Extinction is the Path to the Light Side of the Force

A Learning Theory Perspective on Pain-related Fear in Chronic Pain

Every saga has a sequel – well in the previous blog post on learning and pain-related fear in chronic pain, I explained how pain-related fear can be acquired through associative learning, that is, the systematic pairing of a neutral movement (conditioned stimulus = CS) with a painful stimulus (unconditioned stimulus = US). I introduced a voluntary movement conditioning paradigm using joystick movements as CSs and a painful shock as the US as an experimental tool to study pain-related fear in the lab as this would best mimic the prototypical fear of painful movement that has frequently been described by patients with musculoskeletal pain. Finally, I argued that pain unpredictability evokes another form of pain-related fear characterized by more general distress, worry, and chronic apprehension that is associated with increased pain intensity. In this blog post, I will focus on how we can reduce pain-related fear once it has been acquired.

Fear extinction

If fear (acquisition) is the path to the dark side, then fear extinction is the path to the light side of the Force. Following a learning theory perspective, acquired fear of movement can be reduced by graded in vivo exposure therapy, or what is known as the clinical analogue of a Pavlovian extinction procedure. This cognitive-behavioral treatment entails gradual exposure to the feared movement/activity, usually following a fear hierarchy, until fear is reduced and daily functioning can be resumed. Initial evidence in patients with chronic back pain, complex regional pain syndrome, and posttraumatic neck pain suggests that exposure therapy is  effective in mitigating fear levels, functional disability, and pain report. Despite the apparent success of exposure in the clinic, fundamental research about its underlying mechanisms lags behind. Another question that remains to be answered is how to treat patients who do not have clear triggers for increased pain episodes, those demonstrating generalized pain-related fear.

An experiment using a voluntary movement conditioning paradigm

In our most recent study with the joystick paradigm (Meulders & Vlaeyen, 2012), we investigated extinction of both types of pain-related fear, i.e., fear of movement (induced by predictable pain) and more generalized pain-related fear (induced by unpredictable pain). All groups received acquisition training in both the predictable and the unpredictable context. This means that in the predictable context, one movement direction predicted painful shock to the hand (e.g., moving to the left was followed by shock (CS+) and moving to the right was never followed by shock (CS-)). In the unpredictable context, painful stimuli were delivered unsignaled, so both movements (e.g., moving up/down) were explicitly unpaired with the painful shock. Next, the extinction group continued training in the predictable context, but the painful movement was no longer followed by shock; the context exposure group continued training in the unpredictable context but unpredictable shocks were omitted. The control group continued (acquisition) training in both contexts. Results showed more fear reduction to the CS+ movement in the extinction group than in the control group. In the unpredictable pain context, exposure to threatening contexts/situations decreased generalized pain-related fear. Interestingly, fear ratings for both unpredictable movements also diminished after context exposure. This means that movements that were never genuine predictors of pain, but that were performed in threatening/unsafe, started to elicit more fear than similar movements in a safe context. This “irrational fear” of technically safe movements was extinguished following context exposure (i.e., reducing generalized pain-related fear). Conceptualizing unpredictable pain as a laboratory model for generalized pain disorders, a feasible treatment strategy might be to expose patients to increasing physical activity in their feared contexts or daily life environment. If you are interested, read the paper. Of course, other features that might influence extinction learning merit further scientific attention in order to optimize exposure treatments e.g., subtle safety behaviors (Volders et al., in press), mood and motivational factors (Karsdorp & Vlaeyen, 2011), and individual differences in inhibitory capacity.

About Ann Meulders

Ann Meulders 150x150 Extinction is the Path to the Light Side of the ForceAnn is currently working as a postdoctoral fellow in the Research Group on Health Psychology at University of Leuven. During her PhD research (at the Center of Learning and Experimental Psychopathology) she was already flirting with fundamental learning theory and had a particular crush on classical conditioning models to experimentally study fear and anxiety in the lab. As true love never fades, her current ambition is to apply her fear conditioning expertise in the domain of chronic pain. Ann is particularly interested in pain-related fear conditioning and pain unpredictability, and more specifically in how predictable vs. unpredictable pain affects the acquisition, generalization, and extinction of pain-related fear and avoidance as well as how it alters the perception of pain itself.

References

Karsdorp PA, & Vlaeyen JW (2011). Goals matter: Both achievement and pain-avoidance goals are associated with pain severity and disability in patients with low back and upper extremity pain. Pain, 152 (6), 1382-90 PMID: 21392886

Meulders A, & Vlaeyen JW (2012). Reduction of fear of movement-related pain and pain-related anxiety: An associative learning approach using a voluntary movement paradigm. Pain, 153 (7), 1504-13 PMID: 22617631

Volders, S., Meulders, A., De Peuter, S., Vervliet, B., & Vlaeyen, J.W.S. (in press). Does safety behaviour hamper the extinction of fear of movement-related pain? An experimental investigation in healthy participants. Behaviour Research and Therapy. 

