1. Evolutionary Threat Assessment Systems Theory (ETAS Theory)
Chapter 14
Evolutionary Threat Assessment Systems Theory (ETAS Theory)

2. ETAS
Areas of the brain evolved overtime to assess potential threats of harm
Brain stem, basal ganglia, limbic system, & prefrontal cortex (PFC)
Due to evolutionary origins these 4 areas process info about threats differently
Operates on 3 systems that assess threat…
1. Instinctual processing – oldest; brain stem & basal ganglia
2. Emotional/affective processing – limbic system & structures associated
3. Rational/cognitive processing – PFC
Areas (oldest – newest) brain stem, basal ganglia, limbic system, PFC
ETAS = systems in the brain which have evolved over course of our evolutionary history designed to assess degree of threat out there in the world

3. ETAS premise…
Threat assessments potentially bring about psychiatric sx
Psychiatric sx are the product of threat assessment systems which evolved for self-protection
Psych sx represent evolutionary adaptations that were once essential for survival

4. Original ETAS Model (Flannelly, 2007) –
Theoretic article – proposed mechanisms underlying psych disorders involve neural circuits connecting the…
Basal ganglia
Limbic system
Prefrontal cortex (PFC)
Each area receives separate sensory input – they make threat assessments influenced by past experience
Beliefs directly effect PFC (which evaluates threat assessments of basal ganglia & limbic system)

5. Original ETAS model
Each area receives sensory input
They make threat assessments based off previous experience
Belief directly affects prefrontal cortex
Prefrontal cortex evaluates threat assessments of basal ganglia & limbic system

6. Original ETAS Model
This theoretical model does not include degree of involvement of brain regions
Does not include the brain stem
But implies multiple brain systems are needed to assess threat &
Psychiatric sx represent system’s reactions to potential threats of harm

7. ETAS Theory after 2007
Since the 2007 article – more published theoretical articles supporting basal ganglia, limbic system, PFC, and brain stem are involved in threat assessment
Authors discuss different theories but what distinguishes ETAS from other theoretical models?
*explains how beliefs influence psych sx by influencing brain systems that make threat assessments
So, beliefs affect psychiatric sx through brain systems

8. Updated model of ETAS
Illustrates basic interconnections among the 4 brain regions
Prefrontal cortex
Limbic system
Basal ganglia
This is a more simplified model – eliminates sources of input used by different brain regions
Brain stem
Figure Schematic general model of ETAS, showing the theoretical involvement of four key brain areas in psychiatric symptoms

9. Flannelly’s Literature Review
Lit review of different brain regions in psychiatric disorders that are thought to be the product of evolutionary adaptations
(Here’s a pic of a few areas that’ll come up during discussion)

10. Findings Psychiatric disorder Prefrontal cortex Limbic system
Table 14.1 – Involvement of different brain regions in psychiatric disorders that are thought to be the product of evolutionary adaptations
Psychiatric disorder
Prefrontal cortex
Limbic system
Basal ganglia
Brain stem
Panic attack √
Social anxiety
Major depression
Paranoid ideation
General anxiety
Animal phobia
Obsession-compulsion

11. Results All 4 regions involved in panic, social anxiety, & MDD
PFC strongly implicated in all disorders
Specifically the ventromedial area of the PFC (vmPFC)
social anxiety & depression  brain stem weak involvement
basal ganglia strong involvement
panic disorder  brain stem strong involvement
basal ganglia weak involvement
Areas of limbic system associated w/social anxiety & MDD
Amygdala
Anterior cingulate cortex (ACC)
Insula

12. GAD – strong evidence for PFC & limbic system
Paranoid ideation – strong evidence for PFC, limbic system, & basal ganglia involvement
GAD – strong evidence for PFC & limbic system
Specifically vmPFC & amygdala
Small animal phobia (snakes and spiders)
PFC & limbic system strongly implicated
NO research suggests basal ganglia or brain stem involvement
These 2 structures evolved before the fear of small animals
So it’s a relatively new adaptation bc it evolved long after evolution of these structures

13. OCD Limbic system strongly implicated in all disorders except OCD
The amygdala is implicated in every disorder where limbic system is involved – except OCD
Amygdala is thought to be primary anxiety/fear area in humans
OCD is an anxiety disorder so it’s weird the amygdala has no implication
Anxious thoughts and repetitive behaviors exhibited in OCD indicate problems w/basal ganglia – controls repetitive ritualized behaviors in animals (fixed-action patterns)
***Basal ganglia evolved long before cognition – so anxious thoughts in OCD could be associated w/instinctive behaviors serving as survival functions or self-protection
Weak involvement of limbic system in OCD

14. vmPFC in Deductive Reasoning & Influence of Beliefs
The prefrontal cortex is involved in inductive logic/reasoning and deductive logic/reasoning
Inductive reasoning – dorsolateral PFC (dlPFC)
Deductive reasoning – ventromedial PFC (vmPFC) – 2 brain systems involved
Uses language & abstract reasoning
2. Doesn’t rely on language; not strictly logical; deductions in vmPFC can be influenced by beliefs
vmPFC assigns probabilities to a stimulus when assessing if it’s a threat
Probabilistic decision making is influenced by beliefs about world

