Transport Response is a filial-specific behavioral response to maternal carrying in C57BL/6 mice

Abstract

BackgroundA mother carries her young in many altricial mammals, such as cats, lions, rats and mice. During maternal carrying, the transported young assume a compact posture. We have recently shown that, in both humans and mice, the carried infants immediately calmed down and showed reductions in heart rate, distress vocalizations, and voluntary movement. The loss of the calming response in mouse pups hindered maternal retrieval efficacy. These findings suggested that the infant calming response functioned to reduce the maternal burden of carrying and was therefore conserved in a variety of mammalian species. However, it remains unclear how and when each component of this calming response develops and whether it is a filial-specific behavior.ResultsWe dissected various components of the carrying-induced responses in mouse pups, collectively called the “Transport Response” herein. We showed that during the second postnatal week, pups exhibited characteristic compact posture with limb ventroflexion. The body trunk remained paradoxically pliable, suggesting complex neural regulation throughout the body. Pups also showed an increased pain tolerance to a tail pinch during the Transport Response. Analyses of the developmental courses of distinct components of the Transport Response revealed the independent regulation of each component: in the first postnatal week, the cessation of ultrasonic vocalizations was exhibited prominently; in the second postnatal week, immobilization reached its peak; and toward the third postnatal week, the postural component became fully matured. At the end of the third postnatal week, when the pups are able to transport by themselves, the pups no longer exhibited the Transport Response.ConclusionsThis study has revealed the mouse Transport Response as a complex set of behavioral and physiological components, each of which has a specific postnatal time window but is orchestrated in a well-matched manner with the maturation of ambulatory ability in the pups. These findings collectively indicate that the Transport Response is a filial-specific, innate behavioral reaction and is distinct from a simple reflex or defensive freezing response. The Transport Response could be a novel index of primitive filial attachment behaviors, acting to smooth mother-infant interaction.

The calming effect of maternal carrying in different mammalian species

“…New studies have investigated maternal retrieval behavior and pup’s calming response from a different perspective, examining them as a mutually dependent, dynamic process ( Esposito et al, 2012 , 2013 ; Yoshida et al, 2013 ). To explore this dyadic interaction in detail, we created a new experimental task of “maternal rescue of pups from a cup” (see Figure 2A ), which is meant to mimic a challenging situation in the wild.…”

Theory of Mind: Towards an Evolutionary Theory

“…The new state of mind could best be described as a deep tranquilization or hypnotic trance. Thus, it seems as though evolution has reused the stereotypic behavior of prey, as they are carried away in their captor's jaws, in the service of childrearing (Prestrude 1977;Brewster and Leon 1980;Webster et al 1981;Meyer et al 1984;Yoshida et al 2013;Esposito et al 2015). 8 Comparable reactions have been observed in human infants that are posturally inverted and rhythmically stimulated (Peiper 1963;Krojanker 1969;Vrugt and Pederson 1973).…”

“…Peiper 1963;Krojanker 1969;Vrugt and Pederson 1973;Yoshida et al 2013;Esposito et al 2015). 43 This relaxed mode of being, mostly spent in a supine position, plays an important role in their subsequent cognitive development.…”

How Can I Make My Younger Sibling Stop Crying?

“…Instead, the mother mouse uses her mouth to grasp a bit of skin at the back of the mouse pup's neck (Figure 2). Researchers were able to recreate this grip by pinching this same spot [3][4][5][6]. This way, the researchers had more control over the experiment.…”