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1 Threat Detection and Stress Reactivity: Development of Neurophysiological Subsystems

1 Threat Detection and Stress Reactivity: Development of Neurophysiological Subsystems

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5.1 Threat Detection and Stress Reactivity: Development …


Neurophysiological threat detection and stress reactivity. Underlying (and

integrated with) all these psychobehavioral systems are the neurophysiological

subsystems that trigger and coordinate stress reactivity. As described previously,

these include the sympathetic and parasympathetic nervous systems, the limbic–

HPA axis, and subcortical neurological subsystems, such as the amygdala (Gunnar

and Hostinar 2015; Gunnar and Quevedo 2007; Izard et al. 1987; Lupien et al.

2009; Ohman and Mineka 2001). Even though they are often studied separately,

these systems are integrated through the coordination of the variety of stress

“mediators” or “instruments” they produce. As explained by Joëls and Baram

(2009), “Any actual or potential disturbance of an individual’s environment—a

‘stressor’—is recognized or perceived by specific brain regions. The subjective

state of sensing potentially adverse changes in the environment is called ‘stress’ and

leads to the release of molecules that we here call ‘stress mediators’, which bind to

receptor targets. Each of these mediators acts on specific neuronal populations,

resulting in unique downstream effects. Together, these effects constitute the ‘stress

response’, which enables the animal to adapt to the changing environment”

(p. 459).

This system, described in more detail in Chap. 4, is complex. As Joëls and

Baram (2009) explain, it is highly differentiated, in that there are many different

stress mediators, including neurotransmitters (such as noradrenaline and serotonin),

peptides (such as corticotropin-releasing hormone and vasopressin), and steroid

hormones (such as cortisol). For coping researchers, it is of great interest to note

that each of these mediators is triggered by different features of a stressor (such as

its type—physical or social, duration, and context) depending on the state of the

organism (its age, sex, genes, and history). Each of these mediators also has its

characteristic, preferred spatial and temporal niches of action, so that the effects of

these mediators are differentiated as to both their exact timing (ranging from milliseconds to years) and the particular location of their effects (down to specific

segments of individual neurons).

At the same time, all these stress mediators are tightly integrated in their

functioning. There is overlap among their spatial and temporal niches, providing

opportunities for stress mediators to interact—by amplifying or dampening each

other’s effects and even by activating or de-activating other components of

underlying systems. Joëls and Baram (2009) argue that, “the diversity of the

instruments of stress, rather than being redundant, enables both optimal niches of

action for each mediator and interactions between the multiple mediators that

orchestrate our brain’s remarkable ability to respond—and adapt—to a dynamic

environment” (p. 459). They point out that, “[e]ach unique stress situation requires

an efficient response from numerous neuronal ensembles throughout the CNS, a

process that requires astute orchestration. This orchestration occurs through the

deployment of a repertoire of signaling molecules that can bring about the temporal,

spatial and context specificity of each individual stress response” (p. 459). The

complexity, variety, specificity, and sensitivity of the biobehavioral stress reactivity

system and the “neurosymphony of stress” means that at birth, neonates already


5 Development of “Coping” in Newborns …

have an exquisitely tuned set of instruments with which to respond to a wide range

of contextual and intrapsychic stressors.

Homeostatic and allostatic functions. In order to create a well-integrated

biobehavioral platform for the healthy development of coping, these neurobiological stress reactivity systems have to be able to flexibly adjust to the entire range of

demands—from the normal activities of daily living needed to survive, such as

eating, drinking, staying awake, and maintaining body temperature within acceptable limits; to opportunities for learning through constructive exploration, social

interaction, and play; to dealing with stressful events, such as obstacles, threats, and

danger. In fact, a general principle underlying the development of coping is that

energy for dealing with stress seems to come from the same stores as those that are

used to run the normal activities of daily living. Systems scientists like to call these

patterns of normal activity “homeostasis,” with the idea that living systems expend

a great deal of energy and activity just to maintain the state of “being alive.”

When thinking about the energy needed for dealing with extraordinary events,

which we call “stress” because they are out of the standard routines of daily life,

some systems scientists prefer the notion of “allostasis” (e.g., McEwen and

Wingfield 2010). It is actually a cumulative concept, because it refers to the energy

and activities needed to deal with regular daily routines plus those needed to deal

with stressful events. In terms of the development of coping, this means that more

energy will be available to work on coping and the development of new regulatory

resources, when less energy is required to deal with homeostatic demands (just as—

as discussed in Part IV—less energy will be available to work on the development

of coping, when more energy is required to deal with homeostatic demands).

In fact, as described in Chap. 4, the same neurophysiological systems that are

designed for dealing with challenges also have important functions in supporting

newborns during standard routine interactions. For example, the parasympathetic

nervous system (PNS) is heavily involved in releasing the sympathetic nervous

system (SNS, including heart rate, respiration, and blood pressure) to quickly

trigger vigilance and arousal when dealing with challenges, and it can also quickly

calm those same systems after stressors have passed. In addition to its role in upand down-regulating the SAM during and after stressful encounters, the PNS also

serves to maintain an alert and ready resting vagal tone during more routine

interactions. A high variable vagal tone is considered ideal for supporting sustained

attention and constructive engagement because it allows the neonate to be open and

responsive to opportunities to interact with social partners and to take advantage of

nonsocial forms of stimulation (Thayer et al. 2009). In fact, one of the earliest forms

of “exercise” for the vagal brake is during feeding (Porges and Furman 2011), when

the infant learns to release the brake while nursing (to provide energy for sucking

and swallowing) and then to reinstate the brake when done (to provide calm for

digestion). Both homeostatic and stress-related forms of regulation, and their

interconnections, are key to the development of adaptive parasympathetic systems.

