Healthy full-term infants' brain responses to emotionally and linguistically relevant sounds using a multi-feature mismatch negativity (MMN) paradigm

Understanding the neural mechanisms for infants' perception of native and non-native speech

Though perceptual narrowing has been widely recognized as a process guiding cognitive development and category learning in infancy and early childhood, its neural mechanisms and traits at a cortical level remain unclear. Using an electroencephalography (EEG) abstract mismatch negativity (MMN) paradigm, Australian infants' neural sensitivity to (native) English and (non-native) Nuu-Chah-Nulth speech contrasts was examined in a cross-sectional design at the onset (5-6 months) and offset (11-12 months) of perceptual narrowing. Immature mismatch responses (MMR) were observed among younger infants for both contrasts, while older infants showed MMR response to the non-native contrast, and both MMR and MMN to the native contrast. Sensitivity to the Nuu-Chah-Nulth contrast at perceptual narrowing offset was retained yet stayed immature. Findings conform to perceptual assimilation theories, reflecting plasticity in early speech perception and development. Compared to behavioural paradigms, neural examination effectively reveals experience-induced processing differences to subtle contrasts at the offset of perceptual narrowing.

Multi-feature mismatch negativity: How can reliable data be recorded in a short time?

OBJECTIVE

The aim of the study was to conduct multi-feature mismatch negativity (MMN) implementations and identify via a test-retest study the reliability of MMN responses obtained through a 5-stimulus version of the MMN paradigm. It was also aimed to identify a reliable MMN recording number by comparing the MMN responses obtained under conditions of ten and four recordings conditions while making the recording time shorter.

METHODS

Twenty-one healthy volunteers, aged between 18 and 36 years, were included in the study. A 5-stimulus version of the multi-feature MMN paradigm was presented to participants. Ten recordings were obtained for each participant under both test and retest conditions. The MATLAB program was utilized in the evaluation of MMN amplitude and latency. The Fz was chosen for the statistical analysis. Four of the ten recordings were chosen at random, and statistical analyses were performed again for those four recordings.

RESULTS

There was no statistically significant difference in amplitudes obtained from test and retest conditions with ten recordings. With four recordings, for frequency, intensity, duration, and gap deviants, there were no statistically significant differences between amplitudes obtained under test and retest conditions. However, there was a statistically significant difference between amplitudes of the location deviant. No statistically significant difference was observed among latencies under test-retest conditions with both ten and four recordings.

CONCLUSIONS

These findings demonstrate that MMN amplitudes could be used reliably as short-time evaluations with four recordings, but more recordings are required for MMN latencies. In terms of practicality, four recordings are more advantageous and comfortable for both clinicians and patients in MMN practice.

SIGNIFICANCE

When behavioral tests are required, MMN is regarded as an objective test that can be used reliably for adults, children, and infants who cannot be evaluated using behavioral methods. It is concluded that conditions with four recordings aremore advantageous and comfortable for both clinicians and patients in MMN practice.

Auditory Mismatch Responses to Emotional Stimuli in 3-Year-Olds in Relation to Prenatal Maternal Depression Symptoms

Maternal depression symptoms are common in pregnant women and can have negative effects on offspring’s emotional development. This study investigated the association between prenatal maternal depression symptoms (assessed with the Edinburgh Postnatal Depression Scale at 24 weeks of gestation) and auditory perception of emotional stimuli in 3-year-olds (n = 58) from the FinnBrain Birth Cohort Study. Using electroencephalography (EEG), we examined mismatch responses for happy, sad, and angry sounds presented among neutral stimuli. A positive association between maternal depression symptoms and the emotional mismatch responses in an early time window (80–120 ms) was found, indicating that brain responses of children of mothers with depressive symptoms were weaker to happy sounds, though the results did not survive Bonferroni correction. There were no clear associations in the sad and angry emotional categories. Our results tentatively support that the 3-year-old children of mothers with depression symptoms may be less sensitive to automatically detect happy sounds compared to children whose mothers do not display symptoms of depression.

