The brain's reward pathway is like a teeter-totter because…
Keith S. Taber
in your brain there is a teeter-totter like in a kids' playground…these neuroadaptation gremlins hopping on the pain side of the balance…the gremlins hop off …But if we …accumulate so many gremlins on the pain side of our balance …we've crossed over into the disease of addiction…we are craving because …it's the gremlins jumping up and down
Dr Anna Lembke talking on 'All in the mind'
(Original images by Image by mohamed Hassan and OpenClipart-Vectors from Pixabay)
Dr Anna Lembke, Professor of Psychiatry at Stanford University explained how addiction relates to dopmaine and the brain's reward pathway with an analogy of a see-saw. She was talking to Sana Qadar for an episode of the the ABC programme 'All in the Mind' called 'How dopamine drives our addictions'.
Analogies are used in teaching and in science communication to help 'make the unfamiliar familiar', to show someone that something they do not (yet) know about is actually, in some sense at least, a bit like something they are already familiar with. In an analogy, there is a mapping between some aspect(s) of the structure of the target ideas and the structure of the familiar phenomenon or idea being offered as an analogue. Such teaching analogies can be useful to the extent that someone is indeed highly familiar with the 'analogue' (and more so than with the target knowledge being communicated); that there is a helpful mapping across between the analogue and the target; and that comparison is clearly explained (making clear which features of the analogue are relevant, and how).
A fried brain
During the programme the interviewer (Qadar) uses a metaphor for how addiction influences brain chemistry:
Sana Qadar: "The problem is when we are becoming addicted to something, our brain's ability to naturally produce dopamine gets fried."
Anna Lembke: "So essentially what happens in the brain as we tip toward the compulsive cycle of overconsumption or addiction is that we start to down-regulate our own dopamine production and dopamine transmission in order to compensate for the ways that we are bombarding our brain's reward pathway with too much dopamine through ingestion of these incredibly potent and rewarding substances and behaviours."
What does Sana Qadar mean by 'fried'? Presumably not destroyed, as the subsequent interview suggests that recovery is possible (see below) – although the brain's ability to naturally produce dopamine would surely not recover from actual frying. So, perhaps, fried means disturbed, or damaged? Given the following dialogue it might mean thrown out of balance.
Perhaps Qadar was thinking of the brain as circuitry as the term is commonly applied to damaged circuits (I think the term derives from damage caused by overheating, as can happen when there is a 'short' for example, which does stop the 'fried' components functioning permanently). So, perhaps for Qadar this is a dead metaphor – a term which started as a metaphor but which, with habitual use, has come to be treated as having literal meaning – at least in relation to electrical circuits and, by analogy, brain circuitry?
(Images by OpenClipart-Vectors and y Roger YI from Pixabay)
Balancing those gremlins
What I found especially interesting is the way Dr Lembke made extensive use of an analogy in her explanation, much in the way teacher might keep referring back to the same metaphor or analogy or model when introducing an abstract topic.
Sana Qadar tells listeners that "to explain how this process unfolds in the brain's reward pathway, Dr Lembke uses the analogy of a teeter-totter or seesaw":
"Because pleasure and pain are processed in the same part of the brain and work like opposite sides of the balance, it means for every pleasure there is a cost and that cost is pain.
So, if you imagine that in your brain there is a teeter-totter like in a kids' playground, that teeter-totter will tip to one side when we experience pleasure, and the opposite side when we experience pain.
But no sooner has that balance tipped to the side of pleasure, for example when I eat a piece of chocolate, then my brain will work very hard to restore a level balance or what neuroscientists call homeostasis. And it does that not just by bringing the balance level again but first by tipping it an equal and opposite amount to the to the side of pain, that is the after-effect, the come-down. I imagine that as these neuroadaptation gremlins hopping on the pain side of the balance to bring it level again.
Now, if we wait long enough, the gremlins hop off and homeostasis is restored as we go back to our baseline tonic level of dopamine firing. But if we continue to ingest addictive substances or behaviours over very long periods of time, we essentially accumulate so many gremlins on the pain side of our balance that we are in a chronic dopamine deficit state, and that is essentially where we get when we've crossed over into the disease of addiction.
Dr Anna Lembke talking on 'All in the mind'
As part of the programme of treatment Dr Lembke has developed for those suffering from additions she often recommends a period of complete abstinence – asking her clients to abstain for at least 30 days
Because 30 days is about the minimum amount of time it takes for the brain to restore baseline dopamine firing. Another way of saying this is 30 days is about the minimum amount of time it takes for the gremlins to hop off the pain side of the balance so that homeostasis or balance can be restored.
… I think in many people it is possible with abstinence to reset the reward pathway, the brain has an enormous amount of plasticity.
