Newborns discriminate novel from harmonic sounds: A study using magnetoencephalography

Challenges and new perspectives of developmental cognitive EEG studies

Despite shared procedures with adults, electroencephalography (EEG) in early development presents many specificities that need to be considered for good quality data collection. In this paper, we provide an overview of the most representative early cognitive developmental EEG studies focusing on the specificities of this neuroimaging technique in young participants, such as attrition and artifacts. We also summarize the most representative results in developmental EEG research obtained in the time and time-frequency domains and use more advanced signal processing methods. Finally, we briefly introduce three recent standardized pipelines that will help promote replicability and comparability across experiments and ages. While this paper does not claim to be exhaustive, it aims to give a sufficiently large overview of the challenges and solutions available to conduct robust cognitive developmental EEG studies.

Auditory Processing of the Brain Is Enhanced by Parental Singing for Preterm Infants

As the human auditory system is highly malleable in infancy, perinatal risk factors, such as preterm birth, may affect auditory development. In comparison to healthy full-term infants, preterm infants show abnormal auditory brain responses at term age, which may have long-term detrimental outcomes. To achieve an optimal neonatal care environment for preterm-born infants, many early interventions have been developed. Musical interventions developed for neonatal intensive care units (NICUs) have shown beneficial effects on vital functions and weight gain of preterm infants and might also influence basic auditory processing and thereby enhance outcomes. In the present study, we tested the effect of parental singing during kangaroo care on auditory processing of standardized audio stimuli. Preterm infants (born between 24 and 32 weeks of gestation) were randomized to singing intervention (n = 13) or control (n = 8) groups. The auditory processing was tested using two audio paradigms assessed with magnetoencephalography (MEG) at term corresponding age. To verify that the paradigms elicit responses in MEG, we studied 12 healthy full-term infants. In the singing intervention group, parents were instructed by a music therapist twice a week for 4 weeks to sing or hum during kangaroo care in an infant-directed way. The control group received standard kangaroo care. The results show that the infants in the singing intervention group show larger neural responses than those in the control group when controlling for the total amount of singing during kangaroo care. Our findings suggest that incorporating singing into kangaroo care may be beneficial for preterm infants, but the effect may not be due to exposure to singing but instead positive parenting, improved parental self-esteem and improved caregiver sensitivity.

Early differences in auditory processing relate to Autism Spectrum Disorder traits in infants with Neurofibromatosis Type I

BACKGROUND

Sensory modulation difficulties are common in children with conditions such as Autism Spectrum Disorder (ASD) and could contribute to other social and non-social symptoms. Positing a causal role for sensory processing differences requires observing atypical sensory reactivity prior to the emergence of other symptoms, which can be achieved through prospective studies.

METHODS

In this longitudinal study, we examined auditory repetition suppression and change detection at 5 and 10 months in infants with and without Neurofibromatosis Type 1 (NF1), a condition associated with higher likelihood of developing ASD.

RESULTS

In typically developing infants, suppression to vowel repetition and enhanced responses to vowel/pitch change decreased with age over posterior regions, becoming more frontally specific; age-related change was diminished in the NF1 group. Whilst both groups detected changes in vowel and pitch, the NF1 group were largely slower to show a differentiated neural response. Auditory responses did not relate to later language, but were related to later ASD traits.

CONCLUSIONS

These findings represent the first demonstration of atypical brain responses to sounds in infants with NF1 and suggest they may relate to the likelihood of later ASD.

Neural Correlates of Voice Perception in Newborns and the Influence of Preterm Birth

Maternal voice is a highly relevant stimulus for newborns. Adult voice processing occurs in specific brain regions. Voice-specific brain areas in newborns and the relevance of an early vocal exposure on these networks have not been defined. This study investigates voice perception in newborns and the impact of prematurity on the cerebral processes. Functional magnetic resonance imaging (fMRI) and high-density electroencephalography (EEG) were used to explore the brain responses to maternal and stranger female voices in full-term newborns and preterm infants at term-equivalent age (TEA). fMRI results and the EEG oddball paradigm showed enhanced processing for voices in preterms at TEA than in full-term infants. Preterm infants showed additional cortical regions involved in voice processing in fMRI and a late mismatch response for maternal voice, considered as a first trace of a recognition process based on memory representation. Full-term newborns showed increased cerebral activity to the stranger voice. Results from fMRI, oddball, and standard auditory EEG paradigms highlighted important change detection responses to novelty after birth. These findings suggest that the main components of the adult voice-processing networks emerge early in development. Moreover, an early postnatal exposure to voices in premature infants might enhance their capacity to process voices.