Relevance to the higher order structure may govern auditory statistical learning in neonates

Hearing is one of the earliest senses to develop and is quite mature by birth. Contemporary theories assume that regularities in sound are exploited by the brain to create internal models of the environment. Through statistical learning, internal models extrapolate from patterns to predictions about subsequent experience. In adults, altered brain responses to sound enable us to infer the existence and properties of these models. In this study, brain potentials were used to determine whether newborns exhibit context-dependent modulations of a brain response that can be used to infer the existence and properties of internal models. Results are indicative of significant context-dependence in the responsivity to sound in newborns. When common and rare sounds continue in stable probabilities over a very long period, neonates respond to all sounds equivalently (no differentiation). However, when the same common and rare sounds at the same probabilities alternate over time, the neonate responses show clear differentiations. The context-dependence is consistent with the possibility that the neonate brain produces more precise internal models that discriminate between contexts when there is an emergent structure to be discovered but appears to adopt broader models when discrimination delivers little or no additional information about the environment.

Repeated Parental Singing During Kangaroo Care Improved Neural Processing of Speech Sound Changes in Preterm Infants at Term Age

Preterm birth carries a risk for adverse neurodevelopment. Cognitive dysfunctions, such as language disorders may manifest as atypical sound discrimination already in early infancy. As infant-directed singing has been shown to enhance language acquisition in infants, we examined whether parental singing during skin-to-skin care (kangaroo care) improves speech sound discrimination in preterm infants. Forty-five preterm infants born between 26 and 33 gestational weeks (GW) and their parents participated in this cluster-randomized controlled trial (ClinicalTrials ID IRB00003181SK). In both groups, parents conducted kangaroo care during 33-40 GW. In the singing intervention group (n = 24), a certified music therapist guided parents to sing or hum during daily kangaroo care. In the control group (n = 21), parents conducted standard kangaroo care and were not instructed to use their voices. Parents in both groups reported the duration of daily intervention. Auditory event-related potentials were recorded with electroencephalogram at term age using a multi-feature paradigm consisting of phonetic and emotional speech sound changes and a one-deviant oddball paradigm with pure tones. In the multi-feature paradigm, prominent mismatch responses (MMR) were elicited to the emotional sounds and many of the phonetic deviants in the singing intervention group and in the control group to some of the emotional and phonetic deviants. A group difference was found as the MMRs were larger in the singing intervention group, mainly due to larger MMRs being elicited to the emotional sounds, especially in females. The overall duration of the singing intervention (range 15-63 days) was positively associated with the MMR amplitudes for both phonetic and emotional stimuli in both sexes, unlike the daily singing time (range 8-120 min/day). In the oddball paradigm, MMRs for the non-speech sounds were elicited in both groups and no group differences nor connections between the singing time and the response amplitudes were found. These results imply that repeated parental singing during kangaroo care improved auditory discrimination of phonetic and emotional speech sounds in preterm infants at term age. Regular singing routines can be recommended for parents to promote the development of the auditory system and auditory processing of speech sounds in preterm infants.

The effect of lexical status on prosodic processing in infants learning a fixed stress language

In speech processing, in the first year of life, prosody and phoneme-relevant aspects serve different functions. Recent studies have assumed that the two aspects become integrated at around 9 months of age. The present study investigates the effect of lexical status on stress processing in a fixed stress language. We hypothesize that lexicality modulates stress processing, and where the stress cue is in conflict with the lexical status (legal deviant condition), we will observe differences in age indicating the stage of integration. We tested 69 6 and 10 month-old infants in an acoustic oddball event-related potential paradigm. A frequent word stimulus (baba) and a pseudoword (bebe) were used with legal versus illegal stress. We systematically swapped the standard and deviant roles of the different stress variants in two conditions. In the illegal deviant condition in the case of the word stimulus, the response pattern typical for the pseudoword (an MMR to the absence of the stress cue) was missing. This implies the suppression effect of lexicality. In the legal deviant condition, negative MMR (N-MMR) in the second time window indicated a facilitation effect of lexicality in both age groups. As only the 6-month-olds produced an N-MMR in the first time window, we concluded that in a fixed stress language, integration starts at 6 months but is only completed by the age of 10 months. Our results show that lexical status modulates stress processing at word level in a highly regularly stressed language in which stable, long-term language-specific stress representation exists from early infancy.

