Neural circuits underlying crying and cry responding in mammals

Abstract

Crying is a universal vocalization in human infants, as well as in the infants of other mammals. Little is known about the neural structures underlying cry production, or the circuitry that mediates a caregiver's response to cry sounds. In this review, the specific structures known or suspected to be involved in this circuit are identified, along with neurochemical systems and hormones for which evidence suggests a role in responding to infants and infant cries. In addition, evidence that crying elicits parental responses in different mammals is presented. An argument is made for including 'crying' as a functional category in the vocal repertoire of all mammalian infants (and the adults of some species). The prevailing neural model for crying production considers forebrain structures to be dispensable. However, evidence for the anterior cingulate gyrus in cry production, and this structure along with the amygdala and some other forebrain areas in responding to cries is presented.

Figure 1

Spectrographic examples of infant cries in two primate species. These illustrate the two types of infant cry in mammals. Left) Click emitted by Garnett’s greater bushbaby (Otolemur garnetti) after being deposited on a branch by its mother at 4 days of age. Right) Coo (‘tonal’ cry) following brief maternal separation in rhesus macaque (Macaca mulatta) at 14 days of age.