Magnetic Source Imaging and Infant MEG: Current Trends and Technical Advances

Magnetoencephalography (MEG) is known for its temporal precision and good spatial resolution in cognitive brain research. Nonetheless, it is still rarely used in developmental research, and its role in developmental cognitive neuroscience is not adequately addressed. The current review focuses on the source analysis of MEG measurement and its potential to answer critical questions on neural activation origins and patterns underlying infants’ early cognitive experience. The advantages of MEG source localization are discussed in comparison with functional magnetic resonance imaging (fMRI) and functional near-infrared spectroscopy (fNIRS), two leading imaging tools for studying cognition across age. Challenges of the current MEG experimental protocols are highlighted, including measurement and data processing, which could potentially be resolved by developing and improving both software and hardware. A selection of infant MEG research in auditory, speech, vision, motor, sleep, cross-modality, and clinical application is then summarized and discussed with a focus on the source localization analyses. Based on the literature review and the advancements of the infant MEG systems and source analysis software, typical practices of infant MEG data collection and analysis are summarized as the basis for future developmental cognitive research.

No interaction between rivastigmine and citalopram on memory and novelty processing in healthy human volunteers

BACKGROUND

Animal literature suggests an interaction between acetylcholine and serotonin on cognitive functions.

AIMS

The aim of the current study was to assess whether both neurotransmitters interact during memory and novelty processing in humans.

METHODS

We tested the interaction between acetylcholine and serotonin on cognitive functions in healthy volunteers by means of treatment with rivastigmine and citalopram, respectively.

RESULTS

The main result of the study showed that during the verbal learning task participants significantly recalled fewer words after citalopram treatment than after rivastigmine or placebo during both the immediate and delayed recall tasks. Rivastigmine was not able to reverse the impairing effect of citalopram.

CONCLUSIONS

This finding is in line with previous studies in which we manipulated acetylcholine and serotonin in different manners. Taken together, these studies in humans do not support the notion from animal studies that these two neurotransmitters interact on cognitive functions.

Magnetoencephalography and the infant brain

Magnetoencephalography (MEG) is a non-invasive neuroimaging technique that provides whole-head measures of neural activity with millisecond temporal resolution. Over the last three decades, MEG has been used for assessing brain activity, most commonly in adults. MEG has been used less often to examine neural function during early development, in large part due to the fact that infant whole-head MEG systems have only recently been developed. In this review, an overview of infant MEG studies is provided, focusing on the period from birth to three years. The advantages of MEG for measuring neural activity in infants are highlighted (See Box 1), including the ability to assess activity in brain (source) space rather than sensor space, thus allowing direct assessment of neural generator activity. Recent advances in MEG hardware and source analysis are also discussed. As the review indicates, efforts in this area demonstrate that MEG is a promising technology for studying the infant brain. As a noninvasive technology, with emerging hardware providing the necessary sensitivity, an expected deliverable is the capability for longitudinal infant MEG studies evaluating the developmental trajectory (maturation) of neural activity. It is expected that departures from neuro-typical trajectories will offer early detection and prognosis insights in infants and toddlers at-risk for neurodevelopmental disorders, thus paving the way for early targeted interventions.

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

We evaluated the feasibility of a multi-feature mismatch negativity (MMN) paradigm in studying auditory processing of healthy newborns. The aim was to examine the automatic change-detection and processing of semantic and emotional information in speech in newborns. Brain responses of 202 healthy newborns were recorded with a multi-feature paradigm including a Finnish bi-syllabic pseudo-word/ta-ta/as a standard stimulus, six linguistically relevant deviant stimuli and three emotionally relevant stimuli (happy, sad, angry). Clear responses to emotional sounds were found already at the early latency window 100-200 ms, whereas responses to linguistically relevant minor changes and emotional stimuli at the later latency window 300-500 ms did not reach significance. Moreover, significant interaction between gender and emotional stimuli was found in the early latency window. Further studies on using multi-feature paradigms with linguistic and emotional stimuli in newborns are needed, especially those containing of follow-ups, enabling the assessment of the predictive value of early variations between subjects.

