Bowlby's bulb

Can a brain scan reveal your relationship to your mother? According to a recent study, this may well be the case.

One of the theories in modern psychology is about the relationship between a child and her parent, especially the mother. Among such attachment theories is the original theory by John Bowlby. For a good description of attachment theory see Wikipedia. There’s also a good article (PDF) in Developmental Psychology on the history of attachment.
Basically, the theory of attachment demonstrated that the dyadic relationship between the infant and the mother can take the form of different styles — attachment styles. Such styles include secure attachment where the infant can use the mother as a secure base from which the immediate environment is explored. Insecure attachment, however, can come in different forms, including avoidant, ambivalent and disorganized (see also here). Studies have shown that the attachment style at birth is likely to influence the social functions in adulthood, and that the attachment style in one female is inherited by her offspring through a process called transmission (see also this excellent paper). Normally, this transmission is thought to be socially transmitted, although I think it’s a dubious conclusion since children are both genetically and socially related to their mother. However, a convincing study (PDF) in 2003 by Bokhorst showed that while genetic influence on temperament was relatively high, the influence on attatchment style was negligible.

But let’s get to the case: does attachment style demonstrate measurable effects on the brain? Indeed, this is what Erwin Lemche and colleagues found in a study using functional MRI. Based on previous findings that insecure attachment is related to heightened sympathetic nervous system activity (e.g. heart rate increase and cortisol secretion), Lemche et al. demonstrated that performance during a stress, relative to a neutral, prime stimulus condition involved bilateral amygdalae activation.

The subjects were shownn two series of 32 sentence statements describing self-centred or other-centred information. They had to report whether they agreed or disagreed with the statements by pressing a button. Before the presentation of the target sentences, subliminal messages with negative content were presented on some occasions (stress condition), or with nonsense sentence content (neutral condition). For example, the negative prime could be “My mom rejects me” presented for 30 milliseconds. In the neutral condition the prime could be “Ym umu jrecest em”, also presented for 30 milliseconds.

The activation of the amygdalae after negative primes was the same for all subjects. However, for those subjects who demonstrated an insecure attachment style (determined by the Adult Attachment Interview) the amygdalae activation levels was significantly higher when presented with the unconscious negative primes.

So having an insecure attachment style leads to higher activation to attachment-related primes. Taken together, this result demonstrates a role for amygdala in mediating attatchment relevant behaviour. Indeed, it is interesting to see how a phylogenetic “old” limbic structure is involved in an interpersonal psychological process, which is normally thought to involve more prefrontal cortical regions.

-Thomas

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