Imaging affective and non-affective touch processing in two-year-old children

Touch is an important component of early parent-child interaction and plays a critical role in the socio-emotional development of children. However, there are limited studies on touch processing amongst children in the age range from one to three years. The present study used frequency-domain diffuse optical tomography (DOT) to investigate the processing of affective and non-affective touch over left frontotemporal brain areas contralateral to the stimulated forearm in two-year-old children. Affective touch was administered by a single stroke with a soft brush over the child's right dorsal forearm at 3 cm/s, while non-affective touch was provided by multiple brush strokes at 30 cm/s. We found that in the insula, the total haemoglobin (HbT) response to slow brushing was significantly greater than the response to fast brushing (slow > fast). Additionally, a region in the postcentral gyrus, Rolandic operculum and superior temporal gyrus exhibited greater response to fast brushing than slow brushing (fast > slow). These findings confirm that an adult-like pattern of haemodynamic responses to affective and non-affective touch can be recorded in two-year-old subjects using DOT. To improve the accuracy of modelling light transport in the two-year-old subjects, we used a published age-appropriate atlas and deformed it to match the exterior shape of each subject's head. We estimated the combined scalp and skull, and grey matter (GM) optical properties by fitting simulated data to calibrated and coupling error corrected phase and amplitude measurements. By utilizing a two-compartment cerebrospinal fluid (CSF) model, the accuracy of estimation of GM optical properties and the localization of activation in the insula was improved. The techniques presented in this paper can be used to study neural development of children at different ages and illustrate that the technology is well-tolerated by most two-year-old children and not excessively sensitive to subject movement. The study points the way towards exciting possibilities in functional imaging of deeper functional areas near sulci in small children.Peer reviewe

Magnetic-Stimulation-Related Physiological Artifacts in Hemodynamic Near-Infrared Spectroscopy Signals

Peer reviewe

Relationship between maternal pregnancy-related anxiety and infant brain responses to emotional speech – a pilot study

Background: Maternal pregnancy-related anxiety (PRA) is reportedly related to neurodevelopmental outcomes of infants. However, the relationship between maternal PRA and the processing of emotions in the infant brain has not been extensively studied with neuroimaging. The objective of the present pilot study is to investigate the relationship between maternal PRA and infant hemodynamic responses to emotional speech at two months of age. Methods: The study sample included 19 mother-infant dyads from a general sample of a population of Caucasian mothers. Self-reported Pregnancy-Related Anxiety Questionnaire (PRAQ-R2) data was collected from mothers during pregnancy at gestational weeks (gwks) 24 (N = 19) and 34 (N = 18). When their infants were two months old, the infants' brains functional responses to emotional speech in the left fronto-temporoparietal cortex were recorded using diffuse optical tomography (DOT). Results: Maternal PRAQ-R2 scores at gwk 24 correlated negatively with the total hemoglobin (HbT) responses to sad speech on both sides of the temporoparietal junction (Spearman's rank correlation coefficient rho = -0.87). The correlation was significantly greater at gwk 24 than gwk 34 (rho = -0.42). Limitations: The field of view of the measurement did not include the right hemisphere or parts of the frontal cortex. The sample size is moderate and the mothers were relatively highly educated, thus there may be some differences between the study sample and the general population. Conclusions: Maternal pregnancy-related anxiety may affect child brain emotion processing development. Further research is needed to understand the functional and developmental significance of the findings.Peer reviewe

Imaging affective and non-affective touch processing in two-year-old children

Touch is an important component of early parent-child interaction and plays a critical role in the socio-emotional development of children. However, there are limited studies on touch processing amongst children in the age range from one to three years. The present study used frequency-domain diffuse optical tomography (DOT) to investigate the processing of affective and non-affective touch over left frontotemporal brain areas contralateral to the stimulated forearm in two-year-old children. Affective touch was administered by a single stroke with a soft brush over the child's right dorsal forearm at 3 cm/s, while non-affective touch was provided by multiple brush strokes at 30 cm/s. We found that in the insula, the total haemoglobin (HbT) response to slow brushing was significantly greater than the response to fast brushing (slow > fast). Additionally, a region in the postcentral gyrus, Rolandic operculum and superior temporal gyrus exhibited greater response to fast brushing than slow brushing (fast > slow). These findings confirm that an adult-like pattern of haemodynamic responses to affective and non-affective touch can be recorded in two-year-old subjects using DOT. To improve the accuracy of modelling light transport in the two-year-old subjects, we used a published age-appropriate atlas and deformed it to match the exterior shape of each subject's head. We estimated the combined scalp and skull, and grey matter (GM) optical properties by fitting simulated data to calibrated and coupling error corrected phase and amplitude measurements. By utilizing a two-compartment cerebrospinal fluid (CSF) model, the accuracy of estimation of GM optical properties and the localization of activation in the insula was improved. The techniques presented in this paper can be used to study neural development of children at different ages and illustrate that the technology is well-tolerated by most two-year-old children and not excessively sensitive to subject movement. The study points the way towards exciting possibilities in functional imaging of deeper functional areas near sulci in small children

