Current Biology
Volume 23, Issue 9, 6 May 2013, Pages 739-745
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Article
Infant Calming Responses during Maternal Carrying in Humans and Mice

https://doi.org/10.1016/j.cub.2013.03.041Get rights and content
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Highlights

  • Maternal carrying reduces crying, body movement, and heart rate of infants

  • In mice, a similar set of calming responses is observed during carrying

  • Mouse calming response requires proprioception and somatosensation

  • The calming responses in infants function to increase maternal carrying efficacy

Summary

Background

Mother-infant bonding is the earliest and most critical social relationship of mammalian infants. To promote this bond, infants have innate behaviors to seek maternal proximity and protest upon separation via communication with the mother vocally and through body movement. However, the physiological mechanisms regulating these infant behaviors remain largely undefined.

Results

Here we show a novel set of infant cooperative responses during maternal carrying. Infants under 6 months of age carried by a walking mother immediately stopped voluntary movement and crying and exhibited a rapid heart rate decrease, compared with holding by a sitting mother. Furthermore, we identified strikingly similar responses in mouse pups as defined by immobility and diminished ultrasonic vocalizations and heart rate. Using pharmacologic and genetic interventions in mouse pups, we identified the upstream and downstream neural systems regulating the calming response. Somatosensory and proprioceptive input signaling are required for induction, and parasympathetic and cerebellar functions mediate cardiac and motor output, respectively. The loss of the calming response hindered maternal rescue of the pups, suggesting a functional significance for the identified calming response.

Conclusions

Our study has demonstrated for the first time that the infant calming response to maternal carrying is a coordinated set of central, motor, and cardiac regulations and is a conserved component of mammalian mother-infant interactions. Our findings provide evidence for and have the potential to impact current parenting theory and practice, since unsoothable crying is the major risk factor for child abuse.

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These authors contributed equally to this work