15. Threat, Safety, & the vmPFC
Paul Gilbert
Human brain contains threat system and safety system
Safety system evolved in context of social relationships
Relationships w/supportive helpful ppl promote sense of safety
Sense of safety alters processing of potential threats – one can feel relatively safe even in the presence of threat stimuli
Gilbert’s safety system is based on John Bowlby’s Attachment theory
Attachment relationships can reduce sense of threat
vmPFC – responsive to safety cues and involved in attachment and social emotion
Just as vmPFC assigns probabilities to a threat, it may also assign probabilities about safety
A sense of safety alters the processing of potential threats – one can feel safe even in presence of threatening stimuli
Arnold & Folkman – stress buffering effect refers to the hypothesis that the perceived availability of social resources reduces one’s assessment of the severity of threats posed by adverse events in one’s life

16. Little evidence of association between “sense of safety” & psychiatric disorders but…
Substantial evidence that (+) social relationships have beneficial association with mental health – many studies confirm the notion, “stress buffering effect”, of supportive social relationships on mental health
Psychological characteristics like self-esteem and self-efficacy can also act as a buffer against threat-related anxiety
Flannelly suspects psych symptomology (especially anxiety), influences effects of religious beliefs & other beliefs about (+) emotion
***ETAS plays a role in controlling (+) and (-) emotions associated w/psychiatric sx

17. Role of vmPFC in Threat Assessment
Plays critical role in threat assessment – independently assesses safety & threats
vmPFC can override other subcortical areas of the brain to inhibit amygdala activity  reducing fear (& psych sx related to fear)
Belief processing
To assess threat  vmPFC makes assumptions based on belief  beliefs about the world interact to moderate threat assessments  affects psychiatric sx

18. Roles of Other PFC Regions in Threat Assessment
Orbitofrontal region (OFC)
There is limited evidence – OFC may be involved in threat assessment & regulation of amygdala
Involved in processing beliefs that influence amygdala activity
Associated w/optimism reducing anxiety
Remember: role of vmPFC in threat assessment is that it can inhibit amygdala activity  reduce fear
OFC may serve function similar to vmPFC in threat assessment

19. Dorsomedial PFC (dmPFC)
Human dmPFC enhances amygdala activity through an “aversive amplification circuit”
Circuit includes
Amygdala
dmPFC
Anterior cingulate cortex (ACC)
ACC is involved in cognitive assessments of threat
Another PFC region involved in threat assessment = dmPFC
No evidence of belief processing in the dorsomedial prefrontal cortex
The circuit is associated with elevated threat processing – enhances fear by priming amygdala to be more sensitive to potential threats

20. Evolutionary Threat Assessment Systems Functioning
(mostly a recap)
Brain stem, basal ganglia, limbic system, & PFC thought to be involved in threat assessments which underlie psych sx
Structures in each region assess threats as part of their function
Brain stem, basal ganglia, & limbic structures  automatic processing of threats; outside of awareness
ACC & insula of limbic system  conscious processing of threats
Evolved at different points in time
3 systems – brain stem & basal ganglia = instinctive level
limbic structures = emotional
PFC = cognitive level

21. Subcortical structures, mostly amygdala, make automatic assessments about whether something is a potential harm or not
W/unpredictability – amygdala treats even non-threatening things/objects as potential threats (better safe than sorry principle)
Then PFC integrates info from subcortical structures and makes its own threat assessments based on cognition
Ventromedial PFC can override amygdala assessments by inhibiting its activity  reduction in fear
Dorsomedial PFC including the “aversive amplification circuit” increases amygdala activity  more sensitive to threats  increasing fear

22. Other things vmPFC takes into account
When vmPFC makes threat assessments it takes beliefs into account when assigning a probability that a stimulus poses a threat
Other things vmPFC takes into account
Personal safety
Social support, situations, & beliefs that provide sense of safety
If vmPFC decides there’s no threat  decreased amygdala activity  decreases anxiety & related sx
Since vmPFC decisions are probabilistic, it may modulate amygdala activity in terms of degree of threat posed  modulates anxiety and related sx
Modulate – like to modify or control for

23. The vmPFC is like a gating system – sets a threshold for what is/is not a threat of harm
vmPFC appears to raise threshold of what constitutes a threat given its ability to reduce amygdala activity
dmPFC may lower threshold of what constitutes a threat by priming amygdala to be more sensitive to potential threats

24. Chapter Highlights/Summary
Researchers & clinicians agree that psychiatric sx in patients & the general public are the product of neural systems that evolved to provide self-protection through assessing the threat of harm posed by objects and situations
ETAS Theory explains how neural systems involve certain brain areas implicated in psychiatric disorders – explains how systems work and how they cause psych sx
According to this theory, subcortical structures (brain stem, basal ganglia, limbic system) unconsciously assess potential threats and relay this info to the PFC
vmPFC plays critical role in threat assessment bc its involved in deductive reasoning & processing beliefs; deductive decisions are influenced by beliefs about world; it is particularly sensitive to safety cues
vmPFC makes its own assessment of degree of threat of harm, taking safety, beliefs, & other info into account

25. continued…
If vmPFC decides stimulus does not pose a threat it decreases the activity of the amygdala, which decreases anxiety & related symptoms
Since vmPFC decisions are probabilistic it may modulate amygdala activity in terms of degree of threat posed by the stimulus, therefore it could modulate anxiety & related symptoms
vmPFC acts as gating system setting a threshold for what is/isn’t threat of harm
dmPFC, & possibly other areas of the PFC, may process beliefs capable of increasing anxiety and other psychiatric symptoms by increasing amygdala activity

26. The End 