Mother rats show an elaborate pattern of stereotyped maternal behaviors as soon as the pups appear at the time of parturition. This pattern does not occur in virgin animals presented with foster pups, but it does occur in new mothers that have never encountered pups before and in the absence of specific practice. Over the past twenty-five years we have focused our efforts on understanding the mechanisms underlying this heightened responsiveness. Since we are basically psychologists we first evaluate behavior and then analyze underlying mechanisms, always keeping an eye on the behavior in question. Our approach has been to delineate the role of sensory factors, experience, hormones, and the brain in mediating the mother’s initial responses to her young as well as the long-term maintenance of her response, after the period of hormonal priming.
.....We are not fixated on any one paradigm, but use procedures and techniques as appropriate to the problem; we analyze the system from its most molar to its molecular levels. In order to study behavior we utilize a variety of tests of maternal behavior and maternal motivation, including behavioral observations of ongoing behavior, conditioned-place preference, operant responding for pup reinforcement, open field and hole-bored tests, and tests of attention (prepulse inhibition). In order to study the brain we use lesion and kindling techniques, as well as hormone and neurochemical replacement strategies to alter behavior; as well, we use traditional neuroanatomical histological procedures, immunocytochemistry, immunoflouresecnce, to assess changes in brain associated with behavioral manipulations. We have also begun an extensive series of studies in collaboration wityh Marla Sokolowski on the genetics of mothering using both gene expression profiles (through microarrays and gene sequencing and genotyping of candidate genes.
.....Within the past 10 years we have shifted our focus to development and we explore the role of experiences being mothered on the development of maternal behavior and its neurobiology in the offspring, and in the offspring’s offspring. Early experiences are manipulated by rearing pups without mothers (so-called pup-in-a-cup technique) and replacing mother-like olfactory, somatosensory, and thermal characteristics. We also use a variety of traditional ‘deprivation’ paradigms. Again this work requires the spectrum of behavioral, neurochemical, pharmacologic, and neuroanatomical techniques.
.....In addition to this rat work, we also study maternal behavior in humans. In Hamilton, Ontario, in collaboration with Dr. Meier Steiner, we study the sensory, endocrine, neural, and autonomic correlates of parental behavior in new mothers, new fathers, and teenage mothers. We adopt a psychobiological framework in our analyses of human behavior, often using the rat model as our point of departure. However, the strategy for the analysis of human behavior is necessarily different from the animal work, and involves in depth observations of ongoing behavior, questionnaire responses, visual analogue affect responses to infant cries and odors as well as measurements of salivary and plasma hormones and heart-rate. In recent work we have already started a series of fMRI studies on depressed and nondepressed mothers. Finally, as a collaborator in the M.A.V.A. N. project with colleagues in Toronto, Hamilton, and Montreal, we are also studying the genetics of mothering and the relation of mothering to infant development.
Our research is funded NSERC, MRC & NIMH.