Graphic of the Defense Cascade – HOMI

Homi v5

H-O-M-I: Happy-Orient-Mobilise-Immobilise (after Porges)

I have been playing with a new graph explaining the defence cascade in response to the perception of threat. The graph shows phases of how we respond to threat and a new mnemonic HOMI.

The Happy phase is added to emphasise the new vagus is firing at its maximum when we are playing. I have noticed students get confused when I merge happiness and orienting in my explanations. Hopefully this makes it a bit easier.

As the ‘vagal brake’ comes off due to the perception of threat, more primitive action patterns emerge. Initially in the orienting phase these changes are mediated by activity in the Ventral Vagal Complex (‘VVC’ – cranial nerves V, VII, IX, X, XI ). Simple action patterns emerge that influence head turning, facial expression, focus, breathing and heart rate.






Thoughts on the Defense Cascade, Freezing and Arousal

Defense Cascade

Kozlowska et al 2015 have written a very impressive review of trauma physiology. This post covers my attempt to make sense of the way they describe responses to threat; ‘the defense cascade’.

The defense cascade is described as a sequence, that feels a little rigid. The authors acknowledge that prior learning means that threat can trigger any one of a number of responses. The venn diagram attempts to show the defense cascade in a non hierarchical way.

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Freeze is defined by Kozlowska et al in a very particular way as ‘flight-or-fight on hold’ or ‘attentive immobility’ or ‘despite being immobilised, the rat remains alert’. They reserve the term ‘tonic immobility’ for last ditch, passive responses to threat. In the past I have often described immobility as dissociation, and, confusingly, freeze (freeze as tonic immobility is fairly common see Levine, van der Kolk and Porges).

The images below on ‘Threat Causes Arousal’ show different types of response that I put under the umbrella term Orientation. I do not feel that ‘freeze’, ‘social engagement’ or ‘tend and befriend’ completely describe the range of responses that are possible as we become aroused. Orientation covers the responses before we go into mobilisation – a full sympathetic response of fight-or-flight.

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Polyvagal Theory

Kozlowska et al 2015 utilise polyvagal theory in their descriptions of the defense cascade, though for me they underplay the importance of social engagement. The images below on polyvagal theory are still my preferred simple overview of the human responses to threat. Some direct Porges quotes are below:

‘Sequence of response strategies: (1) removal of VVC (ventral vagal complex) then, (2) increase in sympathetic tone, and (3) a surge in DVC (dorsal vagal complex DMN) tone.’ Porges (2011 p165).

‘In contrast, defensive behaviors could be categorized into two domains: one related to mobilization including fight and flight behaviors and the other related to immobilization and death feigning that might be associated with dissociative psychological states. Within this dichotomy of defensive strategies, freezing behavior that requires increased muscle tension in the absence of movement, such as stalking or vigilance behaviors, is categorized within mobilization. In contrast, immobilization is associated with a decrease in muscle tension and often with fainting and other features of decreased metabolic activity.’ Porges (2011 p267).

‘When the environment is appraised as being safe, the defensive limbic structures are inhibited enabling social engagement and calm visceral states to emerge. In contrast, some individuals experience a mismatch and the nervous system appraises the environment as being dangerous, even when it is safe. This mismatch results in physiological states that support fight, flight, or freeze behaviors, but not social engagement behaviours.’ Porges (2011 p273).

Bold added, in the second quote from Porges the text supports the ‘freeze’ concept of Kozlowska et al. However in the third quote he also uses ‘freeze’ as something different from social engagement.

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You can download as slide show here: Defense Cascade Steve Haines 2015-11

Kozlowska K, Walker P, McLean L, and Carrive P (2015) Fear and the Defense Cascade: Clinical Implications and Management. Harv Rev Psychiatry. 2015 Jul; 23(4): 263–287.

Porges, S. (2011) The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication, and Self-Regulation. New York: Norton

Taylor SE, Klein LC, Lewis BP, Gruenewald TL, Gurung RA, Updegraff JA (2000) Biobehavioral responses to stress in females: tend-and-befriend, not fight-or-flight. Psychol Rev. 2000 Jul;107(3):411-29.

Want more?

Check for a video with great examples of tonic immobility, freeze and mobilisation in a mouse surviving a cat attack.

Even More?