Relationship between maternal pregnancy-related anxiety and infant brain responses to emotional speech – a pilot study

Background: Maternal pregnancy-related anxiety (PRA) is reportedly related to neurodevelopmental outcomes of infants. However, the relationship between maternal PRA and the processing of emotions in the infant brain has not been extensively studied with neuroimaging. The objective of the present pilot study is to investigate the relationship between maternal PRA and infant hemodynamic responses to emotional speech at two months of age.Methods: The study sample included 19 mother-infant dyads from a general sample of a population of Caucasian mothers. Self-reported Pregnancy-Related Anxiety Questionnaire (PRAQ-R2) data was collected from mothers during pregnancy at gestational weeks (gwks) 24 (N = 19) and 34 (N = 18). When their infants were two months old, the infants’ brains functional responses to emotional speech in the left fronto-temporoparietal cortex were recorded using diffuse optical tomography (DOT).Results: Maternal PRAQ-R2 scores at gwk 24 correlated negatively with the total hemoglobin (HbT) responses to sad speech on both sides of the temporoparietal junction (Spearman's rank correlation coefficient ρ = -0.87). The correlation was significantly greater at gwk 24 than gwk 34 (ρ = -0.42).Limitations: The field of view of the measurement did not include the right hemisphere or parts of the frontal cortex. The sample size is moderate and the mothers were relatively highly educated, thus there may be some differences between the study sample and the general population.Conclusions: Maternal pregnancy-related anxiety may affect child brain emotion processing development. Further research is needed to understand the functional and developmental significance of the findings.</p

Hemodynamic responses to emotional speech in two-month-old infants imaged using diffuse optical tomography

Emotional speech is one of the principal forms of social communication in humans. In this study, we investigated neural processing of emotional speech (happy, angry, sad and neutral) in the left hemisphere of 21 two-month-old infants using diffuse optical tomography. Reconstructed total hemoglobin (HbT) images were analysed using adaptive voxel-based clustering and region-of-interest (ROI) analysis. We found a distributed happy > neutral response within the temporo-parietal cortex, peaking in the anterior temporal cortex; a negative HbT response to emotional speech (the average of the emotional speech conditions angry in the anterior superior temporal sulcus (STS), happy > angry in the superior temporal gyrus and posterior superior temporal sulcus, angry <baseline in the insula, superior temporal sulcus and superior temporal gyrus and happy <baseline in the anterior insula. These results suggest that left STS is more sensitive to happy speech as compared to angry speech, indicating that it might play an important role in processing positive emotions in two-month-old infants. Furthermore, happy speech (relative to neutral) seems to elicit more activation in the temporo-parietal cortex, thereby suggesting enhanced sensitivity of temporo-parietal cortex to positive emotional stimuli at this stage of infant development.Peer reviewe

Vastasyntyneiden aivojen funktionaalinen lähi-infrapunaspektroskopia: Instrumentointi, menetelmät ja mittaukset

