Using Heart rate monitoring to help with pacing.

[Utsikt]

The brain is of course involved in received and integrating those signals, but the point @Snow Leopard is making is that any "accounting" the brain does is primarily a matter of sorting out sensory input. If it was solely a predictive model in the brain, you should be able to get accurate results regardless of whether or not the brain has access to that sensory input from metabolic-sensing afferents. Which is not what we see.

But accounting isn’t prediction. JE (to my understanding) is talking about keeping track of how much activity you’ve done. Where does the prediction come into play?

 

[Jonathan Edwards]

Or, the more parsimonious explanation would be that this activity has a pretty consistent impact on metabolic state, which is what the brain is actually sensing.

But the brain still has to integrate over time in order for prolonged activity to be more of a problem than a brief burst. Just as it has to integrate over time to control weight. Which is presumably why we have leptin interacting with much the same place as T cells hang out in the subfornical organ!

And I personally doubt that my metabolic state is much different after walking 12,000 steps than after 3,000, but the way I feel is quite different.

 

[jnmaciuch]

But accounting isn’t prediction. JE (to my understanding) is talking about keeping track of how much activity you’ve done. Where does the prediction come into play?

I think the idea is whether the brain is keeping track of how much activity you've done without any metabolic sensory input, which is what is meant by "predictive modeling" and "accounting." I.e. the idea that the brain accountant creates a "predictive model" of how tired you should feel based on how many steps it knows you walked (from the visual or proprioceptive systems, I suppose?)

 

[Jonathan Edwards]

Quite apart from anything else there is circadian rhythm - which we all know about because after a certain number of hours our brains feel sleepy. The evidence for brains keeping track in terms of integrating over time seems to me to be pretty much first year biology stuff.

 

[Jonathan Edwards]

I think the idea is whether the brain is keeping track of how much activity you've done without any metabolic sensory input, which is what is meant by "predictive modeling" and "accounting."

I never said anything about predictive models and in fact it is one my biggest BÊTES NOIRS.

 

[jnmaciuch]

But the brain still has to integrate over time in order for prolonged activity to be more of a problem than a brief burst. Just as it has to integrate over time to control weight. Which is presumably why we have leptin interacting with much the same place as T cells hang out in the subfornical organ!

I don't understand this. All of that information is already integrated at the metabolic level. If you've had prior activity and not enough recovery time for e.g. redox balance to be adequately restored, then your metabolic state will actually be quite different. Leptin also acts at that metabolic level directly. Again, it's positing an additional unnecessary accounting mechanism

And I personally doubt that my metabolic state is much different after walking 12,000 steps than after 3,000, but the way I feel is quite different.

I can only say that's a false assumption. And what matters is not just the metabolic state of specific muscle cells, but also extracellular concentrations of metabolites reaching sensory neurons

 

[jnmaciuch]

I never said anything about predictive models and in fact it is one my biggest BÊTES NOIRS.

I was referring to predictive how Snow Leopard used it to describe your proposition

 

[Utsikt]

I think the idea is whether the brain is keeping track of how much activity you've done without any metabolic sensory input, which is what is meant by "predictive modeling" and "accounting." I.e. the idea that the brain accountant creates a "predictive model" of how tired you should feel based on how many steps it knows you walked (from the visual or proprioceptive systems, I suppose?)

That isn’t the only way to keep track of things, or the only way to utilise accounting, though. I understand that «accounting» is also a part of predictive models, but that doesn’t mean that any accounting = predictive model exists.

 

[jnmaciuch]

Quite apart from anything else there is circadian rhythm - which we all know about because after a certain number of hours our brains feel sleepy.

Actually it's tracked by the bidirectional relationship between SIRTs/clock genes and NAD/NADH ratios [edit: i.e. redox balance] This is the expertise of my former professor

 

[jnmaciuch]

That isn’t the only way to keep track of things, or the only way to utilise accounting, though. I understand that «accounting» is also a part of predictive models, but that doesn’t mean that any accounting = predictive model exists.

I think I inserted the word model where it wasn't actually necessary to get my point across. What JE is positing is that the brain keeps track of activity independently from sensing metabolic state--that's what I'm arguing against and that's what the previous use of the word predictive referred to

 

[Jonathan Edwards]

and not enough recovery time for e.g. redox balance to be adequately restored,

Is there a scrap of evidence for that in the relevant context?
We are talking about the context of normal daily activities where redox shifts seem pretty unlikely to be relevant. Can you quote evidence that they are?

 

[Jonathan Edwards]

Actually it's tracked by the bidirectional relationship between SIRTs/clock genes and NAD/NADH ratios

Yeah, integrated over time!

 

[Jonathan Edwards]

I was referring to predictive how Snow Leopard used it to describe your proposition

What was that? You started talking about predictive coding and stuff, which seems to me irrelevant to what I was talking about - keeping track over time.