Buy ‘Trauma Is Really Strange’, a non-scary comic book about trauma by Steve Haines, art by Sophie Standing:

Mouse Escapes After Immobilising: Great Demo of Defense Cascade

Immobility in the Defense Cascade

The above video captures some essential elements of hardwired trauma responses. Notice how stiff the mouse is at the start of the video @0.00 and 0.09 mins – a dissociative, immobilised state and a perfect example of ‘tonic immobility’. Later @0.29 it is in the ‘freeze’ state of  ‘flight-or-fight on hold’  where the body is still but there is quick breathing and orientation to the environment. Finally, @0.51 we see it go into ‘flight-or-fight’ and attack the cat. These are all stages of the ‘defense cascade’ outlined by Kozlowska et al 2015.

The mouse survived.

Two passages from Peters Levine’s excellent book ‘In An Unspoken Voice’ help us understand why a mouse would attack a cat – not a rational response:

As They Go In, So They Come Out: The Rage Connection

‘Similarly, when a well-fed household cat catches a mouse, the latter, restrained by the cat’s paws, stops moving and becomes limp. Without resistance from the mouse, the cat becomes bored and will sometimes gently bat the inert animal, seemingly trying to revive it and restart the game anew (not unlike Jimmy Stewart slapping his swooning heroine to bring her out of her faint). With each reawakening, chasing and reactivated terror, the mouse goes deeper and longer into immobility. When it does eventually revive, it frequently darts away so quickly (and unpredictably) that it may even startle the cat. This sudden, non-directed burst of energy could just as easily cause it to run at the cat, as well as away from it. I have even seen a mouse ferociously attack the nose of an astounded cat. Such is the nature of exit from immobility, where induction has been repetitive and accompanied by fear and rage. Humans, in addition, reterrorize themselves out of their (misplaced) fear of their own intense sensations and emotions.

This is similar to what may happen when catatonic psychiatric patients come out of their immobility. They are often extremely agitated and may attack the staff. I once had the opportunity to work with a patient who had been in a catatonic state for two or three years. After carefully sitting by his side (getting closer, over the period of several days), I spoke to him softly about the shaking and trembling that I observed with people and animals when they come out of shock. I had also talked with the chief psychiatrist, and he agreed that they would not give him an injection of thorazine (or straitjacket him) if he came to in an agitated state, unless he was clearly dangerous to himself or others. Two weeks later l got a call from the psychiatrist. The man had begun to shake and tremble, started to cry and was released to a transitional living situation six months later.

To review, fear both greatly enhances and extends immobility and also makes the process of exiting immobility fearful and potentially violent. An individual who is highly terrified upon entering the immobility state is likely to move out of it in a similar manner. “As they go in, so they come out” was an expression that Army M.A.S.H. medics used when describing the reactions of their war-wounded patients. lf a soldier goes into surgery terrifed, and needing to be held down, he or she will likely come our of anesthesia in a state of frantic and possibly violent disorientation.’

Levine 2010 pp61-62 (Italics from original, bold added.)

The Fear of Exiting Immobility

‘In the wild, when a prey animal has succumbed to the immobility response, it remains motionless for a time. Then, just as easily as it stopped moving, it twitches, reorients and scampers off. But if the predator has remained and sees its prey returning to life, the story has a very different ending. As the prey comes back to life and sees the predator standing ready for a second (and this time lethal) attack, it either defaults to all-out rage and counterattacks, or it attempts to run away in frantic non-directed flight. This reaction is wild and “mindless”. As I mentioned in Chapter 4, I once saw a mouse counterattack a cat that had been batting it about with its paws (bringing the mouse out of its stupor), and then scurry away leaving the cat dazed, like Tom-cat in a Tom and Jerry cartoon. Just as the immobilized animal (in the presence of the predator) comes out ready for violent counterattack, so too does a traumatized person abruptly swing from paralysis and shutdown to hyper-agitation and rage. Fear of this rage and the associated hyper-intense sensations prevents a tolerable exit from immobility unless there is education, preparation, titration and guidance.’

Levine 2010 p88 (Bold added.)

A huge thanks to Renee Hella from Body Intelligence Vancouver. She shot and uploaded the video, she thinks the cat was distracted by the camera. It is also a stout cat.


Kozlowska K, Walker P, McLean L, and Carrive P (2015) Fear and the Defense Cascade: Clinical Implications and Management. Harv Rev Psychiatry. 2015 Jul; 23(4): 263–287. Accessed 2015-10-28

Levine P. (2010) In an Unspoken Voice: How the Body Releases Trauma and Restores Goodness. Berkeley, CA: North Atlantic Books.