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1 Neuroanatomical Systems involved in Stress Reactivity, Regulation, and Coping

1 Neuroanatomical Systems involved in Stress Reactivity, Regulation, and Coping

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4 Neurophysiological Developments that underlie Age-related …



punishment; the recognition, processing, and regulation of emotion; maintenance of

engagement and goal pursuit; attention regulation and cognitive control; flexible

adaptation to environmental conditions; and self-conceptions and understanding.

All of the neurophysiological processes underlying these activities are implicated in

the kinds of stress reactivity and action regulation that comprise coping. Coping

adaptively depends on threat detection and resource mobilization that are

well-calibrated to actual conditions. Constructive action regulation under stress

depends on focused and flexible attention, the capacity to understand and modulate

emotions (both amplification and dampening), and the ability to intentionally

deploy strategic and goal-directed behavior (including inhibition). In fact, many of

the most common adaptive coping responses—problem-solving, direct and planned

action, information-seeking and negotiation, and cognitive reappraisal—depend on

executive attention and cognitive control (i.e., executive functions). Flexible

attention deployment can assist with the ability to shift focus, reappraise, and use

cognitive distraction when under stress, and cognitive control allows for flexible

decision-making and action in the face of strong feelings.

Decades of research in attentional, emotional, and cognitive development, as

well as findings emerging from the relatively newer fields of cognitive and social

neuroscience, have provided a sound base of evidence for understanding human

stress reactivity, threat detection, executive attention, emotion regulation, and

cognitive control as parts of a complex dynamic system involving multiple levels of

interacting processes (LeDoux 1995; Lewis et al. 2006; Thayer and Lane 2000,

2009; Zeman et al. 2006). Compared to work in these areas, however, research on

coping has only just begun to look directly at its neurophysiological underpinnings

(Compas 2006). And findings on the neurological bases of reactivity, regulation,

and executive functions have not yet tied the functioning of these brain circuits

directly to coping, in that little of this research explicitly addresses how these

processes might shape the ways children and adolescents respond to and cope with

stressors in the real world. However, “developmentally-friendly” conceptualizations

of coping that explicitly focus on threat detection, stress reactivity, and action

regulation under stress as basic component processes make it easier to draw from

current neurophysiological work in order to specify the biological foundations of

coping (Compas 2006). As pictured in Fig. 4.1, when coping is seen as a

multi-level biopsychosocial process, then the processes operating on the psychological level, including the attentional, emotional, motivational, and cognitive

subsystems involved in stress reactivity and regulation, can point to the kinds of

neurobiological processes that likely underlie coping and shape its development.



4.1.1



Neurophysiology of Stressful Encounters



Although more research is needed, there is an emerging model of how neuroanatomical systems and circuitry work in concert and over time when stress is

encountered. When the brain detects a threat, a coordinated physiological response



4.1 Neuroanatomical Systems involved in Stress Reactivity, Regulation, and Coping



65



Fig. 4.1 Integrative multi-level conceptualization of coping as a biopsychosocial system that

incorporates processes from three levels: (1) the neurophysiological level, including psychobiological subsystems used to detect and react to stress and to regulate stress reactivity, most

centrally the sympathetic–adrenal–medullary (SAM) axis, the parasympathetic nervous system

(PNS), the hypothalamic–pituitary axis (HPA), the amygdala, and the prefrontal cortex (PFC),

especially the anterior cingulate cortex (ACC); (2) the psychological level, including the

attentional, emotional, and motivational subsystems involved in stress reactivity and regulation;

and (3) the level of action, including the behavioral, cognitive, and meta-cognitive subsystems that

jointly generate action tendencies and that integrate and regulate them



involving autonomic, neuroendocrine, metabolic, and immune system components

is activated. Research has revealed that the regions of the brain and other biological

systems involved in stress responses are the same regions and systems that tend to

be involved in coping, as well as the same systems involved in self-regulation and

adaptation more generally (Compas 2004; Etkin et al. 2011). For example, evidence



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4 Neurophysiological Developments that underlie Age-related …



from studies using responses to pictures of human faces showing emotion (Goldin

et al. 2009; Killgore and Yurgelun-Todd 2005; McClure et al. 2007; Stein et al.