Maternal sleep quality during pregnancy is associated with neonatal auditory ERPs

Poor maternal sleep quality during pregnancy may act as a prenatal stress factor for the fetus and associate with neonate neurocognition, for example via fetal programming. The impacts of worsened maternal sleep on neonatal development and, more specifically on neonatal auditory brain responses, have not been studied. A total of 155 mother-neonate dyads drawn from the FinnBrain Birth Cohort Study participated in our study including maternal self-report questionnaires on sleep at gestational week 24 and an event-related potential (ERP) measurement among 1-2-day-old neonates. For sleep quality assessment, the Basic Nordic Sleep Questionnaire (BNSQ) was used and calculated scores for (1) insomnia, (2) subjective sleep loss and (3) sleepiness were formed and applied in the analyses. In the auditory ERP protocol, three emotionally uttered pseudo words (in happy, angry and sad valence) were presented among neutrally uttered pseudo words. To study the relations between prenatal maternal sleep quality and auditory emotion-related ERP responses, mixed-effects regression models were computed for early (100–200 ms) and late (300–500 ms) ERP response time-windows. All of the selected BNSQ scores were associated with neonatal ERP responses for happy and angry emotion stimuli (sleep loss and sleepiness in the early, and insomnia, sleep loss and sleepiness in the late time-window). For sad stimuli, only maternal sleep loss predicted the neonatal ERP response in the late time-window, likely because the overall ERP was weakest in the sad condition. We conclude that maternal sleep quality during pregnancy is associated with changes in neonatal auditory ERP responses.

Prenatal exposure to antiepileptic drugs and early processing of emotionally relevant sounds

INTRODUCTION

Prenatal exposure to antiepileptic drugs (AEDs) is associated with developmental compromises in verbal intelligence and social skills in childhood. Our aim was to evaluate whether a multifeature Mismatch Negativity (MMN) paradigm assessing semantic and emotional components of linguistic and emotional processing would be useful to detect possible alterations in early auditory processing of newborns with prenatal AED exposure.

MATERIAL AND METHODS

Data on AED exposure, pregnancy outcome, neuropsychological evaluation of the mothers, information on maternal epilepsy type, and a structured neurological examination of the newborn were collected prospectively. Blinded to AED exposure, we compared a cohort of 36 AED-exposed with 46 control newborns at the age of two weeks by measuring MMN with a multifeature paradigm with six linguistically relevant deviant sounds and three emotionally uttered sounds.

RESULTS

Frontal responses for the emotionally uttered stimulus Happy differed significantly in the exposed newborns compared with the control newborns. In addition, responses to sounds with or without emotional component differed in newborns exposed to multiple AEDs compared with control newborns or to newborns exposed to only one AED.

CONCLUSIONS

These preliminary findings suggest that prenatal AED exposure may alter early processing of emotionally and linguistically relevant sound information.

Maturation of Speech-Sound ERPs in 5-6-Year-Old Children: A Longitudinal Study

The maturation of 5-6-year-old children's auditory discrimination - indicated by the development of the auditory event-related-potentials (ERPs) - has not been previously studied in longitudinal settings. For the first time, we present here the results based on extensive dataset collected from 75 children. We followed the 5- to 6-year-olds for 20 months and measured their ERPs four times with the same multifeature paradigm with phonemic stimuli. The amplitude of the mismatch negativity (MMN) response increased during this time for vowel, vowel duration and frequency changes. Furthermore, the P3a component started to mature toward adult-like positivity for the vowel, intensity and frequency deviants and the late discriminative negativity (LDN) component decreased with age for vowel and intensity deviants. All the changes in the components seemed to happen during the second follow-up year, when Finnish children are taught letter symbols and other preliminary academic skills before going to school at the age of seven. Therefore, further studies are needed to clarify if these changes in the auditory discrimination are purely age-related or due to increasing linguistic knowledge of the children.