Fetal audition

A Review on the Vagus Nerve and Autonomic Nervous System During Fetal Development: Searching for Critical Windows

The autonomic nervous system (ANS) is one of the main biological systems that regulates the body's physiology. Autonomic nervous system regulatory capacity begins before birth as the sympathetic and parasympathetic activity contributes significantly to the fetus' development. In particular, several studies have shown how vagus nerve is involved in many vital processes during fetal, perinatal, and postnatal life: from the regulation of inflammation through the anti-inflammatory cholinergic pathway, which may affect the functioning of each organ, to the production of hormones involved in bioenergetic metabolism. In addition, the vagus nerve has been recognized as the primary afferent pathway capable of transmitting information to the brain from every organ of the body. Therefore, this hypothesis paper aims to review the development of ANS during fetal and perinatal life, focusing particularly on the vagus nerve, to identify possible "critical windows" that could impact its maturation. These "critical windows" could help clinicians know when to monitor fetuses to effectively assess the developmental status of both ANS and specifically the vagus nerve. In addition, this paper will focus on which factors-i.e., fetal characteristics and behaviors, maternal lifestyle and pathologies, placental health and dysfunction, labor, incubator conditions, and drug exposure-may have an impact on the development of the vagus during the above-mentioned "critical window" and how. This analysis could help clinicians and stakeholders define precise guidelines for improving the management of fetuses and newborns, particularly to reduce the potential adverse environmental impacts on ANS development that may lead to persistent long-term consequences. Since the development of ANS and the vagus influence have been shown to be reflected in cardiac variability, this paper will rely in particular on studies using fetal heart rate variability (fHRV) to monitor the continued growth and health of both animal and human fetuses. In fact, fHRV is a non-invasive marker whose changes have been associated with ANS development, vagal modulation, systemic and neurological inflammatory reactions, and even fetal distress during labor.

Perinatal attention, memory and learning during sleep

The perinatal brain is well equipped to react to the environment during sleep. Several lines of research in animals and humans prior to and immediately after birth have documented the capability to respond, to process and remember patterns of stimulation. In this article, we will summarize recent findings as well as previous work documenting the memory and learning capacities of the developing brain during sleep and wake states. The role of these sleep state dependent processes may play in the ability to adapt to the postnatal environment will be discussed.

Impact of prematurity on neurodevelopment

The consequences of prematurity on brain functional development are numerous and diverse, and impact all brain functions at different levels. Prematurity occurs between 22 and 36 weeks of gestation. This period is marked by extreme dynamics in the physiologic maturation, structural, and functional processes. These different processes appear sequentially or simultaneously. They are dependent on genetic and/or environmental factors. Disturbance of these processes or of the fine-tuning between them, when caring for premature children, is likely to induce disturbances in the structural and functional development of the immature neural networks. These will appear as impairments in learning skills progress and are likely to have a lasting impact on the development of children born prematurely. The level of severity depends on the initial alteration, whether structural or functional. In this chapter, after having briefly reviewed the neurodevelopmental, structural, and functional processes, we describe, in a nonexhaustive manner, the impact of prematurity on the different brain, motor, sensory, and cognitive functions.

Preparing for Life After Birth: Introducing the Concepts of Intrauterine and Extrauterine Sensory Entrainment in Mammalian Young