2002; Straube et al. 2004; Yoon et al. 2007) or from studies that require participants

to give a speech (Furmark et al. 2002; LeDoux 2000; Tillfors et al. 2001) reveals

that stress and emotional reactivity depend on limbic regions, including the ACC,

amygdala, and insula. Moreover, such research identifies multiple PFC regions that

are involved in emotion processing, intensity, and regulation (Etkin et al. 2011;

Grimm et al. 2006). At the same time, the PFC has multiple regions important for

cognitive control, and the amygdala plays an essential role in attention, which has

been described as a gatekeeper that allows for further processing of information

deemed relevant to a goal (Oschner and Gross 2007).

As mentioned previously, the neurophysiological systems most central to threat

detection, stress reactivity, and regulation, which are basic to human survival and to

coping, include the SAM system, the PNS, the HPA axis, the amygdala, the hippocampus, and the PFC, including the ACC (Gunnar and Quevedo 2007; Lupien

et al. 2009; Porges and Furman 2011; Romeo 2010; Sapolsky et al. 2000). The

general functioning of each subsystem is touched on briefly below, and then more

detail is provided in subsequent sections depicting how each subsystem develops.

The autonomic nervous system (ANS). The ANS, which innervates most

internal organs and bodily systems, is centrally involved in orchestrating the fundamental stress responses of freeze, fight, and flight, as well as facilitating recovery

from stress. It consists of two branches, the sympathetic nervous system (SNS) and

the PNS, which generally have antagonistic or compensatory effects. The SNS, or

the SAM axis, subserves the most rapid responses to stress. It functions to swiftly

mobilize metabolic resources and orchestrate fight/ flight responses. Quick release

of catecholamines (i.e., epinephrine or adrenaline) from the medulla of the adrenal

gland to major organs produces immediate physical effects, including increases in

heart rate, stroke volume, and blood pressure; increases in respiration rate; increases

in blood glucose; dilation of blood vessels to muscles, and constriction of blood

flow to skin and digestive organs. Together, these effects activate the entire body,

for example, bringing blood and glucose to the muscles, and ready it for both

escape behaviors (flight) and defensive reactions (fight). In response to psychosocial threats, its role is to increase arousal, support vigilance, and narrow attention.

The SAM also helps to activate the other arm of the neuroendocrine stress-response

system, the HPA axis.

The PNS plays two primary roles during stressful encounters. First, it plays a

compensatory role with respect to the SAM, so that its suppression allows the SAM

to orchestrate its many short-term stress responses. Second, when a stressful event

has passed, the parasympathetic system down-regulates the SAM, allowing the

individual to calm and equilibrium to be reinstated. The PNS accomplishes both

these functions through the “vagal brake” (i.e., the 10th cranial nerve or the vagus

nerve), which connects the nucleus ambiguus (NA) in the brain stem to the

sinoatrial node of the heart. This vagal circuit typically maintains the SNS at a rate

below its intrinsic pacemaker. When organisms encounter challenges, however, the

PNS releases the vagal brake and the heart accelerates instantly (along with blood



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pressure, respiration, and other autonomic functions) to provide additional resources for vigilance and action; when the stressor has resolved, the PNS resets the

vagal brake which allows the heart rate (and other autonomic functions) to quickly

return to normal, conserving resources and supporting routine functioning.

As explained by Porges and Furman (2011),

Changes in RSA [respiratory sinus arrhythmia or vagal tone] represent a dynamic adjustment of the inhibitory action of the vagus (‘vagal brake’) on the heart. Functionally, the

removal of the vagal brake provides a physiological state that promotes vigilance as an

intermediary and precautionary psychological process to monitor risk in the environment.

The outcome of this assessment includes the induction of different physiological states,

either in which social behaviours can proceed, or in which defensive fight-flight strategies

associated with increased sympathetic excitation are necessary. If defensive behaviours are

not necessary to maintain or to negotiate safety, then the rapid vagal regulatory mechanisms

that dampen autonomic state are reinstated, allowing the individual to calm and self-soothe.

(p. 116)



Although not mentioned as frequently in discussions of the PNS, the dorsal

vagal complex also plays a third role in stressful encounters, namely, to induce

stress responses that involve immobilization (i.e., the “freeze” response). The

vegetative (or unmyelinated) vagus exerts an effect on reflexive cardiac activity;

this immediately decelerates the heart rate, resulting in complete stillness, accompanied by the orienting of attention toward the threat. Sometimes called the “reptilian circuit,” this seems to be the phylogenetically oldest and earliest developing

stress reactivity system, and may have been preserved because, through its effects

on passive avoidance, it made mammals less visible to predators (Porges and

Furman 2011).

