Prenatal sensory development

Peer reviewe

The neural basis of speech sound discrimination from infancy to adulthood

Rapid processing of speech is facilitated by neural representations of native language phonemes. However, some disorders and developmental conditions, such as developmental dyslexia, can hamper the development of these neural memory traces, leading to language delays and poor academic achievement. While the early identification of such deficits is paramount so that interventions can be started as early as possible, there is currently no systematically used ecologically valid paradigm for the assessment of the neural basis of speech sound processing. Thus, this thesis investigates the feasibility of a mismatch negativity (MMN) paradigm presenting speech sounds embedded in pseudo words to probe the neural discrimination accuracy of sounds in more natural context. Furthermore, the applicability of this paradigm for infant research was determined in a study investigating the effects of additional prenatal speech stimulation on newborn sound processing. The results show, on group level, that while healthy adults neurally detect all speech sound changes used in the experiments, the 4-12 -year-old children s and infants neural processing of speech sounds varies with age. In particular, the preschool children seem to be more proficient in neurally detecting small pitch changes in word context than school-aged children. Furthermore, children s MMNs were found to be associated with improved verbal IQ 14-17 months later, while the positively-displaced MMN, the p-MMR, correlated with poorer performance IQ. The results on the effects of additional prenatal exposure to pitch-modulated speech sounds showed that the MMNs to pitch changes in pseudo words were enhanced after birth, indicating specific learning effects due to additional prenatal stimulation. Furthermore, these learning effects generalized to other types of speech sounds not included in the learning material. Taken together, these findings suggest that the paradigm presenting speech sound changes in word context is viable for probing the neural memory traces for speech sounds from infancy to adulthood. The possibility to assess neural speech sound discrimination broadly in a single EEG recording could be used, for example, to classify between different subtypes of dyslexia. Finally, the neural effects induced by fetal learning suggest that prenatal exposure to sounds, for example, to the voice of the mother, may predispose the infant to be neurally sensitive to such sounds by birth.Puheen ymmärtäminen perustuu osin oman äidinkielen puheäänteille muodostuneisiin hermostollisiin muistijälkiin. Jotkin oireyhtymät tai kehitykselliset häiriöt, kuten lukihäiriö, voivat kuitenkin haitata näiden muistijälkien muodostumista. Tämä voi ilmetä esimerkiksi kielen kehityksen viivästyminä tai huonona koulumenestyksenä. Kuntoutuksen kannalta kielenkehityksen vaikeuksien varhainen tunnistaminen on tärkeää, mutta systemaattisesti käytettyä ja luonnollisen kaltaista ääniympäristöä jäljittelevää asetelmaa puheen piirteiden hermostollisen perustan tutkimiseen ei ole. Tässä tutkimuksessa selvitettiin, soveltuuko puheäänteiden muutoksia sanakontekstissa mismatch negativity (MMN) -vasteen avulla mittaava monipiirreasetelma äänten hermostollisten muistijälkien ja sikiöaikaisen kuuloaineksen oppimisen hermostollisten vaikutusten tarkasteluun. Ryhmätason tulosten perusteella terveiden aikuisten aivot tunnistivat puheen piirteiden muutokset, mutta 4-12 -vuotiaiden lasten ja vauvojen aivot käsittelivät puheen piirteiden muutoksia eri tavoin. Esimerkiksi esikouluikäisten kuulojärjestelmä vaikutti käsittelevän sanakontekstissa esitettyjen äänen korkeuksien muutoksia tarkemmin kuin kouluikäisten. 4 12 -vuotiailla lapsilla suuremmat MMN-vasteet olivat myös yhteydessä parempaan kielelliseen päättelysuoriutumiseen, ja MMN:n positiivinen muoto, p-MMR, oli yhteydessä heikompaan näönvaraiseen päättelysuoriutumiseen 14-17 kuukautta myöhemmin. Tutkimus osoitti myös, että sikiöaikainen altistus puheäänten taajuusmuutoksille vahvisti vauvojen aivojen kykyä erotella puheen taajuusmuutoksia. Sikiöaikaisen altistuksen myötä vauvojen kuulojärjestelmä oppi myös erottamaan muutoksia, joille vauvat eivät olleet altistuneet raskauden aikana ja joita äänimateriaalille altistamattomat vauvat eivät kyenneet erottelemaan. Kokonaisuudessaan tulokset osoittivat, että väitöskirjan tutkimuksissa testattu MMN-asetelma soveltuu puheen piirteiden hermostollisten muistijälkien tutkimukseen ryhmätasolla vauvoista aikuisiin. Useiden erityyppisten puheäänten muutosten hermostollisen erottelukyvyn tutkiminen samanaikaisesti voi hyödyttää esimerkiksi erilaisten lukihäiriötyyppien erottelua. Havaitut sikiöaikaisen oppimisen hermostolliset vaikutukset viittaavat siihen, että sikiöaikainen altistus esimerkiksi äidin äänelle voi edesauttaa samankaltaisten äänien hermostollista käsittelyä syntymän jälkeen

Larp-Related Stress

Non peer reviewe

Can very early music interventions promote at-risk infants’ development?

