Upon this background, the pups responded to a natural maternal odour or an artificial odour that was conditioned as a new maternal odour through pairings with either a positive stimulus (the stroking) or a negative stimulus (the shock). Exposure to both their mother's natural scent and the conditioned maternal scent evoked normal social responses, including those related to attachment.
The authors also evaluated the impact of raising the pups' levels of the stress hormone corticosterone, or being reared with an abusive mother. In these cases, pups with an abusive attachment showed disrupted social behaviour with the mother and increased engagement of the amygdala, a region of the brain involved in regulating stress and emotion.
"Our work shows that, while the infant brain is wired to form attachments at all costs, abusive attachments have negative consequences in social behaviour development," explained Dr Raineki. "Most importantly, some effects of early life abuse may be hidden until the abused animal is challenged and the negative effects are uncovered."
Dr. John Krystal, Editor of Biological Psychiatry, also commented, "It is interesting that the amygdala is primarily activated when abusive behaviour of the mother is combined with a reaction within the infant, i.e., an increase in levels of the stress hormone corticosterone. Thus, the authors of this study elegantly highlight the dyadic nature of the mother-infant relationship."
Using this model of attachment may provide clues to understanding attachment in children with various conditions of care. The authors hope that this model will help us understand the neurobiological origins of psychopathology stemming from abuse, and possibly facilitate the development of treatments and/or interventions for victims of early-life trauma.
The article is "Developing a Neurobehavioral Animal Model of Infant Attachment to an Abusive Caregiver" by Charlis Raineki, Stephanie Moriceau, and Regina M. Sullivan. The authors are affiliated with the Emotional Brain Institute, Nathan Kline Institute for Psychiatric Research, Orangeburg, New York; the Child Study Center, Child and Adolescent Psychiatry, New York University Langone Medical Center, New York, New York; the Center for Neural Science, New York University, New York, New York; and, the Department of Zoology, University of Oklahoma, Norman, Oklahoma. The article appears in Biological Psychiatry, Volume 67, Issue 12 (June 15, 2010), published by Elsevier.
The authors' disclosures of financial and conflicts of interests are available in the article.
John H. Krystal, M.D. is Chairman of the Department of Psychiatry at the Yale University School of Medicine and a research psychiatrist at the VA Connecticut Healthcare System. His disclosures of financial and conflicts of interests are available here.