 

[jnmaciuch]

Is there a scrap of evidence for that in the relevant context?
We are talking about the context of normal daily activities where redox shifts seem pretty unlikely to be relevant. Can you quote evidence that they are?

I'm sorry Jonathan, I don't know how else to explain that redox shifts occur every single time cells produce ATP. Which has been known since the 60s, and the [edit: evidence is expansive and] readily available. I apologize if I am using terminology which you are familiar with in different contexts--perhaps you are thinking of it more in terms of "crises" of redox balance occurring in certain diseases

Yeah, integrated over time!

Yes, though I apologize, I don't see what your point is. All metabolic information is inherently "integrated "over time at the metabolic level, no need for neural “timekeeping”

 

[jnmaciuch]

There is zero evidence, or even theoretical basis for the brain "keeping score" of exertion in a predictive way. It is just responding to the signals it is given (which help modulate activity, appropriate cardiovascular responses to further exertion etc). Those signals can be blocked in humans so we know it is not a memory/predictive based system.

There is no evidence that the hypothalamus does any sort of predictive energy accounting as JE suggests.

@Jonathan Edwards
emphasis my own. I don't think Snow Leopard is using it incorrectly here, just perhaps in a way different from what you intended

 

[Utsikt]

Again, it's positing an additional unnecessary accounting mechanism

Why is a brain accountant for physical activity «unnecessary»? A system for keeping track of the inventory in a warehouse isn’t unnecessary because it’s possible to just go and count the boxes, or because some at one isle will be able to keep perfect track of what’s happening in their proximity.

I think it would be quite beneficial for the organ that makes the body find food to be able to keep a rough tally of how much food it has «used» through activity so that the organism doesn’t starve to death, especially if food is hard to come by.

The alternative would be that every «signal» to eat are just (edit: immediate) responses to signals for things that are external to the brain. Is that really the case?

 

[jnmaciuch]

Why is a brain accountant for physical activity «unnecessary»? A system for keeping track of the inventory in a warehouse isn’t unnecessary because it’s possible to just go and count the boxes, or because some at one isle will be able to keep perfect track of what’s happening in their proximity.

I think it would be quite beneficial for the organ that makes the body find food to be able to keep a rough tally of how much food it has «used» through activity so that the organism doesn’t starve to death, especially if food is hard to come by.

The alternative would be that every «signal» to eat are just responses to signals for things that are external to the brain. Is that really the case?

I think there might be a misunderstanding--I'm not arguing against the capacity of the brain to receive or integrate that sensory input from other parts of the body. I'm arguing against the idea that the brain doesn't use [edit: any of] that input from metabolic state of other parts of the body in order to do this "accounting"

 

[Utsikt]

I think there might be a misunderstanding--I'm not arguing against the capacity of the brain to receive or integrate that sensory input from other parts of the body. I'm arguing against the idea that the brain doesn't use [edit: any of] that input from metabolic state of other parts of the body in order to do this "accounting"

I don’t think it has been argued that the brain doesn’t use signals from metabolic states. It would be brainless (excuse the terrible pun) to not utilise the available info.

What has been argued, if I understand JE correctly, is that some of the «experiences» or «outputs» from the brain are caused or modulated by the accounting, and not just as immediate 1:1 responses from input from the rest of the body.

 

[jnmaciuch]

What has been argued, if I understand JE correctly, is that some of the «experiences» or «outputs» from the brain are caused or modulated by the accounting, and not just as immediate 1:1 responses from input from the rest of the body.

There's certainly evidence that the thresholds of that "accounting" can be modulated by the brain. We know that hypothalmic hormone secretion changes in response to starvation, for example. But [edit: that modulation still acts on, and] still always requires, input from other parts of the body, particularly metabolic signals (though different signals than in e.g. muscle fatigue).

That's where I think we do have differing interpretations of JE's argument. Back to the walking example, we know that the brain can't accurately gauge physical exertion if you block input from metabo-sensing afferents. That is actually contradictory to what JE was arguing, which was that the "tallying" must happen from inputs that aren't metabolic in nature, based on the assumption (which I do not share, [edit: and I must admit, am still utterly baffled by]) that peripheral metabolic state isn't changing "all that much"--if I'm understanding correctly

 

[Utsikt]

There's certainly evidence that the thresholds of that "accounting" can be modulated by the brain. We know that hypothalmic hormone secretion changes in response to starvation, for example. But [edit: that modulation still acts on, and] still always requires, input from other parts of the body, particularly metabolic signals (though different signals than in e.g. muscle fatigue).

That's where I think we do have differing interpretations of JE's argument. Back to the walking example, we know that the brain can't accurately gauge physical exertion if you block input from metabo-sensing afferents. That is actually contradictory to what JE was arguing, which was that the "tallying" must happen from inputs that aren't metabolic in nature, based on the assumption (I do not share) that peripheral metabolic state isn't changing "all that much"--if I'm understanding correctly

Thank you for spelling that out for me - I needed it!