Hypothalamic–pituitary–adrenal (HPA) axis. The activity of the HPA axis,

like that of the ANS, is orchestrated by the central nervous system. And, like the

SAM, it also involves the amygdala, hippocampus, and adrenal gland, whose

secretions are released into the bloodstream. However, unlike the SAM, the HPA

axis involves a cascade of hormonal processes in which glucocorticoids (GCs,

cortisol in humans) are released into the bloodstream by the adrenal cortex. These

steroid hormones not only target the body, but (unlike adrenaline) also target the

brain. Also unlike adrenaline, whose effects are immediate, the production of GCs

take some time (approximately 25 min to peak levels), and many of its impacts on

the body and brain occur through its effects on changes in gene expression (Gunnar

and Quevedo 2007). As a result, the effects of GCs are slower to develop and they

continue for longer periods of time.

The role of the HPA axis is also more complex than that of the SAM. At basal

levels, the steroids produced by the HPA axis are permissive to the SAM and so

support acute fight/flight responses. However, in response to stressors, the HPA

seems to take over from the SAM by down-regulating its functioning. Moreover,

the effects of GCs depend on the kinds of receptors with which they bind—either

glucocorticoid receptors (GR) or mineralocorticoid receptors (MR). In the body,

GCs only bind with GRs, but the brain has both kinds of receptors. In the brain,

MRs are filled first (since the affinity for GCs is 10 times greater for MRs than



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4 Neurophysiological Developments that underlie Age-related …



GRs), and at basal levels, about 40–60 % are filled. At homeostatic levels, activation of these receptors supports constructive engagement: It enhances synaptic

plasticity, supports better learning in the hippocampus, and provides more glucose

for neurogenesis. Under stress, however, GRs are also filled and they trigger quite

different effects: At high levels, they impair learning, reduce the neural plasticity in

the hippocampus, and inhibit glucose, which reduces cell survival. When levels are

high enough, they also exert negative feedback on the upstream structures, eventually down-regulating the HPA axis—so the system returns to baseline levels.

Several other components of the stress system can also slow or shut down the

functioning of the HPA axis, including the adrenal gland, the hypothalamus, and

other brain regions, such as the hippocampus and the frontal cortex (Lupien et al.

2009).

The amygdala, the medial PFC, and the limbic system. Human neuroendocrine responses to stress are triggered by threat detection systems located in the

amygdala, hippocampus, and ACC in conjunction with the regulatory role of the

orbital/medial PFC, all of which rapidly assess potential danger and activate

autonomic, endocrine, and other physiological regulation systems, including both

the SAM and the HPA axes (Davis and Whalen 2001; Gunnar and Vasquez 2006).

The amygdala plays a central role in rapid detection of potential threats and triggers

adaptive fear responses, by activating the SAM system to mobilize preparation for

fight or flight; it automatically maintains vigilance in conditions of uncertainty,

directs attention to potential danger, and subserves fear conditioning (Davis and

Whalen 2001). Almost two decades ago, LeDoux (1995) summarized evidence that

the amygdala is involved in the processing of negative emotion, receiving input

from the thalamus for quick reactions to threat, and from the hippocampal formation to appraise emotional stimuli. Although evidence was sparse at the time of

LeDoux’s review (and remains so), the amygdala’s importance does not seem to be

limited to the emotion of fear, or even negative emotions in general; research

suggests it plays a more general role in monitoring and learning about the emotional

and motivational significance of environmental events, including both the aversive

and appetitive potential of stimuli (Thayer et al. 2009). Nevertheless, the amygdala

system does seem to be biased toward the processing of negative information,

which likely has been preserved because of its evolutionary advantage. As Thayer

et al. (2012) explain,

Given the evolutionary advantage associated with the assumption of threat, the view that

we and others have proposed is that the “default” response to uncertainty, novelty, and

threat is the sympathoexcitatory preparation for action commonly known as the fight or

flight response (Thayer and Lane, 2009; Herry et al., 2007). This default threat response

may be related to the well-known ‘negativity bias,’ a phenomenon that describes the

tendency to prioritize negative information over positive (Cacioppo et al. 1999). From an

evolutionary perspective this represents a system that errs on the side of caution—when in

doubt prepare for the worst—thus maximizing survival and adaptive responses (LeDoux

