities important for language acquisition in newborns with or without a familial risk for dyslexia with electrophysiological mismatch responses (MMRs). We presented vowel changes in a sequence of acoustically varying vowels, requiring grouping of the stimuli to two phoneme categories. The vowel changes elicited an MMR which was significantly diminished in infants whose parents had the most severe dyslexia in our sample. Phoneme-MMR amplitude and its hemispheric lateralization were associated with language test outcomes assessed at 28 months, an age at which it becomes possible to behaviourally test children and several standardized tests are available. In addition, statistically significant MMRs to violations of a complex sound-order rule were only found in infants without dyslexia risk, but these results are very preliminary due to small sample size. The results demonstrate the relevance of the newborn infants' readiness for phonetic learning for their emerging language skills. Phoneme extraction difficulties in infants at familial risk may contribute to the phonological deficits observed in dyslexia.