The Neurobiology of Extreme Stress Broken Down Barney- Style

Transcription

1 The Neurobiology of Extreme Stress Broken Down Barney- Style ARIZONA COALITION FOR MILITARY FAMILIES 6 th Annual Symposium April 23, 2015 William P. Nash, M.D. CAPT, MC, USN (Re.red) william.nash@opstress.net 1

2 Barney Style in the Marine Corps 2

3 Let s Play Category: Clue: Correct Response: 3

4 Stress Injury: A Better Explanation Normal Stress You choose it (largely) Temporary Reversible Func>oning is maintained Integrity is maintained Stress Injury It happens to you (largely) Leaves a scar Cannot be undone Func>oning is diminished Integrity is diminished Nash, W.P. (2007). Combat Stress Adapta.ons and Injuries. In C.R. Figley & W.P. Nash (Eds.). Combat Stress Injury: Theory Research and Management. New York: Routledge. 4

5 USMC USN Stress Continuum MCRP 6-11C/NTTP 1-15M, Combat and Opera.onal Stress Control, 2010, p

6 Predictors of PTSD Trajectories in Deployed Marines Latent classes of PTS symptom trajectories, by growth mixture modeling, in (N = 867) infantry Marines from a single unit deployed to Afghanistan from Camp Pendleton PTSD SEVERITY IN CAPS UNITS Low- Stable Sx Pre- Exis.ng PTSD New- Onset PTSD PRE- DEPLOYMENT 1 MONTH POST 3 MONTHS POST 13% 8% 79% 8 MONTHS POST Predictors of membership in New- Onset trajectory* Childhood trauma Prior lifespan trauma Combat experiences Peritraumatic dissociation W p <.001 *With respect to the Low- Stable trajectory Nash WP, et al. J Abnorm Psychol Baker DG, Nash WP, Litz BT, et al. Preventing Chronic Disease. 2012; 9 6

7 Let s Play Category: Clue: Correct Response: 7

8 Triune Brain: Layers of Top- Down Control MacLean, P.D. (1990). The Triune Brain in Evolu?on. New York: Plenum Press. 8

9 Six Brain/CNS Systems Involved in Stress 1 2 Sympathe>c nervous system (SNS) Parasympathe>c nervous system (PNS) BODY Spinal cord Bodily ac.va.on ( Fight or Flight ) Bodily relaxa.on ( Feed or Breed ) 3 Nucleus accumbens (NA) 4 Amygdala 5 Hippocampus 6 Prefrontal cortex (PFC) HEART HEAD Brain stem Temporal lobe Frontal lobe Mo.va.on, pleasure, focus, agen.on, addic.on Emo.onal experience and memory Meaning- making, contextual memory, self- control

10 Two Opposing Sides of the Autonomic Nervous System Sympathetic Parasympathetic FIGHT OR FLIGHT FEED OR BREED

11 Do extremely stressful experiences tend to disrupt the balance between sympathe.c and parasympathe.c nervous systems? If so, which tends to be overac.ve? Sympathe.c? or Parasympathe.c? Why is the balance lost?

12 Nucleus Accumbens (NA): Center for all Motivation and Pleasure Functional MRI (fmri) scan showing the Nucleus Accumbens in the brain of someone listening to their favorite music Internal reward center Uses dopamine as its neurotransmitter Dopamine activity in NA associated with: Pleasure Motivation Attention Focus Excitement = dopamine rush (not adrenaline)

13 Two Major Ways Stress Affects the Nucleus Accumbens Addic.ons Sensi.ze the NA to seek a par>cular source of pleasure May be a substance or a behavior Results in persistent decrease in NA dopamine ac>vity except when engaging in addic.on Withdrawal Large dip in dopamine ac.vity in NA when addic.ve substance or behavior is withdrawn Dysphoria, agita.on (increased SNS ac.vity) Craving 13

14 Amygdala: Emotion Generator About the size and shape of an almond Attaches emotions (of all kinds) to experiences and memories Fear and anger Warmth and compassion Emotional threat detector Never forgets Amygdala

15 Fear Conditioning: Traditional Explanation for PTSD Fear conditioning is a form of rapid emotional learning in the amygdala Once the amygdala learns a situation is a threat, it will react every time in a similar situation Amygdala always activates sympathetic nervous system and fight or flight response To extinguish fear conditioning, hippocampus and prefrontal cortex must be engaged

16 Hippocampus: Meaning Maker Hippocampus Shaped like an upsidedown seahorse Necessary for memory storage & retrieval Makes connections between current experiences and memories based on context and meaning Very plastic, easily changes its mind

17 Pre- Frontal Cortex (PFC): Internal Brake and Steering Wheel Master switchboard for self-control Exerts authority over: Emotions Thoughts Memories Impulses Pain Autonomic nervous system 17

18 How Does Extreme Stress Affect Hippocampus and Prefrontal Cortex? Experiences can t be organized and stored in long-term memory if they don t make sense PFC and hippocampus highly dependent on social meaning (values, ideals, attachments) Neurons in PFC and hippocampus that are most sensitive to the environment are also must vulnerable to death from overstimulation Excitotoxicity Glutamate neurons using NMDA receptors also make retina and inner ear vulnerable to overstimulation

19 Stress Is Not the Only Cause of Excitotoxic Neuron Death in Hippocampus and PFC Stress The exact same mechanism accounts for noise-induced hearing loss and blindness due to intense light exposure Stroke Blast Wounds Too much electrical signal Ca++ Influx through NMDA receptors Infection But glutamate neurons in hippocampus & PFC can regrow!

20 Brain Systems Under Normal Stress Prefrontal Cortex & Hippocampus Amygdala Dopamine, Nucleus accumbens Norepinephrine, Adrenaline, Sympathetic N.S.

21 Brain Systems Under Extreme Stress Crap! Lost it again! What s Changed? Amygdala is cracking its whip harder & faster Hippocampus & prefrontal cortex have lost control Adrenaline and dopamine are on overdrive SNS is maxed out

22 CRF, Cortisol, and BDNF: Beyond Barney Cor>cotropin Releasing Factor (CRF) is the master stress modulator ( on switch for stress) in the brain A hormone released in the hypothalamus triggering release of cor.costeroids like cor>sol from adrenal cortex A neurotransmiver used by a network of neurons in the brain Cor>sol is the major off switch for stress Both CRF and cor.sol have biphasic ac>vity in the brain: At low- moderate levels: improved performance, learning, and well- being At high levels: degraded performance, learning, and well- being Cor.sol interacts with brain- derived neurotrophic factor (BDNF) to s.mulate growth of new dendrites, synapses, and en.re neurons, but in different brain systems depending on stress level (e.g., Sapolsky, 2003; Bennet et al., 2014) 22

23 Differential CRF, Cortisol, and BDNF Effects at Low Moderate vs. Extreme Stress Brain systems Low Moderate Stress Extreme Stress PFC & Hippocampus Amygdala Nucleus accumbens in density of dendrites and synapses in numbers of neurons in density of dendrites and synapses in numbers of neurons in dopamine release in well- being in mo.va.on, problem- solving (ac.ve coping) in density of dendrites and synapses in numbers of neurons in density of dendrites and synapses in numbers of neurons in dopamine release in well- being in mo.va.on, problem- solving (avoidant coping) (Bennet et al., 2014; Davidson et al., 2012; de Quervain et al., 2009; Lemos et al., 2012; McEwen, 2013; Sapolsky, 2003) 23

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