Effect of maturation on suprasegmental speech processing in full- and preterm infants: a mismatch negativity study

Infants born prematurely are at higher risk for later linguistic deficits present in delayed or atypical processing of phonetic and prosodic information. In order to be able to specify the nature of this atypical development, it is important to investigate the role of early experience in language perception. According to the concept of Gonzalez-Gomez and Nazzi (2012) there is a special intrauterine sensitivity to the prosodic features of languages that should have a special role in language acquisition. Therefore, we may also assume that pre- and full-term infants having months difference in intrauterine experience show different maturation patterns of processing prosodic and phonetic information present at word level. The aim of our study was to investigate the effect of these differences on word stress pattern vs. phoneme information processing. Two age groups of infants (6 and 10 month-olds) were included in our study. 21 of 46 of the total of infants investigated were prematurely born with low birth weight. We used the mismatch negativity (MMN) event related brain potential (ERP) component, a widely used electrophysiological correlate of acoustic change detection, for testing the assumed developmental changes of phoneme and word stress discrimination. In a passive oddball paradigm we used a word as standard, a pseudo-word as phoneme deviant, and an illegally uttered word as stress deviant. Our results showed no differences in MMN responses in the phoneme deviant condition between the groups, meaning a relatively intact maturation of phoneme processing of preterm infants as compared to their contemporaries. However, the mismatch responses measured in the stress condition revealed significant between-group differences. These results strengthen the view that the total length of intrauterine experience influences the time of emergence of prosodic processing.

Effects of remifentanil on processing of auditory stimuli: a combined MEG/EEG study

Remifentanil (Ultiva(®)) is a potent ultra-short acting mu-opioid receptor agonist used for perioperative pain treatment and anaesthesia. So far, it is not known how sensitive the cognitive processing of auditory perception elicited by the mismatch negativity (MMN) paradigm is to opioids. The present exploratory study investigated how the opioid remifentanil modulates different stages of auditory processing as reflected in the MMN(m) and P3a(m). We recorded electroencephalography (EEG) and magnetoencephalography (MEG) during auditory stimulation under remifentanil or placebo infusion in 20 healthy participants. For the MMN, a gender effect was found for tones deviating in frequency (± 10%) from the standard tone. Remifentanil increased the amplitude of the frequency MMN at F3 in females but not in males. No effect of treatment was found for the MMN(m) or the novel P3a(m). These results suggest that while the bottom-up stimulus change detection system for auditory stimuli appears to be relatively insensitive to opioids, the automatic attention switch caused by the change detection seems to be modulated by the opioid system in females. The multiple deviant paradigm including novel sounds is a promising tool for investigating pharmacological manipulation of different stages of auditory processing. Furthermore, combining the two techniques will yield more specific information about the drug effects on MMN(m).

Context effects on processing widely deviant sounds in newborn infants

Detecting and orienting toward sounds carrying new information is a crucial feature of the human brain that supports adaptation to the environment. Rare, acoustically widely deviant sounds presented amongst frequent tones elicit large event-related brain potentials (ERPs) in neonates. Here we tested whether these discriminative ERP responses reflect only the activation of fresh afferent neuronal populations (i.e., neuronal circuits not affected by the tones) or they also index the processing of contextual mismatch between the rare and the frequent sounds. In two separate experiments, we presented sleeping newborns with 150 different environmental sounds and the same number of white noise bursts. Both sounds served either as deviants in an oddball paradigm with the frequent standard stimulus a tone (Novel/Noise deviant), or as the standard stimulus with the tone as deviant (Novel/Noise standard), or they were delivered alone with the same timing as the deviants in the oddball condition (Novel/Noise alone). Whereas the ERP responses to noise-deviants elicited similar responses as the same sound presented alone, the responses elicited by environmental sounds in the corresponding conditions morphologically differed from each other. Thus whereas the ERP response to the noise sounds can be explained by the different refractory state of stimulus-specific neuronal populations, the ERP response to environmental sounds indicated context-sensitive processing. These results provide evidence for an innate tendency of context-dependent auditory processing as well as a basis for the different developmental trajectories of processing acoustical deviance and contextual novelty.

