REVIEW ARTICLE Neuroendocrinology of Parental Response to Baby-Cry J. E. Swain*, P. Kim and S. S. Ho* *Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA.  National Institutes of Mental Health (NIMH), Bethesda, MD, USA. Introduction Parenting is critical for an infant’s survival and development across mammalian species. Despite increased levels of stress as a result of physiological, emotional and economical demands from the baby (1), parents typically find themselves highly motivated to take care of their infants’ needs and also find the interactions with infants rewarding (2,3). The present review draws upon recent human and animal brain research using infant stimuli to examine psychological and biological aspects of maternal motivations and behaviours. Using the example of selected maternal brain and endocrine responses to the hunger cry of an infant, we examine the modula- tory roles of dopamine (DA), oxytocin (OT), cortisol (CORT) and endogenous opioids (EO). Thus, we propose to build on current bio- behavioural parental brain models (4,5) for a simplified and inte- grated homeostatic neuroendocrine model. Neuroimaging methodology primer Functional neuroimaging methods relevant to the present review include magnetic resonance imaging (MRI) and positron emission tomography (PET). MRI techniques combine non-invasive magnetic fields and radiofrequency signals for millimetre resolution. Voxel- based morphometry detects changes in brain structure as a result of development or the environment. Functional MRI (fMRI) involves blood-oxygenation-level-dependent (BOLD) measurements that reflect changes in neural activity over a time resolution of seconds. Typically, BOLD signals during different events are measured throughout the brain. Subsequent analyses identify brain regions that show greater activity in response to a condition of interest (e.g. own-baby-cry versus other-baby-cry) and allow correlation of such brain activity with measures of parental behaviours. This tech- nique can also be carried out in rats using such stimuli as nipple suckling, along with direct neurohormone sampling. PET represents another functional brain imaging technique for humans, and mea- sures certain receptor-specific changes in radioactive tracers injected into the bloodstream but with the caveats of radiation exposure and longer minute-scale temporal resolution. Several caveats of current brain imaging must be considered. First, the BOLD signals of the fMRI data are indirect measures of neural activity, such that the data are susceptible to non-neural changes in the participant’s body and environment. Second, imag- ing data provide information on the association, rather than causality, between brain and behaviour. Third, because of the Journal of Neuroendocrinology Correspondence to: J. E. Swain, Department of Psychiatry, University of Michigan, 4250 Plymouth Road, Ann Arbor, MI 48109-2700, USA (e-mail: jamesswa@med.umich.edu). This overview attempts to synthesise current understandings of the neuroendocrine basis of par- enting. The parent–infant bond is central to the human condition, contributes to risks for mood and anxiety disorders, and provides the potential for resiliency and protection against the devel- opment of psychopathology. Animal models of parenting provide compelling evidence that bio- logical mechanisms may be studied in humans. This has led to brain imaging and endocrine system studies of human parents using baby stimuli and concerted psychological and behaviour- al measures. Certain brain circuits and related hormonal systems, including subcortical regions for motivation (striatum, amygdala, hypothalamus and hippocampus) and cortical regions for social cognition (anterior cingulate, insula, medial frontal and orbitofrontal cortices), appear to be involved. These brain circuits work with a range of endocrine systems to manage stress and motivate appropriate parental caring behaviour with a flexibility appropriate to the environment. Work in this field promises to link evolving models of parental brain performance with resilience, risk and treatment toward mother–infant mental health. Key words: parent–child relationships, brain imaging, functional magnetic resonance imaging, attachment, parenting, caregiving, cortisol, dopamine, opioids. doi: 10.1111/j.1365-2826.2011.02212.x Journal of Neuroendocrinology 23, 1036–1041 ª 2011 The Authors. Journal of Neuroendocrinology ª 2011 Blackwell Publishing Ltd Journal of Neuroendocrinology From Molecular to Translational Neurobiology