Presented is an updated understanding of the development of sensory systems in the offspring of a wide range of terrestrial mammals, the prenatal exposure of those systems to salient stimuli, and the mechanisms by which that exposure can embed particular sensory capabilities that prepare newborns to respond appropriately to similar stimuli they may encounter after birth. Taken together, these are the constituents of the phenomenon of "trans-natal sensory continuity" where the embedded sensory capabilities are considered to have been "learnt" and, when accessed subsequently, they are said to have been "remembered". An alternative explanation of trans-natal sensory continuity is provided here in order to focus on the mechanisms of "embedding" and "accessing" instead of the potentially more subjectively conceived outcomes of "learning" and "memory". Thus, the mechanistic concept of "intrauterine sensory entrainment" has been introduced, its foundation being the well-established neuroplastic capability of nervous systems to respond to sensory inputs by reorganising their neural structures, functions, and connections. Five conditions need to be met before "trans-natal sensory continuity" can occur. They are (1) sufficient neurological maturity to support minimal functional activity in specific sensory receptor systems in utero; (2) the presence of sensory stimuli that activate their aligned receptors before birth; (3) the neurological capability for entrained functions within specific sensory modalities to be retained beyond birth; (4) specific sensory stimuli that are effective both before and after birth; and (5) a capability to detect those stimuli when or if they are presented after birth in ways that differ (e.g., in air) from their presentation via fluid media before birth. Numerous beneficial outcomes of this process have been reported for mammalian newborns, but the range of benefits depends on how many of the full set of sensory modalities are functional at the time of birth. Thus, the breadth of sensory capabilities may be extensive, somewhat restricted, or minimal in offspring that are, respectively, neurologically mature, moderately immature, or exceptionally immature at birth. It is noted that birth marks a transition from intrauterine sensory entrainment to extrauterine sensory entrainment in all mammalian young. Depending on their neurological maturity, extrauterine entrainment contributes to the continuing maturation of the different sensory systems that are operational at birth, the later development and maturation of the systems that are absent at birth, and the combined impact of those factors on the behaviour of newborn and young mammals. Intrauterine sensory entrainment helps to prepare mammalian young for life immediately after birth, and extrauterine sensory entrainment continues this process until all sensory modalities develop full functionality. It is apparent that, overall, extrauterine sensory entrainment and its aligned neuroplastic responses underlie numerous postnatal learning and memory events which contribute to the maturation of all sensory capabilities that eventually enable mammalian young to live autonomously.

The Human Nature of Music

Music is at the centre of what it means to be human - it is the sounds of human bodies and minds moving in creative, story-making ways. We argue that music comes from the way in which knowing bodies (Merleau-Ponty) prospectively explore the environment using habitual 'patterns of action,' which we have identified as our innate 'communicative musicality.' To support our argument, we present short case studies of infant interactions using micro analyses of video and audio recordings to show the timings and shapes of intersubjective vocalizations and body movements of adult and child while they improvise shared narratives of meaning. Following a survey of the history of discoveries of infant abilities, we propose that the gestural narrative structures of voice and body seen as infants communicate with loving caregivers are the building blocks of what become particular cultural instances of the art of music, and of dance, theatre and other temporal arts. Children enter into a musical culture where their innate communicative musicality can be encouraged and strengthened through sensitive, respectful, playful, culturally informed teaching in companionship. The central importance of our abilities for music as part of what sustains our well-being is supported by evidence that communicative musicality strengthens emotions of social resilience to aid recovery from mental stress and illness. Drawing on the experience of the first author as a counsellor, we argue that the strength of one person's communicative musicality can support the vitality of another's through the application of skilful techniques that encourage an intimate, supportive, therapeutic, spirited companionship. Turning to brain science, we focus on hemispheric differences and the affective neuroscience of Jaak Panksepp. We emphasize that the psychobiological purpose of our innate musicality grows from the integrated rhythms of energy in the brain for prospective, sensation-seeking affective guidance of vitality of movement. We conclude with a Coda that recalls the philosophy of the Scottish Enlightenment, which built on the work of Heraclitus and Spinoza. This view places the shared experience of sensations of living - our communicative musicality - as inspiration for rules of logic formulated in symbols of language.

Audition-specific temporal processing deficits associated with language function in children with autism spectrum disorder

Sensory processing alterations are highly prevalent in autism spectrum disorder (ASD). Neurobiologically-based theories of ASD propose that abnormalities in the processing of temporal aspects of sensory input could underlie core symptoms of ASD. For example, rapid auditory temporal processing is critical for speech perception, and language difficulties are central to the social communication deficits defining the disorder. This study assessed visual and auditory temporal processing abilities and tested their relation to core ASD symptoms. 53 children (26 ASD, 27 TD) completed visual and auditory psychophysical gap detection tasks to measure gap detection thresholds (i.e., the minimum interval between sequential stimuli needed for individuals to perceive an interruption between the stimuli) in each domain. Children were also administered standardized language assessments such that the relation between individual differences in auditory gap detection thresholds and degree of language and communication difficulties among children with ASD could be assessed. Children with ASD had substantially higher auditory gap detection thresholds compared to children with TD, and auditory gap detection thresholds were correlated significantly with several measures of language processing in this population. No group differences were observed in the visual temporal processing. Results indicate a domain-specific impairment in rapid auditory temporal processing in ASD that is associated with greater difficulties in language processing. Findings provide qualified support for temporal processing theories of ASD and highlight the need for future research testing the nature, extent, and universality of auditory temporal processing deficits in this population. Autism Res 2017, 10: 1845-1856. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

Sensory symptoms are common in ASD. Temporal processing alterations are often implicated, but understudied. The ability to process rapid sensory information, particularly auditory input, is critical for language functioning. This study tested auditory and visual temporal processing in ASD and controls. Findings suggest that rapid auditory (but not visual) processing is impaired in ASD and related to language functioning. These results could provide mechanistic clues to understanding core symptoms and lead to novel intervention targets.