Separating acoustic deviance from novelty during the first year of life: a review of event-related potential evidence

Orienting to salient events in the environment is a first step in the development of attention in young infants. Electrophysiological studies have indicated that in newborns and young infants, sounds with widely distributed spectral energy, such as noise and various environmental sounds, as well as sounds widely deviating from their context elicit an event-related potential (ERP) similar to the adult P3a response. We discuss how the maturation of event-related potentials parallels the process of the development of passive auditory attention during the first year of life. Behavioral studies have indicated that the neonatal orientation to high-energy stimuli gradually changes to attending to genuine novelty and other significant events by approximately 9 months of age. In accordance with these changes, in newborns, the ERP response to large acoustic deviance is dramatically larger than that to small and moderate deviations. This ERP difference, however, rapidly decreases within first months of life and the differentiation of the ERP response to genuine novelty from that to spectrally rich but repeatedly presented sounds commences during the same period. The relative decrease of the response amplitudes elicited by high-energy stimuli may reflect development of an inhibitory brain network suppressing the processing of uninformative stimuli. Based on data obtained from healthy full-term and pre-term infants as well as from infants at risk for various developmental problems, we suggest that the electrophysiological indices of the processing of acoustic and contextual deviance may be indicative of the functioning of auditory attention, a crucial prerequisite of learning and language development.

Electrophysiological analysis of the role of novelty in the von Restorff effect

Items that are distinctive with respect to their context tend to be recalled better than nondistinctive items, a finding known as the von Restorff effect. The goal of this study was to elucidate the role of novelty in this effect. In two experiments, participants performed a dual task in which they had to study words presented visually while to-be ignored sounds were played over earphones. Sounds could be either standard or novel, and words could be presented in standard or novel font. Sounds were presented either simultaneously with the words (Experiment 1) or preceding them (Experiment 2). Electrophysiological correlates of novelty processing, the N2b and P3a ERP components, were recorded while the words were studied. It was seen that cued recall was better for words presented in novel fonts than for words in a standard font (the von Restorff effect). Words presented while novel sounds were played were remembered worse (Experiment 1) or equally well (Experiment 2) than those combined with standard sounds. Words presented in novel fonts elicited enhanced N2b, P3a, P3b, and N400 components; however, none of these components were specifically larger for subsequently recalled novel-font words. A larger N2b was found for recalled than for nonrecalled words, but this effect was not specific for words presented in novel font. We hypothesized that if novelty was beneficial for memory processing, the N2-P3 complex would be more enhanced for novel words that were later recalled than for those not recalled. The data showed otherwise. This suggests that novelty processing, as indexed by the N2-P3 novelty components, is not the main cause of the von Restorff effect.

Validity in assessing time processing ability, test equating of KaTid-Child and KaTid-Youth

BACKGROUND

There is a need for instruments with acceptable psychometric properties for measuring time management/time processing ability. KaTid-Child (Swedish: Kit for assessing Time processing ability) was developed for children aged 5-10 years. To meet needs of assessing older children, KaTid-Youth was created. The aim of this study was to investigate the validity of KaTid-Youth.

METHODS

  This study investigates the validity of KaTid-Youth using Rasch models: partial credit and common item equating.

RESULTS

Results indicate that KaTid-Youth has acceptable psychometric properties and seems to measure the same construct as KaTid-Child.

CONCLUSIONS

Indications of gender differences in the sample call for further research. The results indicate that time processing ability can be seen as one construct in which time perception, orientation and management can be operationalized as different levels of complexity in time processing ability. Expressions of time processing ability differ at different ages. Thus, early intervention in time perception and time orientation may be needed to promote time management in later childhood. Professionals need to take time processing ability into consideration when meeting children who risk delayed development of daily time management.

Magnetoencephalography in neonatology

Magnetoencephalography (MEG) is a noninvasive method to study brain activity. In the previous decade the advantages of MEG -- good temporal resolution combined with good spatial resolution allowing separation of activated brain areas -- have been successfully used in gaining new information about the neonatal brain functioning. In this review, we discuss the findings from studies of spontaneous magnetoencephalogram and evoked responses to somatosensory, auditory, and visual stimulation. Our group has shown that stimulation of the upper limb in neonates evokes a response sequence reflecting activation of both primary (S(I)) and secondary somatosensory (S(II)) cortices. Like in mature brains, the earliest cortical response to median nerve stimulation reflects the arrival of afferent information to S(I). However, source modeling of the subsequent activation from S(I)suggests immature cortical functioning in neonates. Another feature typical for neonates is that the S(II)response is prominent in quiet sleep, unlike in adults in whom it diminishes in sleep. Interestingly, in very prematurely-born infants, we found alterations of the somatosensory responses at both group and individual levels. MEG provides a novel way to look at brain activity in neonates and can be used to increase knowledge of the development of brain processing and its disturbances.