1996). (p. 749)



However, this default “on” mode also creates problems for the neuroendocrine

system, since



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continual perception of threat is maladaptive, as it is associated with dysregulation in

hippocampal circuits, endocrine and autonomic output, and cognitive and general health

decline (Chrousos and Kino, 2005; McEwen, 2001; McEwen and Sapolsky, 1995;

Sapolsky, 1996; Seeman et al., 2001). If an organism is to avoid living under a chronic state

of threat, it is imperative to determine if and when threat appraisals are appropriate

depending on the context. The prefrontal cortex and the mPFC in particular, appear to be

important in this process… In safe contexts, ‘fear’ or threat representations in the amygdala

appear to be inhibited by the prefrontal cortex and the vmPFC in particular. (p. 749)



However, the process of tonic inhibition of the amygdala by the vmPFC is not an

automatic one; instead, it exerts its effects via appraisals, essentially getting a

“second opinion” about safety before down-regulating the amygdala. Specifically,

the vmPFC contributes to the consolidation and retrieval of safety context memories, involved in higher-level appraisal processes that operate in certain contexts,

with the guidance of information retrieved from long-term memory (Thayer et al.

2009). As summarized by Thayer et al. (2012), “the vmPFC may inhibit threat

circuits that are by default ‘on’ in a manner that depends on integrating the external

context (environmental threat) with the internal one (perceptions of control over the

threat)… consistent with the idea that the amygdala responds rapidly to biologically

relevant positive or negative stimuli but may be subsequently inhibited if the stimuli

are appraised to be safe or innocuous” (p. 750).

As a central part of the threat detection system, the amygdala serves primarily a

feed-forward effect on the SAM and HPA, up-regulating them in the face of

potential threats. In contrast, the hippocampus, which is also involved in learning

and memory, shows primarily feedback effects, down-regulating the HPA axis

when stress hormones are high. The outputs of both the amygdala and hippocampus

are relayed to subcortical sites (e.g., the bed nucleus of the stria terminalis (BNST)

and the paraventricular nucleus (PVN) of the hypothalamus) where their combined

excitatory and inhibitory effects are integrated before this information is passed on

to the rest of the stress regulatory system (Herman et al. 2005). All the effects of the

limbic system seem to be stressor- and region-specific, in that different regions of

each neural structure are activated by the exact nature of the particular stressor (e.g.,

restraint, novelty, danger; Herman et al. 2005; Thayer and Lane 2009). Both the

hippocampus and the amygdala are densely populated with glucocorticoid and

mineralocorticoid receptors, which make them responsive to the action of the HPA

axis and potential targets to be programmed by elevated levels of stress hormones

(Lupien et al. 2009).

Prefrontal cortex. The PFC includes the brain regions that have received the

most attention in recent research on emotion (especially anxiety and fear, see Etkin

et al. 2011 and LeDoux 1995), stress, regulation, and coping. Of greatest interest to

coping researchers is a region of the medial PFC, called the ventral or rostral ACC,

which is considered to be a foundation for autonomic modulation, attentional

control, and self-regulation (Bell and Deater-Deckard 2007). Although both the

ACC and the amygdala are neural substrates responsible for encoding threat

responses or other affective properties of stimuli, the ACC may be the first part of

the brain to be activated when there is a threat (Compas 2006; Goldin et al. 2009).



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Evidence is accumulating that both the amygdala and the ACC are also involved in

using positive and negative emotions to guide choices and responses in order to

maximize rewards and/or minimize punishments (Beer and Lombardo 2007; Etkin

et al. 2011).

The ACC is especially interesting to researchers studying coping and emotion

regulation because it serves to regulate both cognitive and emotional processing,

while also remaining connected to the ANS. As explained by Bell and

Deater-Deckard (2007),

[t]he ACC is viewed as having two major sections that process cognitive and emotional

information separately, as well as being a source of autonomic nervous system modulation.

The cognitive section has interconnections with the prefrontal cortex, parietal cortex, and

premotor and supplementary motor areas. This portion of the ACC is activated by tasks that

involve choice selection from conflicting information, which includes many target detection

and working memory tasks. The emotion section has interconnections with the orbitofrontal

cortex, amygdala, and hippocampus, among other brain areas. This portion of the ACC is

activated by affect-related tasks” (pp. 412–413).



