Paula Virtala

Developmental dyslexia (DD) is a heritable reading disorder characterized by phonological deficits. Still, the mechanisms through which genetic susceptibility influence early literacy development and speech sound processing remain unclear. This longitudinal study investigated associations between DD susceptibility genes and the development of pre-reading skills and neural speech discrimination between two and five years of age. We studied 159 children, most with familial risk of DD. Genetic susceptibility to DD was determined through six single nucleotide variants in the genes DYX1C1, DCDC2, KIAA0319, ROBO1, NCAN, and NRSN1, as well as an unweighted polygenic risk score across these variants capturing cumulative genetic burden. Pre-reading skills were assessed using a behavioral test battery, whereas neural speech discrimination was studied by recording event-related potentials to speech-sound changes.Individual genetic variants were associated with pre-reading abilities already at two years. Variants in DCDC2 and ROBO1 were linked to serial naming, whereas variants in DYX1C1, NRSN1, and ROBO1 were associated with auditory short-term memory. Variants in NCAN and DCDC2 were associated with reduced mismatch negativity (MMN) amplitudes at both two and five years. A higher polygenic risk was associated with reduced MMN and late discriminative negativity amplitudes at two years. Overall, this study suggests that genetic susceptibility mediated by at least five of the identified DD susceptibility genes influences both neural speech processing and cognitive precursors of reading since early childhood. It supports the view that DD is a neurodevelopmental condition with early-emerging biological signatures, and highlights mismatch responses as a potential neurophysiological endophenotype for DD.

Background: Infancy and early childhood lay the foundation for language and reading abilities. They are crucial for success in social relationships, education, and work life, but can be compromised by heritable conditions such as developmental dyslexia. Music activities have shown associations with auditory, language, and literacy skills, but randomized controlled trials (RCTs) have been lacking, especially in young and at-risk populations. This two-arm RCT evaluates the efficacy of an early music intervention for language development. As highly novel aspects, we investigate whether and how the efficacy is influenced by familial dyslexia risk and its genetic markers, as well as intervention timing (children’s age and developmental status), and mediated by expected social–emotional benefits of the interventions on the parent, child, and their interaction. Methods: A maximum of 200 infants will be recruited for the trial, with approximately 50% of them at familial dyslexia risk, and randomized to the experimental (music intervention) or control arm (circus intervention), where they will start a weekly 6-month intervention at the age of approximately 8–12 months. Outcome measures will be evaluated at baseline, at 6 months (after the intervention), and at a 1-year follow-up (1.5 years from the baseline). As primary outcome measures of language development, language abilities will be evaluated with standardized parental questionnaires (validated parental report instruments) and neural speech processing with auditory event-related potentials. Further outcome measures include, for example, standardized tests of language development, standardized parental questionnaires on social–emotional factors, neural processing of music, questionnaires and standardized tests of motor development, and dyslexia genetics (DNA sampling). Discussion: The present trial is expected to fill significant gaps in previous research on the effects of early-age musical activities on language development. By comparing a musical intervention to an equally active, social, structured, and pleasurable circus intervention in a randomized, controlled setting with pre- and post-assessments, the unique benefits of musical activities can be probed reliably. The trial can provide completely novel information on the moderators and mediators of the intervention outcomes, including participant characteristics such as dyslexia risk, age, and developmental stage, as well as social–emotional benefits of pleasurable group activities. Clinical trial registration: ClinicalTrials.gov ; identifier NCT06261307.

Developmental dyslexia is associated with deficient temporal auditory processing, which may play an important role in speech perception, language development, and subsequently, learning to read. Music activities may offer a way to support temporal auditory processing and language and reading development. We utilized change‐related mismatch negativities (MMNs) of the electroencephalogram (EEG) to study the detection of temporal pattern violations in tone sequences in 28‐month‐olds, and its associations with dyslexia risk, language skills, and music activities. We also considered possible effects of two infant music‐listening interventions. The MMN had diminished amplitudes in dyslexia risk compared to control children in the left hemisphere, and left‐hemisphere dominance was only seen in the controls. Larger MMNs were associated with better language skills and higher amount of parent‐reported shared music activities, but not with the infant music‐listening interventions. The results demonstrate, in line with our hypotheses, deficient processing of temporal patterns in tone sequences in familial dyslexia‐risk children. Together with the positive association with language skills, this supports the relevance of temporal auditory processing for language and reading development. The association of MMNs with the frequency of shared music activities at home suggests that active, joint music making might benefit temporal auditory processing.

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. Research highlights We recorded mismatch responses (MMRs) to vowel changes in a variable speech stream Newborns extracted relevant phonetic information from the stream, evidenced by MMRs High dyslexia risk infants had diminished MMRs to vowel changes MMR amplitudes and hemispheric lateralization correlated with later language skills Poor phoneme extraction may compromise phonological and language development

Rules and regularities of language are typically processed in an implicit and effortless way in the human brain. Individuals with developmental dyslexia have problems in implicit learning of regularities in sequential stimuli, but the neural basis of this deficit has not been studied. This study investigated extraction and utilization of a complex auditory rule at neural and perceptual levels in 18 adults with dyslexia and 20 typical readers. Mismatch negativity (MMN) and P3a responses to rule violations in speech stimuli, reflecting change detection and attention switch, respectively, were recorded with electroencephalogram. Both groups reported no or little explicit awareness of the rule, suggesting implicit processing. People with dyslexia showed deficient extraction of the rule evidenced by diminished MMNs estimated to originate particularly from the left perisylvian region. The group difference persisted in the attentive condition after the participants were told about the rule, and behavioral detection of the rule violations was poor in people with dyslexia, possibly suggesting difficulties also in utilizing explicit information of the rule. Based on these results, the speech processing difficulties in dyslexia extend beyond phoneme discrimination and basic auditory feature extraction. Challenges in implicit extraction and effortless adoption of complex auditory rules may be central to language learning difficulties in dyslexia.