Empathy at birth: Mother's cortex synchronizes with that of her newborn in pain

Abstract

Early neonatal relation with the caregiver is vital for newborn survival and for the promotion of an appropriate neural development. The aim of this study was to assess if the empathic cortical response of a mother to her baby's pain is synchronized with the neonatal cortical response to the painful stimulation. We used hyperscanning, a functional neuroimaging approach that allows studying functional synchronization between two brains. Sixteen mother-newborn dyads were recruited. Maternal and neonatal cortical activities were simultaneously monitored, by near-infrared spectroscopy, during a heel prick performed on the baby and observed by the mother. Multiple paired t test was used to identify cortical activation, and wavelet transform coherence method was used to explore possible synchronization between the maternal and neonatal cortical areas. Activations were observed in mother's parietal cortex, bilaterally, and in newborn's superior motor/somatosensory cortex. The main functional synchronization analysis showed that mother's left parietal cortex activity cross-correlated with that of her newborn's superior motor/somatosensory cortex. Such synchronization dynamically changed throughout assessment, becoming positively cross-correlated only after the leading role in synchronizing cortical activities was taken up by the newborn. Thus, maternal empathic cortical response to baby pain was guided by and synchronized to the newborn's cortical response to pain. We conclude that, in case of potential danger for the infant, brain areas involved in mother-newborn relationship appear to be already co-regulated at birth.

Keywords: hyperscanning; interpersonal brain synchronization; mother-infant relationship; near-infrared spectroscopy; pain empathy.

FIGURE 1

Representation, on a schematic head, of optical fibre location: (a) on left and right side of mother's scalp and (b) on newborn's scalp. (Red dots: near‐infrared light emitters; blue dots: near‐infrared light detectors; numbered squares: channels. The international 10–20 EEG system reference points are also reported)

FIGURE 2

Oxyhaemoglobin (HbO₂) variation, reported on an error bar chart, during the three phases of the study (baseline, following disinfection and heel prick), in the three activated channels, when mothers were observing the painful stimulation performed on their own newborn (*P < FDR 0.05 compared to baseline). Channel's location is reported on a schematic head. Bars represent ±2 standard error variability around the mean (tick dash) of HbO₂ variation, which is reported on the y‐axis in mM•mm unit (see text)

FIGURE 3

Oxyhaemoglobin (HbO₂) variation, reported on an error bar chart, during the three phases of the study (baseline, following disinfection and heel prick), observed in the activated channel, when newborns were subjected to the painful stimulation (**P < FDR 0.05 compared with baseline; *P < 0.05 compared with baseline, but not surviving P < FDR 0.05 threshold). Channel's location is reported on a schematic head. Bars represent ±2 standard error variability around the mean (tick dash) of HbO₂ variation, which is reported on the y‐axis in mM•mm unit (see text)

FIGURE 4

Interpersonal brain synchronization, explored by wavelet transform coherence (WTC), between average time series of raw oxyhaemoglobin (HbO₂) signal from mother's left posterior parietal cortex (Channel 7) and baby's superior motor/somatosensory cortex (Channel 16), collected during the 20 s following heel prick. WTC value is encoded on a colour scale, as indicated on the right bar, and the significance level against noise (P < 0.05), obtained by Monte Carlo methods, is showed as a ticked contour surrounding frequency synchronized signals. Variations in arrow direction and inclination angle of frequency synchronized signals indicate that the relationship between these dyad's activated cortical areas slightly and progressively changed throughout synchronization periods. The interpersonal brain synchronization falling outside the cone of influence (the area of the figure with a lighter shade) results are unreliable (see text for details). Time series of average HbO₂ variation collected during the 20 following heel prick from mother's left posterior parietal cortex (Channel 7) and baby's superior motor/somatosensory cortex (Channel 16) are also represented on the bottom. HbO₂ variation is reported on the y‐axis in mM•mm unit (see text)

FIGURE 5

Interpersonal brain synchronization, explored by wavelet transform coherence (WTC), between average time series of raw oxyhaemoglobin (HbO₂) signal from mother's right posterior parietal cortex (Channel 18) and baby's superior motor/somatosensory cortex (Channel 16), collected during the 20 s following heel prick. WTC value is encoded on a colour scale, as indicated on the right bar, and the significance level against noise (P < 0.05), obtained by Monte Carlo methods, is showed as a ticked contour surrounding frequency synchronized signals. However, more than half of such interpersonal brain synchronization fell outside the cone of influence (the area of the figure with a lighter shade), thus resulting unreliable (see text for details). Time series of average HbO₂ variation collected during the 20 s following heel prick from mother's right posterior parietal cortex (Channel 18) and baby's superior motor/somatosensory cortex (Channel 16) are also represented on the bottom. HbO₂ variation is reported on the y‐axis in mM•mm unit (see text)

FIGURE 6

Interpersonal brain synchronization, explored by wavelet transform coherence (WTC), between average time series of raw oxyhaemoglobin (HbO₂) signal from mother's right anterior parietal cortex (Channel 19) and baby's superior motor/somatosensory cortex (Channel 16), collected during the 20 s following heel prick. WTC value is encoded on a colour scale, as indicated on the right bar, and the significance level against noise (P < 0.05), obtained by Monte Carlo methods, is showed as a ticked contour surrounding frequency synchronized signals. Some sparse significant coherences, in the band between 0.1 and 0.8 s (1.25–10 Hz) and all lasting no more than 2 a, could be observed. Time series of average HbO₂ variation collected during the 20 s following heel prick from mother's right anterior parietal cortex (Channel 19) and baby's superior motor/somatosensory cortex (Channel 16) are also represented on the bottom. HbO₂ variation is reported on the y‐axis in mM•mm unit (see text)