Although early research suggested that these two subdivisions are antagonistic in

their effects, in that the affective section can be suppressed during cognitive tasks

and the cognitive subdivision can be suppressed during emotion processing, more

recent evidence suggests that the ACC can actually serve as a bridge between

cognition and emotion. It appears to integrate executive cognitive control and the

processing of emotional information, making it a key brain area responsible for “hot

cognition,” that is, for cognitive functioning in situations where emotions are high

(Davidson et al. 2007; Devinsky et al. 1995). In general, the ACC is important for

flexibility of self-regulation and coordination, and has the jobs of watching for

emotionally salient situations and putting regulatory processes into action, including communicating with and being guided by the dorsal medial and lateral PFC.

Overall, there are many regions in and adjacent to the PFC that are critical to

emotion recognition, attention, and cognitive control strategies (Etkin et al. 2011;

Mohanty et al. 2007; Ochsner and Gross 2005, 2007). There is some debate about

the specific PFC regions that are involved in particular regulatory functions (Etkin

et al. 2011; Oschner and Gross 2007), but, in general, regions of the PFC have also

been described as responsible for the representation of goals and the means to

achieve them (Miller and Cohen 2001) and have been linked with affective processing (Davidson et al. 2007). The ACC and other regions of the PFC are dense

with receptors, and communication between the ACC and other PFC regions

continues over a course of time in order to modulate emotional responses, goal

pursuit, response selection, and decision-making. All these brain regions are

reciprocally interconnected; communication is dynamic; and feedback, both positive and negative, is continuous and integrated. The optimal outcome of this

ongoing communication and organization between brain systems is flexible

responding and coordinated regulation of action.

Multiple levels of activation during a stressful encounter. In response to

stress, the ANS, HPA axis, and limbic-amygdala subsystems, in coordination with

the many regions of the PFC, work together to coordinate fundamental threat



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detection and stress responses. As the most primitive line of defense, the PNS can

induce immobilization (or freeze responses) by decelerating the heart. To activate a

second line of defense, the PNS “brake” is released, and the SAM can mobilize

fight and flight responses; high basal activity of the HPA axis also enables swifter

mobilization of the SAM. The rapid SAM system participates in processes that

activate the slower-moving HPA axis. But, once the HPA is activated, the SAM is

subsequently down-regulated. Once dangers are past, the PNS can calm stress

reactions by then completely down-regulating the SAM. The HPA axis can be reset

to homeostatic levels by many systems, including the HPA axis itself, when it

reaches high enough levels of activation.

All of these systems can be activated by exposure to or interactions with psychosocial stressors. Information about the presence of stressors is announced by the

threat detection system, through corticolimbic pathways, including especially the

amygdala, hippocampus, and other structures involved in arousal and vigilance, and

the processing of information from the sensory systems and emotion, behavior,

motivation, and long-term memory. Because many of the effects of the limbic

system are expressed through the hypothalamus, which is part of the HPA axis,

these subsystems are sometimes together referred to as the limbic–HPA axis.

Importantly, when the amygdala–limbic system is activated, threat responses are

taken over by “automatic” systems, as these responses are much faster than cortically mediated control mechanisms. So the regulatory mechanisms of the PFC are

temporarily “disabled.” As Thayer and Lane (2009) go on to explain, “under

conditions of uncertainty and threat critical areas of the PFC become hypoactive.

This hypoactive state is associated with disinhibition of sympathoexcitatory circuits

that are essential for energy mobilization” (p. 83). Although these complex systems

clearly serve survival functions (because they support both the detection of threats

and action readiness), a great deal of research documents the serious wear-and-tear

all these systems (especially the SAM, HPA axis, and amygdala) can generate when

they are chronically overactivated (e.g., McEwen 2004).

At the same time, researchers point out that it can also create problems if they are

chronically underactive (Phillips et al. 2013): The HPA axis and PNS also serve

important homeostatic functions at basal levels, functions that support alertness,

constructive engagement, and learning. All of these important processes can be

impaired if such systems are under-responsive. Hence, the optimal functioning of

stress reactivity systems includes high and responsive basal levels to support productive social and goal-directed interactions, accompanied by robust,

well-orchestrated activations when stressors are encountered, followed by smooth

and complete recovery that restores the systems to homeostatic functioning as soon

as the stressor has passed.