The specificity of the neural response to speech at birth

In this work we ask whether at birth, the human brain responds uniquely to speech, or if similar activation also occurs to a non-speech surrogate 'language'. We compare neural activation in newborn infants to the language heard in utero (English), to an unfamiliar language (Spanish), and to a whistled surrogate language (Silbo Gomero) that, while used by humans to communicate, is not speech. Anterior temporal areas of the neonate cortex are activated in response to both familiar and unfamiliar spoken language, but these classic language areas are not activated to the whistled surrogate form. These results suggest that at the time human infants emerge from the womb, the neural preparation for language is specialized to speech.

STUDIES IN FETAL BEHAVIOR: REVISITED, RENEWED, AND REIMAGINED

Among the earliest volumes of this monograph series was a report by Lester Sontag and colleagues, of the esteemed Fels Institute, on the heart rate of the human fetus as an expression of the developing nervous system. Here, some 75 years later, we commemorate this work and provide historical and contemporary context on knowledge regarding fetal development, as well as results from our own research. These are based on synchronized monitoring of maternal and fetal parameters assessed between 24 and 36 weeks gestation on 740 maternal-fetal pairs compiled from eight separate longitudinal studies, which commenced in the early 1990s. Data include maternal heart rate, respiratory sinus arrhythmia, and electrodrmal activity and fetal heartrate, motor activity, and their integration. Hierarchical linear modeling of developmental trajectories reveals that the fetus develops in predictable ways consistent with advancing parasympathetic regulation. Findings also include:within-fetus stability (i.e., preservation of rank ordering over time) for heart rate, motor, and coupling measures; a transitional period of decelerating development near 30 weeks gestation; sex differences in fetal heart rate measures but not in most fetal motor activity measures; modest correspondence in fetal neurodevelopment among siblings as compared to unrelated fetuses; and deviations from normative fetal development in fetuses affected by intrauterine growth restriction and other conditions. Maternal parameters also change during this period of gestation and there is evidence that fetal sex and individual variation in fetal neurobehavior influence maternal physio-logical processes and the local intrauterine context. Results are discussed within the framework of neuromaturation, the emergence of individual differences, and the bidirectional nature of the maternal-fetal relationship.We pose a number of open questions for future research. Although the human fetus remains just out of reach, new technologies portend an era of accelerated discovery of the earliest period of development

Lifetime development of behavioural phenotype in the house mouse (Mus musculus)

With each trajectory taken during the ontogeny of an individual, the number of optional behavioural phenotypes that can be expressed across its life span is reduced. The initial range of phenotypic plasticity is largely determined by the genetic material/composition of the gametes whereas interacting with the given environment shapes individuals to adapt to/cope with specific demands. In mammalian species, the phenotype is shaped as the foetus grows, depending on the environment in the uterus, which in turn depends on the outer environment the mother experiences during pregnancy. After birth, a complex interaction between innate constitution and environmental conditions shapes individual lifetime trajectories, bringing about a wide range of diversity among individual subjects.

In laboratory mice inbreeding has been systematically induced in order to reduce the genetic variability between experimental subjects. In addition, within most laboratories conducting behavioural phenotyping with mice, breeding and housing conditions are highly standardised. Despite such standardisation efforts a considerable amount of variability persists in the behaviour of mice. There is good evidence that phenotypic variation is not merely random but might involve individual specific behavioural patterns consistent over time. In order to understand the mechanisms and the possible adaptive value of the maintenance of individuality we review the emergence of behavioural phenotypes over the course of the life of (laboratory) mice. We present a literature review summarizing developmental stages of behavioural development of mice along with three illustrative case studies. We conclude that the accumulation of environmental differences and experiences lead to a “mouse individuality” that becomes increasingly stable over the lifetime.