Music and musical activities are often a natural part of parenting. As accumulating evidence shows, music can promote auditory and language development in infancy and early childhood. It may even help to support auditory and language skills in infants whose development is compromised by heritable conditions, like the reading deficit dyslexia, or by environmental factors, such as premature birth. For example, infants born to dyslexic parents can have atypical brain responses to speech sounds and subsequent challenges in language development. Children born very preterm, in turn, have an increased likelihood of sensory, cognitive, and motor deficits. To ameliorate these deficits, we have developed early interventions focusing on music. Preliminary results of our ongoing longitudinal studies suggest that music making and parental singing promote infants' early language development and auditory neural processing. Together with previous findings in the field, the present studies highlight the role of active, social music making in supporting auditory and language development in at-risk children and infants. Once completed, the studies will illuminate both risk and protective factors in development and offer a comprehensive model of understanding the promises of music activities in promoting positive developmental outcomes during the first years of life.Peer reviewe

Neural discrimination of speech sound changes in a variable context occurs irrespective of attention and explicit awareness

To process complex stimuli like language, our auditory system must tolerate large acoustic variance, like speaker variability, and still be sensitive enough to discriminate between phonemes and to detect complex sound relationships in, e.g., prosodic cues. Our study determined discrimination of speech sounds in input mimicking natural speech variability, and detection of deviations in regular pitch relationships (rule violations) between speech sounds. We investigated the automaticity and the influence of attention and explicit awareness on these changes by recording the neurophysiological mismatch negativity (MMN) and P3a as well as task performance from 21 adults. The results showed neural discrimination of phonemes and rule violations as indicated by MMN and P3a, regardless of whether the sounds were attended or not, even when participants could not explicitly describe the rule. While small sample size precluded statistical analysis of some outcomes, we still found preliminary associations between the MMN amplitudes, task performance, and emerging explicit awareness of the rule. Our results highlight the automaticity of processing complex aspects of speech as a basis for the emerging conscious perception and explicit awareness of speech properties. While MMN operates at the implicit processing level, P3a appears to work at the borderline of implicit and explicit.Peer reviewe

Formation of neocortical memory circuits for unattended written word forms : neuromagnetic evidence

To master linguistic communication, humans must acquire large vocabularies quickly and effortlessly. Efficient word learning might be facilitated by the ability to rapidly acquire novel word forms even outside the focus of attention, occurring within minutes of repetitive exposure and suggesting fast and automatic lexicon acquisition. However, this phenomenon has been studied in the auditory modality only, and it is unknown whether similar mechanisms also exist in the visual domain. We tested this by presenting participants with novel written word forms while the focus of their attention was on a non-linguistic dual colour-detection task. Matched familiar word forms served as a control. Using magnetoencephalography (MEG), we scrutinised changes in neuromagnetic responses to familiar and to novel word forms over approximately 15 minutes of exposure. We found, for the first time, a visual analogue of automatic rapid build-up of neural memory circuits for unattended novel lexical items, seen as a rapid enhancement of early (similar to 100 ms post-onset) activation in the left anterior-superior temporal lobe. Our results suggest that the brain quickly forms cortical representations for new written forms, and indicate that the automatic neural mechanisms subserving rapid online acquisition of novel linguistic information might be shared by both auditory and visual modalities.Peer reviewe

Musical perceptual skills, but not neural auditory processing, are associated with better reading ability in childhood

Musical activities have been suggested to be beneficial for language development in childhood. Randomised controlled trials using music have indicated that musical interventions can be used to support language skills in children with developmental language difficulties. However, it is not entirely clear how beneficial music activities are for normally developing children or how the effects mediated via music are transmitted. To investigate these questions, the present study used structural equation models to assess how musical training, perceptual musical skills, and auditory processing in the brain are associated with reading proficiency and each other. Perceptual musical skills were assessed using musicality tests while auditory processing in the brain was measured using mismatch negativity responses to pitch, duration, and phoneme length contrasts. Our participants were a community sample of 64 8–11-year-old typically developing children with and without musical training, recruited from four classes in four elementary schools in Finland. Approximately half of children had music as a hobby. Our results suggest that performance in tests of musical perceptual skills is directly linked with reading proficiency instead of being mediated via auditory processing in the brain. Auditory processing in the brain in itself seems not to be strongly linked with reading proficiency in these children. Our results support the view that musical perceptual skills are associated with reading skills regardless of musical training.Peer reviewe

Newborn infants' auditory system is sensitive to Western music chord categories

Neural encoding of abstract rules in the audition of newborn infants has been recently demonstrated in several studies using event-related potentials (ERPs). In the present study the neural encoding of Western music chords was investigated in newborn infants. Using ERPs, we examined whether the categorizations of major vs. minor and consonance vs. dissonance are present at the level of the change-related mismatch response (MMR). Using an oddball paradigm, root minor, dissonant and inverted major chords were presented in a context of consonant root major chords. The chords were transposed to several different frequency levels, so that the deviant chords did not include a physically deviant frequency that could result in an MMR without categorization. The results show that the newborn infants were sensitive to both dissonant and minor chords but not to inverted major chords in the context of consonant root major chords. While the dissonant chords elicited a large positive MMR, the minor chords elicited a negative MMR. This indicates that the two categories were processed differently. The results suggest newborn infants are sensitive to Western music categorizations, which is consistent with the authors' previous studies in adults and school-aged children.Peer reviewe

Learning-induced neural plasticity of speech processing before birth

Peer reviewe

Auditory event-related potentials at preschool age in children born very preterm.

To assess auditory event-related potentials at preschool age in children born very preterm (VP, 27.4±1.9 gestational weeks, n=70) with a high risk of cognitive dysfunction