Neurobiology of Infant Attachment

By Stephanie Moriceau & Regina M. Sullivan

Group 3, Week 9

Alicia IafonaroKimberly Villalva

Tawni Voyles

1. Explain what the HPA Axis is, the role it plays in psychological/brain function, and what psychological disorders it is connected with.

•The HPA axis is a set of biochemical pathways and the feedback reactions within them that result in interactions among the hypothalamus, pituitary gland, and the adrenal cortices that sit atop the kidneys.•The HPA axis controls reactions to stress and aids in regulation of many bodily processes, including digestion, the immune system, mood and emotion, sexuality, and energy storage/expenditure.

•This is important because of its clinical implications, as the HPA axis is involved in a wide variety of disorders, including:

• anxiety disorder•bipolar disorder•Insomnia and sleep disorder•PTSD

•borderline personality disorder•ADHD•major depressive disorder

A quick view of the HPA Axis:

Elevated levels of cortisol help the body sustain prolonged activity, but only at the expense of decreased immune system activity.

2. What is the neonatal CORT response? Explain what role it plays in attachment/sensitive period

learning.• Limits ability to express unlearned fear, learned odor

aversions (aka conditioned fear), passive avoidance, and inhibitory conditioning.

• These behaviors normally emerge at the end of the sensitive period, but can be delayed or advanced based on the CORT levels.

• Stress during early infancy may modify the neural systems

underlying attachment and later adult functioning of the same brain areas.

Figure 5Manipulated CORT levels on

learning during both sensitive period and post-

sensitive period• Injection of CORT

prevented the learning for shock-induced odor

• Injection prevented the achievement of the olfactory bulb learning- induced neural changes

• Decreased levels of CORT showed shock-induced odor preference learning and achievement of the olfactory bulb learning-induced neural changes

Paired Unpaired Odor

Paired Unpaired Odor

Paired Unpaired Odor

Paired Unpaired

CORT Saine CORT Saine

ADX SHAM ADX/CORT

ADX SHAM ADX/CORT

Figure 6Altered the development

expression of unlearned fear by manipulating the

CORT system.• Low levels of CORT block

pups expression of fear and attenuate amygdala activity

• Injection of CORT showed behavioral expression of fear

• Decrease of CORT hindered the normal expression of fear and the basolateral complex of the amygdala

3. What is shock-induced odor preference learning? Explain why you think this paradigm is useful.

Shock-induced odor preference learning• Classical conditioning paradigm when pups are

exposed to an odor while receiving either a shock or tail pinch.– Pups subsequently expressed a preference for that

odor

• This type of learning can be useful because the pups don’t learn to fear their mothers even when they are treated roughly. – They need to still have approach behaviors to get the mother’s milk

4. What happens when CORT levels are low, and is this a good thing?

• CORT levels are low for the first 10 days after rat pups are born.• Low CORT levels reduce amygdala activation in the rat pups.

• Sometimes the maternal rat will step on her pups in the nest or pull them towards her by their legs. The pups make a pain vocalization when this happens.

• By not being able to associate fear with their mother, they are likely guaranteed to accept her care regardless of its quality.

• This is thought to be adaptive because this way, the rat pups cannot learn to fear their caretaker.

• This is better for their survival during the ‘helpless infant’ stage seen by altricial species.

• The low levels of CORT are critical to ensure the olfactory-based attachment to the mother by the rat pups.

5. How do early life experiences impact adult life?

• They have an enormous impact on adult life in rodents, nonhumans, and humans.

• The overlap in brain areas associated with our attachment model and later psychiatric problems strongly suggests that the neonatal effects are mediated through the LC, amygdala, cerebellum, and HPA axis.

• Data suggests a potential mechanism for the enduring effects of early attachment on adult psychiatric wellness.

• Our life experiences, whether positive or negative, effect our experiences by altering the way we perceive things in the future and how we will react to them. – Ex. If someone experience a traumatic event their life would be altered by

those events, such as war or rape.

6. Summarize the findings discussed in this article• Pups exhibit enhanced preference learning and

attenuated aversion learning– Maternal odor preference learning is needed for survival and

blocking aversion learning that would interfere with pups’ attachment to the mother

• Beneficial for getting milk, huddling, and orientation• Pups neural circuitry underlying infant learning may have

evolved to ensure infants rapid attachment to the mother– Due to brain structures: olfactory bulbs, noradrenergic LC, lack

of amygdala participation• CORT levels are critical in determining characteristics of

early odor learning– Release in response to shock during the neonatal sensitive

period and attenuated CORT response limits ability to express unlearned fear, learn odor aversions , and inhibit conditioning