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This is intriguing research about variations in the dopamine (‘reward’) gene and its potential influence on variations in patterns of attachment NON abused infants can display. The research used Ainsworth’s Strange Situation test of attachment, and report discovery of a definite genetic link that can create Disorganized insecure attachment patterns in infants that (according to researchers) otherwise experience a safe and secure early attachment environment with their caregiver.
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By Lakatos et. al., Molecular Psychiatry (2000) 5, 633-637., Hungry
“About 15% of one-year-old infants in non-clinical, low-risk and up to 80% in high-risk (eg maltreated) populations show extensive disorganized attachment behavior12 in the Strange Situation Test.3 It has also been reported that disorganization of early attachment is a major risk factor for the development of childhood behavior problems.4 The collapse of organized attachment strategy has been explained primarily by inappropriate caregiving, but recently, the contribution of child factors such as neurological impairment5 and neonatal behavioral organization6 has also been suggested. Here we report an association between the DRD4 III exon 48-bp repeat polymorphism and attachment disorganization. Attachment behavior of 90 infants was tested in the Strange Situation and they were independently genotyped for the number of the 48-bp repeats by polymerase chain reaction (PCR). The 7-repeat allele was represented with a significantly higher frequency in infants classified as disorganized compared to non-disorganized infants… The estimated relative risk for disorganized attachment among children carrying the 7-repeat allele was 4.15. We suggest that, in non-clinical, low-social-risk populations, having a 7-repeat allele predisposes infants to attachment disorganization.”
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By Gervai et. al., American Journal of Medical Genetics Part B (Neuropsychiatric Genetics) 132B:126–130 (2005), Hungary
This article talks about how a variation in a D4 dopamine gene “may act as a resilience factor in the optimal development of early attachment” although researchers report “we can only speculate about mechanisms through which the polymorphism of the DRD4 gene may affect the development of infants’ attachment behavior. The DRD4 gene is expressed in the prefrontal cortex (PFC) which is richer in dopamine than any other region of the cerebral cortex. Prefrontal cortex and dopamine play a role in attention, working memory and reward-related learning, as well as negative emotionality, social withdrawal, and sensitivity to stressful situations…. The level of dopamine and the density of dopamine receptors in PFC are increasing between 6 and 12 months of infant life, when many of these functions go through intensive development. This period is also crucial for the development of first attachment relationships….. Learning processes during the infant’s first year of life involving the prefrontal cortex might be influenced by the DRD4 genotype through perceiving and reacting to environmental (caregiving) stimuli and stressful situations differently. Evidence is accumulating from separate studies of inter-relationships among genetic factors, distress regulation, attention, brain activity and attachment….” (page 4)
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This replicated study DID NOT find the genetic association:
Authors: M. J. Bakermans-Kranenburg; M. H. Van Ijzendoorn — Attachment & Human Development, Volume 6, Issue 3 September 2004 , pages 211 – 218
| Abstract
“In a first molecular genetic study Lakatos and colleagues found an association between attachment disorganization and the dopamine D4 receptor (DRD4) gene polymorphism, in particular in the presence of the -521 T allele in the promoter region of the DRD4 gene. Replication of their study in a sample of 132 infants did not confirm the role of the DRD4 7+ -allele and the -521C/T promoter gene in disorganized attachment. Although our sample was larger, and contained more children with CT or TT alleles, which enhanced the probability of finding the DRD4 and C/T interaction, the association was not found. Even when we combined our sample with the Lakatos sample, the interaction effect of the DRD4 and -521 C/T polymorphisms on disorganized attachment was absent.” |
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Here is a very nice online presentation of the basics regarding the assessment of infant attachment:
Is your child securely attached? The Strange Situation test (2008) By Gwen DeWar
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And this research, of course, is fascinating!
What’s in a Smile? Maternal Brain Responses to Infant Facial Cues
Lane Strathearn, MBBS, FRACP, Jian Li, PhD, Peter Fonagy, PhD, P. Read Montague, PhD — PEDIATRICS Vol. 122 No. 1 July 2008, pp. 40-51 (doi:10.1542/peds.2007-1566)
(free full text online by clicking on article title)
“OBJECTIVES. Our goal was to determine how a mother’s brain responds to her own infant’s facial expressions, comparing happy, neutral, and sad face affect.
METHODS. In an event-related functional MRI study, 28 first-time mothers were shown novel face images of their own 5- to 10-month-old infant and a matched unknown infant. Sixty unique stimuli from 6 categories (own-happy, own-neutral, own-sad, unknown-happy, unknown-neutral, and unknown-sad) were presented randomly for 2 seconds each, with a variable 2- to 6-second interstimulus interval.
RESULTS. Key dopamine-associated reward-processing regions of the brain were activated when mothers viewed their own infant’s face compared with an unknown infant’s face. These included the ventral tegmental area/substantia nigra regions, the striatum, and frontal lobe regions involved in (1) emotion processing (medial prefrontal, anterior cingulate, and insula cortex), (2) cognition (dorsolateral prefrontal cortex), and (3) motor/behavioral outputs (primary motor area). Happy, but not neutral or sad own-infant faces, activated nigrostriatal brain regions interconnected by dopaminergic neurons, including the substantia nigra and dorsal putamen. A region-of-interest analysis revealed that activation in these regions was related to positive infant affect (happy > neutral > sad) for each own–unknown infant-face contrast.
CONCLUSIONS. When first-time mothers see their own infant’s face, an extensive brain network seems to be activated, wherein affective and cognitive information may be integrated and directed toward motor/behavioral outputs. Dopaminergic reward-related brain regions are activated specifically in response to happy, but not sad, infant faces. Understanding how a mother responds uniquely to her own infant, when smiling or crying, may be the first step in understanding the neural basis of mother–infant attachment.” (bold type is mine)
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Stop the Storm 