Dr Anna Lembke talking on 'All in the mind'
Abstinence is obviously not easy when the person is constantly faced with relevant triggers, as
"…what happens when we are triggered is that we release a little bit of dopamine in the reward pathway. … But if we wait long enough, those gremlins will hop off the pain side of the balance, and balance is restored….we are craving because we are in a dopamine deficit state, it's the gremlins jumping up and down on the pain side of the balance. But if we can just wait a few more moments, they will get off, homeostasis will be restored and that feeling will pass."
"…It's a fine line between pleasure and pain
From the lyrics of the song 'Pleasure and Pain' (covered by Manfred Mann's Earth Band), by Holly Knight & Michael Donald Chapman
You've done it once you can do it again
Whatever you've done don't try to explain
It's a fine, fine line between pleasure and pain.."
It's a fine line between pleasure and pain
Sana Qadar suggests that certain kinds of pain can actually be good for us. From a biological perspective this is clearly so, as pain provides signals to motivate us to change our behaviour (move away from the fire, put down the very heavy object), but that is not what she is referring to. Rather, that "Dr Lembke says it has to do with the fact that pleasure and pain are processed in the same part of the brain":
Well, just like when we press on the pleasure side of the balance the gremlins hop on the pain side and ultimately shift our hedonic setpoint or our joy setpoint to the side of pain, it's also true that when we press on the pain side of the balance, so we intentionally invite psychologically or physically painful experiences into our lives, that those neuroadaptation gremlins will then hop on the pleasure side of the balance and we will start to up-regulate our own endogenous dopamine, not as the primary response to the stimulus but as the after-response
…I'm absolutely not talking about extreme forms of pain like cutting [which is] not a healthy way to get dopamine
…[For example] Michael was somebody who was addicted to cocaine and alcohol, and got into recovery and immediately experienced the dopamine deficit state, those gremlins on the pain side of the balance, he was anxious, he was irritable, and he also felt very numb, kind of an absence of emotions, which was really scary for him.
And he serendipitously discovered in early recovery that if he took a very cold shower, that created for him the same kinds of feelings, in a muted way, that he used to get from drugs, so he got into this practice of every morning taking a cold shower, and it worked great for him."
Dr Anna Lembke talking on 'All in the mind'
Gremlins, indeed?
Of course there is no see-saw in the brain, but a see-saw is a familiar everyday object that people understand can be balanced – or not. And that if more children (of similar size) load up one side than the other it will be out of balance – and it will only level up once the loads are balanced.
Strictly, there are some complications here with the analogue. If the children are at different distances from the fulcrum that will change their turning effect (so two children could balance one of similar mass according to where they are positioned). Similarly, when the moments are balanced the see-saw will not necessarily be level: as 'balance' means no overall turning effect. So, if the see-saw was already at an angle to the horizontal, loading it up in a balanced way should not shift it back to being level.
Perhaps there is something comparable in the reward system to whereabouts children sit on the see-saw – (perhaps some synapses are more sensitive to the effects of dopamine than others?), but this would be over-complicating an analogy that is intended to offer a link to a simple everyday phenomenon.
Are gremlins like children – do they come in different sizes? Perhaps it seems a little childish even to talk of such things in the brain. But there was once a strong (if discouraged these days 1) tradition of considering a homunculus, a little observer, inside the brain as if in a control room. Moreover, if the lauded physicist James Clerk Maxwell could invoke his famous demon to explain aspects of thermodynamics, we should not censure Lembke's metaphorical gremlins.
If this comparison was being used as a teaching analogy in a formal course, then we might want a more careful setting out of the positive and negative aspects of the analogy (those things that do, and do not, map across from the see-saw to the reward system). But Dr Lembke is not trying to teach her clients to pass tests about brain science, but rather give them a way of thinking about their problems that can help them plan and change behaviour – that is, a useful and straightforward model they can apply in overcoming their addictions.
To find out more
Prof. Lembke was talking about a very important topic and here I have only abstracted particular comments to illustrate her use of the analogy. For a fuller account of the topic, and in particular Prof. Lembke's clinical work to help people struggling with addiction, please refer to the full interview.
Work cited:
- Nguyen JD, Duong H. Neurosurgery, Sensory Homunculus. [Updated 2021 Jul 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549841/
Note
1 The term is still use, but in a somewhat different sense:
"in neuroanatomy, the cortical homunculus represents either the motor or the sensory distribution along the cerebral cortex of the brain. The motor homunculus is a topographic representation of the body parts and its correspondents along the precentral gyrus of the frontal lobe. While the sensory homunculus is a topographic representation of the body parts along the postcentral gyrus of the parietal lobe."
Nguyen and Duong, 2021
So, nowadays we each have two 'little men' in our brains.