Auditory processing during sleep in preterm infants: An event related potential study

Auditory processing during sleep was investigated in premature infants by auditory event related potentials (AERPs). Twenty-six premature infants (mean GA 30 week- range 25-35) admitted to a neonatal intensive care unit were studied, prior to discharge, in active and quiet sleep at a mean post-conceptional age of 35 weeks. Infant state was determined by behavioral observation according to standard criteria. An auditory odd-ball paradigm was used with frequently occurring 'standard' tones at 1000Hz and infrequent 'deviant' tones at 2000Hz. Waveforms were recorded at Fz, Cz, Pz, T3 and T4 scalp locations. Measurements were performed in 18 patients because 8 preterm infants were excluded since they had less than the required artifact-free deviant trials in each sleep state. The responses to standard tones were equally recorded in both active and quiet sleep, but auditory responses to deviant tones consisting of an increased frontal negativity in the time period from 200 to 300ms after the stimulus were recorded only in active sleep. A significant effect of electrode placement, for frontal location by sleep condition and sleep condition by 50ms time windows was shown by repeated measures analyses of variance. The significance of these findings on evoked potential methodology in preterm infants admitted to neonatal intensive care unit is discussed.

Increasing the efficiency of neonatal MEG measurements by alternating auditory and tactile stimulation

OBJECTIVE

To evaluate the possible effect of intervening auditory stimulation on somatosensory evoked magnetic fields in newborns.

METHODS

We recorded auditory and tactile evoked responses with magnetoencephalography (MEG) from two groups of healthy newborns. One group (n=11) received only tactile stimuli to the index finger, the other (n=11) received alternating tactile and auditory (vowel [a:] with 300-ms duration) stimuli. The interval between subsequent tactile stimuli was always 2 s. We analyzed the equivalent current dipoles (ECDs) of the main auditory and somatosensory responses.

RESULTS

The ECDs of the tactile responses agreed with activation of the primary somatosensory cortex at ∼60 ms and the secondary somatosensory region at ∼200 ms. The source of the auditory response (∼250 ms) was clearly distinct from those to tactile stimulation and in line with auditory cortex activation. The intervening auditory stimulation did not affect the strength, latency, or location of the ECDs of the tactile responses.

CONCLUSIONS

Auditory and tactile MEG responses from newborns can be obtained in one measurement session.

SIGNIFICANCE

The alternating stimulation can be used to shorten the total measurement time and/or to improve the signal to noise ratio by collecting more data.

Categories of Novelty and States of Uncertainty

The concept of novelty has acquired a large number of diverse referents over the past quarter-century as a result of new methods that permit measurement of a variety of biological and behavioral reactions to novel incentives in both humans and animals. As a result, the term has acquired varied meanings. This analysis of novelty makes four claims. First, the specific state of uncertainty that a novel event creates depends on its origin. Second, unexpected events that alter the immediate stimulus surround (called stimulus novelty) should be distinguished from those that are inconsistent with an agent's long term knowledge (called conceptual novelty). Third, the critical features that render an event novel can vary with the agent's intention to classify or to act on an object and the balance between these two frames changes with development. Finally, the state of uncertainty created when an agent must choose one response from two or more alternatives differs from the states provoked by stimulus and conceptual novelty.

Change detection in newborns using a multiple deviant paradigm: a study using magnetoencephalography

OBJECTIVE

Mismatch responses are elicited to changes in sound streams in healthy newborns. In the ideal case, these responses can predict cognitive problems later in life. We employed a multiple deviant paradigm for a fast assessment of the ability of the newborn brain to respond to various types of acoustic changes.

METHODS

In 12 healthy newborns, we recorded an electroencephalogram (EEG) and magnetoencephalogram while presenting auditory stimuli. Between repeated stimuli, four types of acoustic changes (frequency, intensity, duration, and a gap) were presented, varying in deviance magnitude.

RESULTS

One major response was present in the neonatal evoked potentials and fields at 250-260 ms. Magnetic mismatch responses were elicited to all change types except for the duration deviant and they were positive in polarity. The frequency deviant elicited more positive EEG amplitudes than the standard, whereas the response to the duration deviant was more negative.

CONCLUSIONS

These results show that newborns can detect changes to at least four types of deviances within a sound stream. Furthermore, the use of magneto- and electroencephalography is complementary in newborns, since the methods may reveal different outcomes.

SIGNIFICANCE

Further studies are warranted to determine whether the present study design can play a role in testing auditory function in clinical infant populations.