The HPA axis also serves dual functions. As described previously, under

stressful conditions, it releases cortisol, which activates systems that can provide

energy for dealing with stress, and deactivates low priority systems (in charge of

5.1 Threat Detection and Stress Reactivity: Development …


immunity and reproduction); eventually, the HPA also down-regulates itself when

the stressor is terminated. At the same time, cortisol serves important functions in

maintaining available energy and arousal over the course of the day—waking up in

the morning and becoming sleepy at night. The regularity of diurnal cortisol

underlies the circadian rhythms of sleep–wake cycles and plays a permissive role in

the functioning of the SNS.

As can be imagined, these homeostatic and stress reactivity systems are inherently dynamic, in that to function adaptively, they need to be able to be flexible and

ready for a changing environment—to respond to current demands for maintaining

basic biological functions (sleep–wake, eat–digest, and so on) and also to maintain

states that encourage constructive engagement during social and nonsocial opportunities for interaction. Moreover, the systems also need to be ready to respond to

stressful demands with increased arousal and resources and then to be able to

recover from these episodes quickly.

Reorganization of stress neurophysiology at birth. Because these homeostatic

and allostatic neurophysiological functions are carried out within the mother’s body

during gestation, birth represents the beginning of a major reorganization in how

these tasks are accomplished (Nagy 2011; Porges and Furman 2011). It may seem

surprising, but the healthy development of coping depends upon the successful

resolution of this early developmental task, namely, the establishment of basic

homeostatic processes or regular biological rhythms (of breathing, eating, elimination, and sleep–wake cycles) outside the mother’s body (Kopp 1982). Hence, an

important precondition for the healthy development of coping in neonates is the

establishment of regular biorhythms. When these become entrusted to neurophysiological systems and so run relatively automatically, more energy should be

available for infants to deal with demands and challenges, which is where their

developing regulatory “muscles,” including those involved in coping, are exercised

and consolidated (Porges and Furman 2011).


Attachment, the Development of “External” Coping,

and the Omnibus Coping Strategy of “Proximity


Intact newborns do indeed come with complex and coordinated stress reactivity

systems, but if more elaborate coping is to be carried out during this developmental

period, that is, if intentional actions are to be taken to reduce stress or calm distress,

they will be undertaken, not by the newborn, but by caregivers, as described in

detail by researchers studying the attachment system (Ainsworth 1979; Bowlby

1969/1973; Carlson and Sroufe 1995; Kobak et al. 2006). As has been

well-established, the attachment system is a species-wide set of evolutionarily

adaptive mechanisms in which caregivers respond to infants’ distress or discomfort

by approaching and engaging with the infant. Acting in accordance with newborns’


5 Development of “Coping” in Newborns …

needs and expressed preferences, caregivers take action to calm and soothe the

infant or to change the stressful situation (e.g., by feeding a hungry infant, changing

a wet diaper, or moving the infant away from a loud noise).

Caregiver sensitivity as “external coping.” By definition, caregivers’ sensitive

responsiveness, comforting, and soothing serve to “cope” with the stressors

encountered by newborns (Fuertes et al. 2006; Nachmias et al. 1996). As has been

well documented, caregivers possess a wide variety of behaviors, including

skin-to-skin contact, holding, rocking, and cooing, that are effective in calming and

soothing infants. As a result, these have sometimes been referred to as “external

emotion regulation” (Conde-Agudelo et al. 2003; Feldman et al. 2002; Jahromi

et al. 2004; Kopp 1982). Animal and human studies also suggest that more subtle

forms of contact can act as “hidden regulators” (Hofer 1994), including maternal

feeding, body warmth, and tactile or sensorimotor stimulation (licking and

grooming); these are also effective in down-regulating the stress neurophysiology of

offspring (Gunnar and Quevedo 2007). Such soothing and comforting, along with

actually meeting newborns’ expressed needs, can also be considered forms of

“external coping” which create a local context of safety and comfort for the infant

(Hertsgaard et al. 1995). These experiences seem to be important foundations for

the infant’s ability to establish basic homeostatic functions as well as to modulate

physiological stress responses (Hostinar et al. 2014).

Emergence of proximity seeking as an omnibus coping strategy. Based on a

history of experience with the caregiver as an effective agent of “external coping,” a

crucial new omnibus coping strategy also emerges over the first few months of life,

namely, “proximity seeking” (Kobak et al. 2006; Sroufe 1996; Sroufe and Waters

1977). This stress response, to which humans and other mammals are predisposed,

relies on biobehavioral systems that are visible first in reflexes (grasping, huddling)

and crying and, then, based on sensitive caregiving, in intentional communications

and focused actions, such as looking, reaching, and distinctive vocalic patterns and

differentiated crying. The development of this umbrella coping strategy is an

essential step in shifting the nature of the neonates “coping” from neurophysiological to interpersonal.


Development of a Neurophysiological System

that Responds to “External Coping” by the Caregiver

An astonishing, and sometimes overlooked, capacity that is crucial to the healthy

development of coping also emerges at this same time, namely, the neonate’s

capacity to be comforted by trusted others (Hostinar et al. 2014). In order for

caregivers to become integral parts of an interpersonal coping system, newborns’

neurophysiology must develop the capacity to be calmed and soothed by the actions

of the caregiver. Porges and Furman (2011) explain how, from initially somewhat

one-sided interactions between caregiver and newborn, a neonatal

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