A Phenotype of Early Infancy Predicts Reactivity of the Amygdala in Male Adults

One of the central questions that has occupied those disciplines concerned with human development is the nature of continuities and discontinuities from birth to maturity. The amygdala plays a central role in the processing of novelty and emotion in the brain. While there is considerable variability among individuals in the reactivity of the amygdala to novel and emotional stimuli, the origin of these individual differences is not well understood. Four month old infants called high reactive (HR) demonstrate a distinctive pattern of vigorous motor activity and crying to specific unfamiliar visual, auditory, and olfactory stimuli in the laboratory. Low-reactive infants show the complementary pattern. Here we demonstrate that the HR infant phenotype predicts greater amygdalar reactivity to novel faces almost two decades later in adults. A prediction of individual differences in brain function at maturity can be made on the basis of a single behavioural assessment made in the laboratory at four months of age. This is the earliest known human behavioural phenotype that predicts individual differences in patterns of neural activity at maturity. These temperamental differences rooted in infancy may be relevant to understanding individual differences in vulnerability and resilience to clinical psychiatric disorder. Males who were HR infants showed particularly high-levels of reactivity to novel faces in the amygdala that distinguished them as adults from all other sex/temperament subgroups, suggesting that their amygdala is particularly prone to engagement by unfamiliar faces. These findings underline the importance of taking gender into account when studying the developmental neurobiology of human temperament and anxiety disorders. The genetic study of behavioral and biologic intermediate phenotypes (or “endophenotypes”) indexing anxiety-proneness offers an important alternative to examining phenotypes based on clinically-defined disorder. Because the HR phenotype is characterized by specific patterns of reactivity to elemental visual, olfactory, and auditory stimuli, well before complex social behaviors such as shyness or fearful interaction with strangers can be observed, it may be closer to underlying neurobiological mechanisms than behavioral profiles observed later in life. This possibility, together with the fact that environmental factors have less time to impact the four-month phenotype, suggests that this temperamental profile may be a fruitful target for high-risk genetic studies.Psycholog

Here Today, Gone Tomorrow? Changes in 4-Month-Olds' Physiologic and Behavioral Responses Do Not Indicate Memory for a Social Stressor

Although much is known about early memory development, only a few studies have explored infants' memory of social stress. While these few studies suggest that infants can remember stressful interactions, limitations seen in both methodology and statistical analyses give pause. In the current study, 4-month-olds and their mothers participated in both stressful and non-stressful interactions over 2 days. On Day 1, memory group infants participated in the double Face-to-Face Still-Face (FFSF) paradigm and control group infants participated in typical play. Both groups experienced the double FFSF paradigm on Day 2. Memory group infants exhibited the standard SF response but no differences in infant cortisol on Day 1. Both infant groups exhibited the standard SF response on Day 2. However, infants in the memory group, who saw the FFSF paradigm for the second time, did not demonstrate changes in cortisol or behavior indicative of memory across the 2 days. There was also no relationship between changes in cortisol and behavior for both days. The findings question the use of salivary cortisol as a measure of social stress and suggest that, although 4-month-olds reacted to the Still-Face social stressor immediately, they did not remember the following day

Infant temperament and anxious symptoms in school age children

A group of 164 children from different infant temperament categories were seen at 7 years of age for a laboratory battery that included behavioral and physiological measurements. The major results indicated that children who had been classified as high reactive infants at 4 months of age, compared with infants classified as low reactive, (a) were more vulnerable to the development of anxious symptoms at age 7 years, (b) were more subdued in their interactions with a female examiner, (c) made fewer errors on a task requiring inhibition of a reflex, and (d) were more reflective. Further, the high reactives who developed anxious symptoms differed from the high reactives without anxious symptoms with respect to fearful behavior in the second year and, at age 7 years, higher diastolic blood pressure, a narrower facial skeleton, and greater magnitude of cooling of the temperature of the fingertips to cognitive challenge. Finally, variation in magnitude of interference to fearful or aggressive pictures on a modified Stroop procedure failed to differentiate anxious from nonanxious or high from low reactive children

Do infants really have an implicit relational knowing?

Infants and their mothers use coherent communicative behaviors to co-regulate their interactions. Over time with repeated experiences of being together they create implicit relational procedures and knowing about the ways they engage with each other. Some of the ways are typical, such as an open handed wave, while others are unique to each mother-infant dyad, such as a particular finger game. The purpose of this study was to investigate infants’ individualized procedural communicative behaviors as strategies for eliciting mothers’ typical response during the Still-Face Paradigm (FFSF). In particular, we aimed to observe 1) the dyadic unique interactive behaviors exhibited by the infant in a normal playful interaction, and 2) whether the unique interactive behaviors are then utilized as eliciting behaviors (UEBs) in a perturbated interactive context, when the mother is acting in an unresponsive manner (Still Faced). 86 mother-infants dyads were observed in the FFSF at one of two different ages: 24 and 43 weeks of age. Play Episode and Still-Face Episode were coded by two independent coders to identify dyadic unique interactive behaviors in the Play Episode, and the same dyadic unique interactive behaviors displayed by the infants in the Still Face episode. Results showed that only the 43-weeks old babies displayed UEBs (29.3%) whereas no UEBs were observed in the 24-weeks old infants, pointing to an important early developmental difference, χ2 (1, N=119) = 25.390, p < 0.001. When comparing across age groups, older infants were more likely to show UEBs than younger infants. These findings suggest that infants acquire UEBs with repetitions of typical interactions with their caretaker and are able to make use of these behaviors with the development of different capacities (cognitive, motor, emotional), in an attempt to elicit a response from an unresponsive mother UEBs can be incorporated into a procedural relational knowledge, which can then be used for different purposes in a different context. This research contributes to the understanding of implicit relational knowing as a form of procedural knowledge that arises in the interactional processes between infants and caregivers