Acute relaxation during pregnancy leads to a reduction in maternal electrodermal activity and self-reported stress levels.

BACKGROUND: Prenatal maternal stress can have adverse effects on birth outcomes and fetal development. Relaxation techniques have been examined as potential countermeasures. This study investigates different relaxation techniques and their effect on self-reported stress levels and physiological stress levels in pregnant women. METHODS: In this cross-sectional study, 38 pregnant women in their 30th to 40th gestational week were assigned to one of three, 20-min lasting relaxation groups: listening to music (N = 12), following a guided imagery (N = 12) or resting (N = 12). The intervention, i.e., acute relaxation (music, guided imagery or resting) took place once for each study participant. Study inclusion criteria were age over 18 years, German speaking, singleton and uncomplicated pregnancy during the 30th and 40th week of gestation. The stress levels were determined during the study. Current stress level during the study was assessed by a visual analogue scale. Chronic stress levels were assessed by the Trier Inventory of Chronic Stress and the Pregnancy Distress questionnaire. Multivariate analyses of covariance were performed and dependent measures included stress levels as well as physiological measures, i.e., cardiovascular activity (electrocardiogram) and skin conductance levels. RESULTS: All three forms of relaxation led to reduced maternal stress which manifested itself in significantly decreased skin conductance, F(3,94) = 18.011, p = .001, ηp2 = .365, and subjective stress levels after the interventions with no significant group difference. Post-intervention stress ratings were further affected by gestational age, with less subjective relaxation in women later in gestation, F (1, 34)=4.971, p = .032, ηp2 = .128. CONCLUSION: Independent of relaxation technique, single, 20-min relaxation intervention (music, guided imagery or resting) can significantly reduce maternal stress. Notably, women at an earlier stage in their pregnancy reported higher relaxation after the intervention than women later in gestation. Hence, gestational age may influence perceived stress levels and should be considered when evaluating relaxation or stress management interventions during pregnancy. TRIAL REGISTRATION: Not applicable.

Dynamics of nonlinguistic statistical learning: From neural entrainment to the emergence of explicit knowledge.

Humans are highly attuned to patterns in the environment. This ability to detect environmental patterns, referred to as statistical learning, plays a key role in many diverse aspects of cognition. However, the spatiotemporal neural mechanisms underlying implicit statistical learning, and how these mechanisms may relate or give rise to explicit learning, remain poorly understood. In the present study, we investigated these different aspects of statistical learning by using an auditory nonlinguistic statistical learning paradigm combined with magnetoencephalography. Twenty-four healthy volunteers were exposed to structured and random tone sequences, and statistical learning was quantified by neural entrainment. Already early during exposure, participants showed strong entrainment to the embedded tone patterns. A significant increase in entrainment over exposure was detected only in the structured condition, reflecting the trajectory of learning. While source reconstruction revealed a wide range of brain areas involved in this process, entrainment in areas around the left pre-central gyrus as well as right temporo-frontal areas significantly predicted behavioral performance. Sensor level results confirmed this relationship between neural entrainment and subsequent explicit knowledge. These results give insights into the dynamic relation between neural entrainment and explicit learning of triplet structures, suggesting that these two aspects are systematically related yet dissociable. Neural entrainment reflects robust, implicit learning of underlying patterns, whereas the emergence of explicit knowledge, likely built on the implicit encoding of structure, varies across individuals and may depend on factors such as sufficient exposure time and attention.

Automated Detection of Fetal Brain Signals with Principal Component Analysis.

Detection of fetal brain signals in fetal magnetoencephalographic recordings is - due to the low signal to noise ratio - challenging for researchers in this field. Up to now, state of the art is a manual evaluation of the signal. To make the evaluation more reproducible and less time consuming, an approach using Principal Component Analysis is introduced. Locations of the channels of most importance for the first three principal components are taken into account and their possibility of resembling brain activity evaluated. Data with auditory stimulation are taken for this analysis and trigger averaged signals from the channels selected as brain activity (manually & automatically) compared. Comparisons are done with regard to their average baseline activity, activity during a window of interest and timing and amplitude of their highest auditory event-related peak. The number of evaluable data sets showed to be lower for the automated compared to manual approach but auditory event-related peaks did not differ significantly in amplitude or timing and in both cases there was a significant activity change following the tone event. The given results and the advantage of reproducibility make this method a valid alternative.