Near-infrared spectroscopy (NIRS) is a noninvasive medical technology that uses visible red and near-infrared light to probe changes in the concentrations of absorbers in tissue. In functional NIRS (fNIRS), local hemoglobin concentration changes in brain are measured, which can be interpreted as changes in cerebral blood flow and volume, and are related to neuronal activation. NIRS is an especially suitable imaging modality for neonates as the instrumentation is safe, portable and silent compared to, e.g., positron emission tomography and functional magnetic resonance imaging. Also, neonates are especially suitable subjects for fNIRS because of their small head size, thin scalp and skull and undeveloped myelination. In this Thesis, instrumentation and software for an optical tomography system were developed to improve the usability and data quality to allow fNIRS imaging of brain function in neonates and young infants. Also, measurement and data analysis methods were developed. The usability of the improvements was demonstrated by performing measurements of auditory evoked hemodynamic responses in neonates. Neuroscientific aims included the study of newborn brain function, the properties of hemodynamic responses and lateralization of speech and music processing.  The results of the Thesis show that neonatal brain studies with NIRS are feasible; NIRS can measure hemodynamic responses to stimulation and is well accepted by neonates. Hemodynamic responses to auditory stimuli were found to be changing rapidly around the time of birth and they correlate with sleep stage. The hemodynamic response to speech was found to be located on the left hemisphere already at the time of birth. This may be taken as an evidence that leftward lateralization of speech is already established at birth at least to some extent. The results also showed a large amount of inter-individual variations in hemodynamic responses in newborns. This is probably in part due to anatomical differences between individuals. A robust optical reconstruction method based on a realistic anatomical model of optical properties at the actual measurement area and a high-density measurement array is likely to reduce the variability and portray true responses more accurately. Monitoring of sleep stage, global systemic responses, and spontaneous hemodynamic oscillations should also be beneficial.Lähi-infrapunaspektroskopia (NIRS) on ei-invasiivinen lääketieteellinen tutkimusmenetelmä, joka hyödyntää punaista ja infrapunaista valoa kudoksen hemoglobiinikonsentraatioiden mittaamiseen. Funktionaalinen NIRS (fNIRS) mittaa aivotoiminnan aiheuttamia muutoksia aivokudoksen hapettuneen ja hapettumattoman hemoglobiinin pitoisuuksissa. NIRS soveltuu hyvin pienten lasten aivotutkimukseen, koska laitteisto on turvallinen, siirreltävä ja hiljainen. Vastasyntyneiden pään pienen koon, päänahan ja kallon ohuuden sekä aivojen vähäisen myeliinin määrän takia vastasyntyneet ovat myös erityisen soveltuvia koehenkilöitä fNIRS-tutkimukseen. Tässä väitöskirjatyössä kehitettiin optisen tomografian instrumentointia ja laiteohjelmistoja, mittaustekniikkaa sekä data-analyysimenetelmiä erityisesti vastasyntyneiden ja pienten lasten fNIRS-tutkimuksia varten. Työssä kehitettyä tekniikkaa, menetelmiä ja ohjelmistoja testattiin mittaamalla hemodynaamisia vasteita kuuloherätteisiin vastasyntyneillä koehenkilöillä. Mittausten neurotieteellisinä tavoitteina oli tutkia vastasyntyneiden aivotoimintaa, hemodynaamisen vasteen ominaisuuksia ja puheen sekä musiikin käsittelyn lateralisaatiota. Väitöstyön tulokset osoittavat fNIRS:n olevan käyttökelpoinen työkalu vastasyntyneiden aivotutkimukseen; menetelmällä voidaan mitata hemodynaamisia vasteita kuuloherätteisiin vauvaa turhaan rasittamatta. Mittaustulokset osoittivat hemodynaamisten vasteiden olevan erilaisia eri unitiloissa ja olevan nopean kehityksen vaiheessa raskausviikkojen 38–42 aikana. Tulosten mukaan hemodynaaminen vaste puheherätteeseen oli tilastollisesti merkitsevä vasemmalla aivokuorella, mikä viittaa puheen vasemman puoleisen lateralisaation olevan kehittynyt jo vastasyntyneillä. NIRS-tulokset osoittivat myös suurta vaihtelua yksilöiden välillä, mikä saattaa johtua anatomisista eroista. Anatomisesti realistiseen optiseen malliin perustuva rekonstruktio ja mittausten suurempi paikkaresoluutio saattaisi vähentää yksilöiden välistä vaihtelua ja kuvantaa vasteet tarkemmin. Myös unitilan, systeemisen verenkierron ja spontaanien oskillaatioiden huomioiminen analyysissä vähentää tulosten vaihtelua

Emotional Processing in the First 2 Years of Life : A Review of Near-Infrared Spectroscopy Studies

Emotional stimuli processing during childhood helps us to detect salient cues in our environment and prepares us for our social life. In early childhood, the emotional valences of auditory and visual input are salient and relevant cues of social aspects of the environment, and it is of special interest to understand how exactly the processing ofemotional stimuli develops. Near-infrared spectroscopy (NIRS) is a noninvasive neuroimaging tool that has proven valuable in studying emotional processing in children. After conducting a systematic search of PubMed, Web of Science, and Embase databases, we examined 50 NIRS studies performed to study emotional stimuli processing in children in the first 2 years of age. We found that the majority of these studies are done in infants and the most commonly used stimuli are visual and auditory. Many of the reviewed studies suggest the involvement of bilateral temporal areas in emotional processing of visual and auditory stimuli. It is unclear which neural activation patterns reflect maturation and at what age the emotional encoding reaches those typically seen in adults. Our review provides an overview of the database on emotional processing in children up to 2 years of age. Furthermore, it demonstrates the need to include the less-studied age range of 1 to 2 years, and suggests the use of combined audio-visual stimuli and longitudinal studies for future research on emotional processing in children. Thus, NIRS might be a vital tool to study the associations between the early pattern of neural responses and socioemotional development later in life.Peer reviewe