Timbre-independent extraction of pitch in newborn infants

The ability to separate pitch from other spectral sound features, such as timbre, is an important prerequisite of veridical auditory perception underlying speech acquisition and music cognition. The current study investigated whether or not newborn infants generalize pitch across different timbres. Perceived resonator size is an aspect of timbre that informs the listener about the size of the sound source, a cue that may be important already at birth. Therefore, detection of infrequent pitch changes was tested by recording event-related brain potentials in healthy newborn infants to frequent standard and infrequent pitch-deviant sounds while the perceived resonator size of all sounds was randomly varied. The elicitation of an early negative and a later positive discriminative response by deviant sounds demonstrated that the neonate auditory system represents pitch separately from timbre, thus showing advanced pitch processing capabilities.

Sleeping newborns extract prosody from continuous speech

OBJECTIVE

Behavioral experiments show that infants use both prosodic and statistical cues in acquiring language. However, it is not yet clear whether these prosodic and statistical tools are already present at birth.

METHODS

We recorded brain responses of sleeping newborns to natural sounds rich in prosody, namely singing and continuous speech, and to two impoverished manipulations of speech. A total of 11 newborns were presented with continuous speech, singing, and degraded speech, while MEG was recorded.

RESULTS

We found that a brain response elicited to the prosodically rich singing and continuous natural speech conditions decreased dramatically when the prosody in the speech was impoverished.

CONCLUSIONS

We claim that this response is the indicator of the infants' sensitivity to prosodic cues in language, which is already present at birth during natural sleep.

SIGNIFICANCE

The indicators of detection of prosody may be crucial in assessing the normal and abnormal cortical function in newborns, especially of those infants at-risk for language problems.

The mismatch negativity (MMN) in basic research of central auditory processing: a review

In the present article, the basic research using the mismatch negativity (MMN) and analogous results obtained by using the magnetoencephalography (MEG) and other brain-imaging technologies is reviewed. This response is elicited by any discriminable change in auditory stimulation but recent studies extended the notion of the MMN even to higher-order cognitive processes such as those involving grammar and semantic meaning. Moreover, MMN data also show the presence of automatic intelligent processes such as stimulus anticipation at the level of auditory cortex. In addition, the MMN enables one to establish the brain processes underlying the initiation of attention switch to, conscious perception of, sound change in an unattended stimulus stream.

Neonatal frequency discrimination in 250–4000-Hz range: Electrophysiological evidence

OBJECTIVE

The precision of sound frequency discrimination in newborn infants in the 250-4000-Hz frequency range was determined using the neonatal electrophysiological mismatch response (MMR), the infant equivalent of adult mismatch negativity (MMN).

METHODS

The electroencephalogram (EEG) was recorded in 11 full-term sleeping newborn infants mostly in active sleep (67% of the time). Pure tones were presented through loudspeakers in an oddball paradigm with a 800-ms stimulus onset asynchrony (SOA). Each stimulus block contained a standard (p=0.76) of 250, 1000, or 4000Hz in frequency (in separate blocks) and deviants with a frequency change of either 5% or 20% of the standard (p=0.12 of each).

RESULTS

A positive ERP deflection was found at 200-300ms from stimulus onset in response to the 20% deviation from the 250, 1000, and 4000Hz standard frequencies. The amplitude of the response in the 200-300ms time window was significantly larger for the 20% than 5% deviation.

CONCLUSIONS

We observed in newborn infants automatic frequency discrimination as reflected by a positive MMR. The newborns were able to discriminate frequency change of 20% in the 250-4000-Hz frequency range, whereas the discrimination of the 5% frequency change was not statistically confirmed.

SIGNIFICANCE

The present data hence suggest that the neonatal frequency discrimination has lower resolution than that in adult and older children data.

Magnetoencephalography of the newborn brain

This paper reviews the use of event-related magnetic fields (ERFs) in infants; ERFs can be derived from magnetoencephalography by means of averaging. Basic perceptive skills are important prerequisites for the infant's later development. The automatic cortical processes related to processing auditory, somatosensory and visual stimuli can be addressed by using responses recorded directly from the brain. The traditional method, the event-related potential (ERP), has recently been accompanied by ERFs. Similarly to ERPs, higher processes related to short-term memory, stimulus comparisons, and attention allocation can also be studied with ERFs. Further, since addressing the neonatal higher cognitive and social capabilities is challenging using only behavioural means, ERFs provide information on these important functions at a very early stage immediately after birth or in some cases even before birth. The main advantage of ERFs, compared to ERPs, is detection of the signals with high accuracy both with respect to the noise level and estimation of the spatial location.