Neuromagnetic signatures of syllable processing in fetuses and infants provide no evidence for habituation.

BACKGROUND: Habituation, as a basic form of learning, is characterized by decreasing amplitudes of neuronal reaction following repeated stimuli. Recent studies indicate that habituation to pure tones of different frequencies occurs in fetuses and infants. AIMS: Neural processing of different syllables in fetuses and infants was investigated. STUDY DESIGN: An auditory habituation paradigm including two different sequences of syllables was presented to each subject. Each sequence consisted of eight syllables (sequence /ba/: 5× /ba/, 1× /bi/ (dishabituator), 2× /ba/; sequence /bi/: 5× /bi/, 1× /ba/ (dishabituator), 2× /bi/). Each subject was stimulated with 140 sequences. Neuromagnetic signatures of auditory-evoked responses (AER) were recorded by fetal magnetoencephalography (fMEG). SUBJECTS: Magnetic brain signals of N=30 fetuses (age: 28-39weeks of gestation) and N=28 infants (age: 0-3months) were recorded. Forty-two of the 60 fetal recordings and 29 of the 58 infant recordings were included in the final analysis. OUTCOME MEASURES: AERs were recorded and amplitudes were normalized to the amplitude of the first stimulus. RESULTS: In both fetuses and infants, the amplitudes of AERs were found not to decrease with repeated stimulation. In infants, however, amplitude of syllable 6 (dishabituator) was significantly increased compared to syllable 5 (p=0.026). CONCLUSIONS: Fetuses and infants showed AERs to syllables. Unlike fetuses, infants showed a discriminative neural response to syllables. Habituation was not observed in either fetuses or infants. These findings could be important for the investigation of early cognitive competencies and may help to gain a better understanding of language acquisition during child development.

Magnetoencephalographic signatures of numerosity discrimination in fetuses and neonates.

Numerosity discrimination has been demonstrated in newborns, but not in fetuses. Fetal magnetoencephalography allows non-invasive investigation of neural responses in neonates and fetuses. During an oddball paradigm with auditory sequences differing in numerosity, evoked responses were recorded and mismatch responses were quantified as an indicator for auditory discrimination. Thirty pregnant women with healthy fetuses (last trimester) and 30 healthy term neonates participated. Fourteen adults were included as a control group. Based on measurements eligible for analysis, all adults, all neonates, and 74% of fetuses showed numerical mismatch responses. Numerosity discrimination appears to exist in the last trimester of pregnancy.

Auditory habituation in the fetus and neonate: an fMEG study.

Habituation--the most basic form of learning--is used to evaluate central nervous system (CNS) maturation and to detect abnormalities in fetal brain development. In the current study, habituation, stimulus specificity and dishabituation of auditory evoked responses were measured in fetuses and newborns using fetal magnetoencephalography (fMEG). An auditory habituation paradigm consisting of 100 trains of five 500 Hz tones, one 750 Hz tone (dishabituator) and two more 500 Hz tones, respectively, were presented to 41 fetuses (gestational age 30-39 weeks) and 22 newborns or babies (age 6-89 days). A response decrement between the first and fifth tones (habituation), an increment between the fifth tone and the dishabituator (stimulus specificity) and an increment between the fifth (last tone before the dishabituator) and seventh tones (first tone after the dishabituator) (dishabituation) were expected. Fetuses showed weak responses to the first tone. However, a significant response decrement between the second and fifth tones (habituation) and a significant increment between the fifth tone and the dishabituator (stimulus specificity) were found. No significant difference was found for dishabituation nor was a developmental trend found at the group level. From the neonatal data, significant values for stimulus specificity were found. Sensory fatigue or adaptation was ruled out as a reason for the response decrement due to the strong reactions to the dishabituator. Taken together, the current study used fMEG to directly show fetal habituation and provides evidence of fetal learning in the last trimester of pregnancy.