Comments

  1. dear ann,
    are you able to tell me if the pain increases during the exercise with chronic pain sufferers? i’m curious because my experience (with an injured pelvic nerve) is that persisting eventually ends up in a flare up. i understand the fear and believe it does cause tension and stress but in times when i’m distracted and engaged in an activity that takes my awareness away from my pain, the pain only returns or interrupts and is stronger, like i’ve poked a wound. in fact most things i do put pressure on the nerve, its in such a core part of my body.
    thanks for sharing your knowledge.

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  2. Reducing pain-related fear once it has been acquired is quite difficult and often requires multiple therapy sessions. I agree that if you can overcome the patients initial mental fear, getting them to overcome the physical sensation is much easier.

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  3. stuart miller says:

    I really appreciated your comments Soula. Hopefully I can gain more insight from you, Ann and others. It didn’t seem like fear was a major factor in your return to activity but possibly the frustration/challenges with pacing and present limits to activity. I have had challenges in my choice of wording with some patients with complex and/or chronic pain who are wanting to return to meaningful activity (ex gardening or yoga that is more sedentary but may involve challenging positioning) and perceived needs to have to ‘complete’ a task or participate for a longer time than the body has adapted to. I love the ‘spring gardening analogy’ provided by the late Dr. Paul Brand and I do like the saying that ‘anything worth doing is worth doing poorly (initially)’ but it doesn’t necessarily translate well. Using a timer (if one is distracted) and graded positioning (chairs, blocks, aides) so that graded adaptation occurs is helpful (? I’m overstating the obvious) . Does anyone have suggestions ? To stay on topic re fear, I think, and the research shows, that voluntary graded aerobic activity is helpful for brain health and body adaptation but I really have challenges in wording and explanations with patients in which aerobic activity or ‘exercise’ has been tried before with significant flare-ups. It sometimes involves creativity to grade aerobic activity in different ways initially (especially when there is anticipatory fear). The book, Explain Pain, is brilliant for questions. (‘How many minutes would you be comfortable with to start ?’). It’s nice to have aerobic exercise machines with progressive loading (and different positions) and pools (with different temperatures) can be useful (? with anticipatory fear of water) – at some point it has to be meaningful or allow you to return to some form of meaningful activity to be used long-term. I think sometimes with neuropathic pain that the phrase ‘dress warmer than you think’ has helped. Any help ? Any comments ? Just looking for understanding and dialogue.

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    soula Reply:

    hi stuart,
    i have an incredible alexander technique physiotherapist. she knows words and how to incorporate them into any activity whether you want to call it exercise, daily movements, hobby etc etc. email me, i’m sure she won’t mind me giving you her contact details. i have many great experiences and teachings from her but one for example was repeating the word ‘hello’. this is how sensitive my issue was, before even attempting activity we practised uplifting words and observed how they felt and what happened to my body when i said ‘hello’ (as if to a friend). i believe she is truly brilliant with her work and if it’s communication you seek you should chat to her.
    on another note, ‘dress warmer than you think’… absolutely not. for the pudendal nerve it’s cold all the way. in fact sitting in cold water has proven a huge relief for me. no heat generating clothing, no doona on my lower back at night until i fall asleep. ice pack not as good but water cooled a larger area, what felt like the span of the nerve. bliss. when you think of what nerve blocks do then we must need cold. aren’t they a sort of cooling agent?
    email me if you wish. i have been monitoring the pudendal neuralgia for 5.5 years now!!! happy to help.

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  4. stuart miller says:

    Thanks Soula for the insight. I am always looking for help with language. I know that with more centralized inflammation that cooling can be helpful (the MS patients I work with know this extremely well – definitely not adviseable to do activity in a hot tub). It sometimes seems that central cooling is needed with peripheral warmth, warm during day, cold at night or warm compression (like paraffin wax baths with arthritic hands). I would appreciate a relevant article on the HPA axis and temperature. I still like contrast baths for helping with intense signalling from a peripheral source but as for the reasons it really works with some people, I’m not completely sure (maybe someone might have a more recent article). I’m glad that cooling helps you. I live in Canada so the extremes of temperature tend to dip into the minus but I don’t know if there is any relevance. I definitely notice that ‘the response to the Canadian cold’ can lead to restrictions in movement as well as irritation to the neck and shoulders and peripheral nerve irritation for some patients. Asking the question ‘is this dangerous? and how dangerous is it? is sometimes helpful even when it’s -40 degrees. I like the phrase ‘there is no bad weather, only bad clothing choices.’ In terms of the periphery, the role of the lymphatics in edema control is fascinating – arterial flow is helpful as is warmth and light compression but I haven’t read any recent articles on the lymphatic system. Dr. TJ Ryan’s work is great but I would appreciate if anyone has any recent articles. In terms of nerve blocks, I don’t think I know enough to refute that they are a cooling agent. To my understanding, they are dampening information (pardon the language). Any help from others ? Back to fear, I think that body language of the therapist as well as what they say can definitely be helpful or fear inducing. I really appreciated the role of practice of uplifting words prior to activity. Thanks !

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