Thursday, 29 January 2015

Ways in which our brain influences our awareness

"Ouch, that hurt!"

Let's take a moment to look at this simple expression.

As journalist Oliver Burkeman said in this lovely article in the Guardian recently, (slightly paraphrased) "when you stub your toe on the dining table, your nerve fibres shoot a message to your spinal cord, in turn sending neurotransmitters to the thalamus, which activates (among other things) your stress response. Ok, but what about the agonising flash of pain? And what is pain, anyway?" To that I would add the question "what about the times we stub our toe and don't even realise...?" What's happening?

Let's first look at the neuroscience. 

As Burkeman says, when we stub our toe these pain signals (like any other sensation like heat or pressure) travel from the peripheral nerves to the spinal cord and up into the brain. Modern neuroscience tells us the spinal cord contains special nerve fibre bundles that serve as "gateways" to the brain, controlling whether or not a signal gets passed on or not. These gateways have the ability to mute or amplify sensations depending on the relative mix of physiological and, importantly, psychological stimulus input. So what does this mean?

Opening and closing the gates

There's a nice example given here in the book "Relaxation, Meditation, & Mindfulness: A Mental Health Practitioner's Guide" by Jonathan Smith. Let's first imagine you're at home playing with your young niece and she suddenly grabs your hand tightly, squeezing your fingers and your knuckles together. Ouch! You feel a sharp sensation of pain. These are your peripheral nerves sending the signals to your brain.

Now imagine as she grabs your fingers and squeezes, she giggles and plants a wonderful smiling kiss on your cheek! This time you barely notice her squeezing your fingers – this is because the pleasant distraction (initially) closes the nerve gateways as you attention is redirected. The feedback from subsequent thoughts and feelings, such as "she's such a wonderful kid!”, continue to hold the gates closed.

Then she lets go of your hand and you see that your fingers have gone white! But by now your brain has realised that the squeeze was completely innocent and you're not injured. What might otherwise be experienced as pain may instead be experienced as a strong tingling sensation.

Now imagine you're sitting on your sofa with your arm are dangling over the side out of sight. Suddenly you feel something tighten around your fingers and knuckles. Not knowing what it is you feel a stab of pain. Then come the associated thoughts: "it's the dog!", and the pain grows stronger. You feel a shot of fear over possible damage to the skin or infection, and it gets even stronger. This time the pain sensations, and the feedback from subsequent thoughts and feelings, blow open the pain gates and you're all too consciously aware of it all. Perceived threats are very powerful activators of the brain's systems.

Thankfully the example given in the book gives a positive ending to this scenario: you turn to look for the offending dog and discover it is just your niece again. The gates start to close, the pain goes away, hastened by a burst of laughter triggering a release of endorphins and a further closure of the gates!

So there's an interplay between the different types and levels of stimulus inputs, including from our nerves and sense organs, emotions, endorphins, and thoughts, and it's all affected by how our attention is directed. This interplay controls the state of the gateways, and therefore our experience of pain. This is known as "gate-control theory" after Ronald Melzack and Patrick Wall who came up with it in the 1960s (Melzack & Wall, 1965, 1982).

The reticular activating system

In the journey up to the brain, the next area the our sensations have to pass through is the brain stem. This area is responsible for (1) regulating most of the body's automatic functions (breathing, heartbeat, blood pressure, etc), and (2) relaying information to and from the brain to the rest of the body. It plays an important role in consciousness, awareness and movement (and it is only when brain stem function is permanently lost that a person is confirmed as dead.)
An important area in the brain stem for us in the mindfulness business is the reticular activating system (RAS) since it can have a strong influence on what we actually become aware of. 
Sorry, the reticular what...?!

The reticular activating system, or RAS (but not RAS) is also thought to play a role in many important autonomic functions, including regulating sleep and wake, arousal and breathing. However, perhaps its most important function is its ability to focus our attention on something. It is the portal through which nearly all sensory information enters the brain, and it acts as an initial filter to all this incoming information to stop us getting overloaded. It dampens down repeated or excessive stimuli, and flags up any crucial information that threatens survival or is just new and different. It's part of our internal editor.

Imagine walking down a busy shopping street with a blister on your foot. You've been walking all day, and with your attention on navigating the crowds and getting to the next shop you filter out the soreness on your foot – thanks to your RAS. Then someone in the crowd treads on your foot and boom, suddenly you notice! That again is your RAS working for you.

The sense gates in the spinal cord and the RAS in the brain stem are therefore similar in function. The RAS operates at a slightly higher level though, filtering and editing higher level sensations and thoughts.

So what is pain?

I think the above examples illustrate a few different aspects of pain. There are the nerve impulses that are relayed up the spinal cord to the pain gateways. Depending on our physical and emotional state, these gates open letting the pain sensation through, or don't, blocking or modifying the signal. Then there's our reticular activating system which acts at a higher level to dampen down repeated or excessive stimuli, or flag up any life-threatening (or just new and exciting) information.

Assuming that the pain signals pass through all the way to our awareness, then we perceive pain. Then come all the layers of associated thoughts and emotions: "I'm so stupid, why did I burn myself again?", "Why won't this pain go away?", "I hate this pain!", "I must have done something bad to deserve this", etc.

Someone wise once said "pain is inevitable, suffering is optional". A considerable proportion of what we perceive as pain arises through our anxious desire to suppress it, and that's where our mindfulness practice can really work in our favour. The Buddha said, “When we’re touched with a feeling of pain, we feel sorrow, grief, and, beating our breast, become distraught. We feel two pains, physical & mental. Just as if we were to shoot a man with an arrow and, right afterward, were to shoot him with another one”. The physical pain may be unavoidable, adding the mental pain is our choice.

Influenced awareness

So our unconscious systems can modify our sensory inputs before we're even conscious of them. A recent article I read (p26) paraphrased this as "the eyes only see and the ears only hear what the brain tells them" – in short we all pick opinions then find data to support these beliefs and this becomes our reality. Since our mindfulness practice is all about increasing awareness and knowledge of ourselves and how we interpret reality, it's important to know about all these unconscious influences so we can recognise them when we feel their effects.

I am a member of the Zenways sangha led by Zen master Daizan Roshi, and I teach meditation, mindfulness and yoga at the ZenYoga studio in Camberwell, London. See my website for further details.

I'd love to hear from you

Perceptions on your pain gateways? Reflections on the reticular activation system? Leave a comment below, join the discussion.

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