mise à jour du
23 octobre 2002
Nature Reviews Neuroscience
2001; 2; 2; 129
The neurobiology of attachment
Thomas R Insel and Larry J Young
Center for behavioral Neuroscience, Emory University, Atlanta, Georgia
sur le site Nature Reviews Neuroscience
Sniff yawning in bovinae Von Halder & Schenkel
Attachment behaviour is both biologically important and technically difficult to study. The behaviour is complex and there are changes in several cognitive and affective variables to consider.Nevertheless, recent studies with chicks, rats, sheep, voles and now humans have begun to reveal some important candidates for the neurobiology of social attachment.

The neuropeptides oxytocin and vasopressin have yielded a model that links molecular, cellular and systems approaches. Dopamine pathways in the forebrain, especially the nucleus accumbens and ventral pallidum, seem to be important for certain aspects of partner preference formation. It seems likely that for attachment to occur, these neuropeptides must link social stimuli to dopamine pathways associated with reinforcement.

It is also possible that neural mechanisms that we associate with drug abuse and addiction might have evolved for social recognition, reward and euphoria,critical elements in the process of attachment. In the very near future,we can hope that discoveries of the molecular and cellular mechanisms of addiction might be applied to the neurobiology of attachment, providing a new understanding of one of our most complex and intriguing emotions.

Of human bonding

Are animal studies of attachment relevant to human love? In the human brain, oxytocin receptors are concentrated in several dopamine-rich regions, especially the substantia nigra and globus pallidus, as well as the preoptic area.Whereas this pattern is consistent with a monogamous brain, the receptors are not found in the ventral striatum or ventral pallidum, areas in which either oxytocin or vasopressin V1a receptors are abundant in monogamous voles and monkeys. There is no evidence, at this time, that these pathways are involved in human attachment. A recent functional magnetic resonance imaging (fMRI) study of adults looking at pictures of their partners, as opposed to close non-romantic friends, found bilateral activation in the anterior cingulate (Brodmann's area 24), medial insula (Brodmann's area 14) as well as caudate and putamen. The pattern of cortical activation was distinct from previous studies of face recognition, visual attention, sexual arousal or other emotional states, but resembled preliminary results from an fMRI study of new mothers listening to infant cries. Both studies of human attachment show marked overlap between the pattern of activation when looking or hearing a loved one and a previous report of activation during cocaine-induced euphoria. It seems likely that pathways that mediate the hedonic properties of psychostimulants evolved as neural systems for social attachment.

Graves, F. C., K. Wallen, et al. "Opioids and attachment in rhesus macaque (Macaca mulatta) abusive mothers." Behav Neurosci (2002). 116(3): 489-93.
This study investigated the role of the endogenous opioid system in maternal and affiliative behavior of group-living rhesus macaque (Macaca mulatta) mothers with a history of abusive parenting. Eighteen mothers received an injection of the opioid antagonist naltrexone or saline for 5 days per week for the first 4 weeks of the infant's life. After treatment, mother-infant pairs were focally observed. Naltrexone did not significantly affect infant abuse or other measures of maternal behavior. Naltrexone increased the amount of grooming received by mothers from other group members and reduced the mothers' rate of displacement activities such as scratching, yawning, and self-grooming. These results concur with previous primate studies in suggesting that opioids mediate the rewarding effects of receiving grooming and affect anxiety-related behaviors.