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4.1.2



4 Neurophysiological Developments that underlie Age-related …



Stress Reactivity and Regulation as Complex Dynamic

Systems



Although much of what is known about the neurophysiological systems that

underlie stress reactivity and coping is theoretical rather than based on a robust

body of empirical research, nevertheless, in general, developmental neuroscientists

and neuroscientific models view these processes as hierarchical and nonlinear

dynamic systems involving a complex interplay of anatomical areas that subserve

stress reactivity, threat detection, and the regulation of attention, emotion, and

cognition under stress (Dennis 2010), as well as relying on a number of neuromodulators (e.g., serotonin and dopamine), genes, and parts of the central and

peripheral nervous systems (Bell and Deater-Deckard 2007). The complexity of

these biological systems is apparent in the multiple ways that parts of the brain

communicate and respond across diverse regions, and how they mutually regulate

each other. All of this adds up to a complex and dynamic interacting and emergent

system with multiple set points and feedback systems that function to coordinate

external and internal conditions. These systems are “interacting and competing,

each with its own function and regulatory role” (Lewis and Todd 2007, p. 413),

making the organism a “complex set of reverberating circuits of sub-systems

working together in a coordinated fashion…this complex system, as it moves

through time on numerous time-scales, requires various feedback and feedforward

circuits for efficient functioning…[it] is not orchestrated from a central command

center” (Thayer and Lane 2000, p. 203).

Integrated stress reactivity systems. In an attempt to describe the neurobiological organization of the stress system responsive to psychological stressors,

Gunnar and Quevedo (2007) distinguish three interconnected levels: First, “[t]he

cortico-limbic level of organization involves the anterior cingulate (ACC) and

orbital frontal cortex (OFC), which relay information to subcortical structures

involved in the stress response. The ACC and OFC are reciprocally interconnected

with each other and with the amygdala, which has connections with the hippocampus and bed nucleus of the stria terminalis (BNST).”

Second, “[t]he hypothalamic–brain stem level of organization involves the

hippocampus and brain stem structures such as the locus coeruleus (LC), which

releases norepinephrine (NE) to brain areas involved in alerting. The BNST provides pathways into the paraventricular nucleus (PVN) of the hypothalamus, which

produces corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP),

while the hippocampus and regions in the medial frontal cortex (e.g., ACC)

maintain feedback control of the PVN.” And third, at the “the neural-to-adrenal

level of analysis, nuclei in the lateral hypothalamus activate highly interconnected

nuclei in the brain stem, including the parabrachial nuclei, that regulate the sympathetic (NE and epinephrine, Epi) and parasympathetic (acetylcholine, Ach) nervous systems via pathways traveling through the spinal cord to preganglionic nuclei

or to target organs (e.g., the adrenal medulla). The production of CRH and AVP by



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the PVN regulates activity of the hypothalamic–pituitary–adrenocortical

(HPA) axis and the production of glucocorticoids (GCs)” (p. 151).

Neurovisceral integration model. An even more holistic view of this complex

system is presented in the “neurovisceral integration model,” which attempts to

integrate the functioning of these neuroendocrine circuits with the neurophysiological systems that underlie parasympathetic and sympathetic responding, and with

brain regions that participate in the regulation of cognition, emotion, and attention

(Bell and Deater-Deckard 2007; Thayer et al. 2009; Thayer and Lane 2002, 2009).

These researchers have proposed that all these subsystems, which up until now have

largely been studied in relative isolation from each other, can be seen as overlapping parts of a single psychophysiological system responsible for self-regulation

under a range of differing internal and external conditions.

Together, they can usefully be considered “a flexible network of neural structures that can be differentially recruited in response to challenges [that] lead to

‘emergent’ functional networks that are context specific” (Thayer and Lane 2009,

p. 84). Self-regulation may comprise a unitary holistic system with multiple levels

or multiple states, making it hierarchical and dynamic, and—importantly—endowing it with the potential to be exquisitely responsive to biological and environmental conditions (Lamm and Lewis 2010). From this perspective, threat

detection, stress reactivity, emotional regulation, executive attention, cognitive

control, and recovery from stress—and coping—are all parts of a single integrated

and organized neurophysiological system; these parts can be (re)assembled into a

wide variety of functional units in response to particular patterns of internal and

external demands.