Fetal response to live and recorded maternal speech

The purpose of this study was to compare the fetal response to live and recorded maternal speech following a lengthy history of exposure to a passage spoken by the mother. Participants comprised a convenience sample of 21 pregnant women. The women recited an assigned passage (nursery rhyme) twice daily from 28 to 34 weeks' gestational age (GA), and their fetuses were tested at 34 weeks' GA. During testing, fetal heart rate and movement were measured in response to two different formats of the assigned passage: maternal live voicing and a recording of the mother speaking the passage. The fetal cardiac response varied depending upon the format; however, fetal movement did not. A minimal cardiac deceleration occurred in response to live voicing compared to a cardiac acceleration in response to the recorded format. This is the first study to show differences in the fetal cardiac response to a passage spoken live compared to a recording of the passage following a lengthy history of controlled fetal exposure to the multimodal characteristics of maternal speech. Given the differential response to a live voicing compared to a recorded format, future study that incorporates lengthier exposure to the multimodal characteristics of maternal speech may be warranted.

Emergence and retention of learning in early fetal development

Prior research has demonstrated that the late-term fetus is capable of learning and then remembering a passage of speech for several days, but there are no data to describe the earliest emergence of learning a passage of speech, and thus, how long that learning could be remembered before birth. This study investigated these questions. Pregnant women began reciting or speaking a passage out loud (either Rhyme A or Rhyme B) when their fetuses were 28 weeks gestational age (GA) and continued to do so until their fetuses reached 34 weeks of age, at which time the recitations stopped. Fetuses' learning and memory of their rhyme were assessed at 28, 32, 33, 34, 36 and 38 weeks. The criterion for learning and memory was the occurrence of a stimulus-elicited heart rate deceleration following onset of a recording of the passage spoken by a female stranger. Detection of a sustained heart rate deceleration began to emerge by 34 weeks GA and was statistically evident at 38 weeks GA. Thus, fetuses begin to show evidence of learning by 34 weeks GA and, without any further exposure to it, are capable of remembering until just prior to birth. Further study using dose-response curves is needed in order to more fully understand how ongoing experience, in the context of ongoing development in the last trimester of pregnancy, affects learning and memory.

Physiological reactivity of pregnant women to evoked fetal startle

OBJECTIVE

The bidirectional nature of mother-child interaction is widely acknowledged during infancy and childhood. Prevailing models during pregnancy focus on unidirectional influences exerted by the pregnant woman on the developing fetus. Prior work has indicated that the fetus also affects the pregnant woman. Our objective was to determine whether a maternal psychophysiological response to stimulation of the fetus could be isolated.

METHODS

Using a longitudinal design, an airborne auditory stimulus was used to elicit a fetal heart rate and motor response at 24 (n=47) and 36 weeks (n=45) of gestation. Women were blind to condition (stimulus versus sham). Maternal parameters included cardiac (heart rate) and electrodermal (skin conductance) responses. Multilevel modeling of repeated measures with 5 data points per second was used to examine fetal and maternal responses.

RESULTS

As expected, compared to a sham condition, the stimulus generated a fetal motor response at both gestational ages, consistent with a mild fetal startle. Fetal stimulation was associated with significant, transient slowing of maternal heart rate coupled with increased skin conductance within 10s of the stimulus at both gestational ages. Nulliparous women showed greater electrodermal responsiveness. The magnitude of the fetal motor response significantly corresponded to the maternal skin conductance response at 5, 10, 15, and 30s following stimulation.

CONCLUSION

Elicited fetal movement exerts an independent influence on the maternal autonomic nervous system. This finding contributes to current models of the dyadic relationship during pregnancy between fetus and pregnant woman.

Linking prenatal experience to the emerging musical mind

The musical brain is built over time through experience with a multitude of sounds in the auditory environment. However, learning the melodies, timbres, and rhythms unique to the music and language of one’s culture begins already within the mother’s womb during the third trimester of human development. We review evidence that the intrauterine auditory environment plays a key role in shaping later auditory development and musical preferences. We describe evidence that externally and internally generated sounds influence the developing fetus, and argue that such prenatal auditory experience may set the trajectory for the development of the musical mind.

[Fetal audition. Myth or reality]

Fetal sensory abilities have been considered for a long time as a philosophical question. The aim of this review is to investigate the scientifically proven knowledge about fetal audition. Fetal audition seems to depend on gestational age and sound characteristics. The onset of human fetal hearing is observed at about 26-28 weeks gestational age. Noises from the placenta, the maternal organs and the maternal voice play a major role as current in utero auditory stimuli. Many studies demonstrate that the fetus forms memories of his hearing experiences allowing some authors to use the term "fetal learning". The fetus can memorize not only his mother's voice but also more complex acoustic external sounds with a big ability of discrimination. Moreover, most studies strengthen the hypothesis of an implicit musical ability of the human brain.