This seems to be the “super-system” that underlies coping. According to Thayer

et al. (2012), its function is to provide a neurophysiological platform that supports

adaptations to environmental challenges. As they explain,

adaptations to environmental challenges are shaped by influences from many sources:

physiological, behavioral, affective, cognitive, social, and environmental. Despite this

diversity, or perhaps because of it, a hallmark of successful adaptation is flexibility in the

face of changing physiological and environmental demands. We have proposed that a core

set of neural structures provides an organism with the ability to integrate signals from inside

and outside the body and adaptively regulate cognition, perception, action, and physiology.

This system functions both to continuously assess the environment for signs of threat and

safety and to prepare the organism for appropriate action. In addition, it monitors the match

between the external environment and the body’s internal homeostatic processes in order to

generate motivational drive states and adaptive physiological adjustments… This system

essentially operates as a “super-system” that integrates the activity in perceptual, motor,

interoceptive, and memory systems into gestalt representations of situations and likely

adaptive responses. (pp. 747–748)



From this perspective, the brain areas identified as important for each aspect of

coping are all subsystems of the same neurovisceral super-system. They have

complex interconnections, and they organize and activate each other in very specific

ways that depend on the initial conditions of the organism, the level and type of

emotion, the developmental level of the person, the type of challenge or threat, the

other resources available, and a history of responding to similar or related events.



4 Neurophysiological Developments that underlie Age-related …



74



Central to this super-system is the medial prefrontal cortex (mPFC), which, as

explained by Thayer et al. (2012),

[serves] a particularly important part of the “core integration” system because it plays a

critical role in the representation of both internal and external context in the brain and the

use of both kinds of information to regulate behavior and peripheral physiology. Its role in

cognition is centered around the construction of context, including autobiographical

memory retrieval (McDermott et al., 2009) and expectations about future outcomes

(Schoenbaum et al., 2009; Summerfield et al., 2006). It is also considered to be a key area

for the representation of economic value (Hare et al., 2010; McClure et al., 2004;

Plassmann et al., 2008), the sense of the self (Kelley et al., 2002; Northoff et al., 2006), and

emotional appraisal (Urry et al., 2006; Wager et al., 2008c). Finally, it also plays a critical

role in the regulation of both behavioral and physiological responses, including regulation

of “fear responses” (Delgado et al., 2008; Milad et al., 2007; Schiller et al., 2008), heart-rate

changes related to social threat (Wager et al., 2009c), and a variety of other peripheral

responses to stressors (Lane and Wager, 2009) through connectivity with the brainstem

(Keay and Bandler, 2001; Saper, 2002; Wager et al., 2008a, 2009b).



In other words, in many ways, the mPFC serves as the initial clearinghouse for

the detection of threat and as a hub for the integration of information from the

multiple sources needed to support adaptive responding and coping. These include

goal-directed “cognitive” information, emotional and social information, motivational information (rewards and punishments), and autonomic and visceral

responses. As a result, Thayer et al. (2012) describe the integrated neurovisceral

system as a “MPFC-guided ‘core integration’ system” (p. 748) that subserves

adaptations to environmental challenges.



4.2



The Assessment of Neurophysiological Structure

and Function



Researchers have developed increasingly sophisticated approaches to measuring the

physiological underpinnings of stress responses, as well as coping and regulatory

processes. These approaches involve assessing activity within one or more of three

core brain systems: the brainstem, limbic, and cortical systems. The methods

employed most frequently include measuring respiratory sinus arrhythmia (RSA or

vagal tone), assessing brain activity in the form of event-related potential (ERP),

assaying neuroendocrine markers of stress via cortisol or alpha amylase

(sAA) presence in saliva, and using magnetic resonance imaging (MRI) or functional MRI (fMRI). All of these methods are now being used to assess the functioning of neurophysiology related to emotion, cognition, threat detection, threat

appraisal, and coping, and to understand how this functioning might explain different behavioral patterns or problems that arise when individuals are responding to

stressful events or challenging tasks. These methods of assessing brain or other

physiological activity are also making their way into the examination of development; a number of studies have now been conducted to compare children of different ages or to compare children to adolescents and adolescents to adults.



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1 Neuroanatomical Systems involved in Stress Reactivity, Regulation, and Coping

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