“The common conception that the brain is primarily for thinking, or other cognitive processes, is potentially misleading... neuroscience may benefit from a theoretical structure that centers on basic questions of how the brain coordinates and efficiently regulates the body.”
What if our entire understanding of the purpose of the brain is wrong?
By default, we have come to believe the main task of a brain is to think, to wield intelligence, to learn and remember and feel. Is this not what our own brains do the most?
It turns out it’s not nearly so simple, and by focussing on just our own perceptions - our conscious mind - we have completely ignored perhaps its most fundamental role: regulation of bodily systems to keep us alive.
I’m talking about the system of allostasis, or predictive regulation.
Unlike homoeostasis, where the body reacts to problems when they arise, allostasis is all about predicting the bodies needs ahead of time and adequately preparing for them, regulating internal systems to manage energy and resource-use. It’s tasked with efficient logistics planning, ensuring the supply is available at times when demand is predicted to rise.
This makes for a very obvious evolutionary purpose to the brain: it likely evolved as a means of managing the complex biochemistry of large multi-cellular organisms, and consciousness arose from the eventual complexity of its allostatic functions.
Although not a new idea, allostasis seems to be going through a bit of a revival.
According to an article recently published in Neuron Volume 113 (Issue 24), Jordan Theriault et al. argue that thought and consciousness might be a case of exaptation, a kind of happy accident of evolution which turned out to be useful in its own right.
If we adopt this "allostasis-first" lens, the very things we traditionally call "the mind" - our emotions, awareness, even sensations - appear to be low-resolution readouts of our metabolic state. Your mood, for instance, may function as a low-dimensional "allostatic barometer," a summary of how efficiently your brain is managing your body’s internal energy budget.
Even "stress" loses its purely psychological weight. In this biological framework, stress is simply the brain predictively issuing commands to deliver glucose and oxygen to your tissues in anticipation of a metabolic outlay. It is a value-neutral preparation for action should action be necessary.
This is not to suggest that these barometers and predictions are always correct. Like any sensor, they can be fed faulty data or be improperly calibrated. Like some safety systems installed on aircraft, a bad sensor can kick off a distinctly inappropriate response (see: Boeing 737 Max)
Still, this regulatory priority is etched into the very architecture of the human cortex. The brain is organised along a structural gradient that stretches from a "limbic core" to our primary senses. At this limbic core, signals are abstract and low-dimensional compressed summaries of the body’s collective needs. As these signals flow outward toward the motor and sensory systems, they "decompress" into the specific particulars required to move a muscle or adjust a heart rate.
Simultaneously, the firehose of raw sensory data coming from the world is compressed as it travels inward. It is stripped of its noise and categorised into meanings, with the most salience being placed on its allostatic value, i.e “what does this sight or sound mean for my survival?”
Ultimately, this shift in perspective dissolves the artificial wall we have built between the mental and the physical: we are not merely a mind inhabiting a body. The mind and body are a unified system.
What happens if we look at cognitive decline using this allostatic lens? Take Alzheimer’s, one of the main examples cited in the paper: the perspective shifts from a system breaking down, to a series of desperate, yet calculated, sacrifices.
Higher-order cognition uses up a fair bit of energy, but is non-essential for staying alive. It also produces a lot of waste products, due to the rather-inefficient method of anaerobic metabolism of glucose products into ATP (up to 15 times more inefficient than the aerobic alternative.). These waste products need to be removed regularly, mostly via the bloodstream, otherwise they can build up and cause havoc.
However, as we age, our vascular health naturally declines and becomes less efficient at this waste-removal task.
So when a system is faced with a situation where the waste produced by this high-energy, higher-order cognition begins to out-pace the brains ability to remove that waste, the authors suggest we might be forced into an “allostatic trade-off”, with the allostasis mechanism automatically rationing the amount of glucose supplied to the brain to reduce the overall demand on the vascular system.
If brain waste clearance is compromised, then it may be allostatically beneficial for the brain to downregulate glucose metabolism by restricting the transport of glucose into neurons and across the blood-brain barrier. Consistent with this, in older adults, glucose uptake and glucose transporter density (GLUT1 and GLUT3) decline following amyloid accumulation but before the appearance of cognitive decline.
That trade-off might allow the body to physically live longer than it otherwise would, but at what cost?
Put your email in this box. Just trust me.
Alzheimer’s results in the gradual destruction of the inner self; cognitive ability, memories, beliefs, even volition, eventually slip away.
However, the allostasis model does suggest that approaching Alzheimer’s as an energy-management syndrome centred around glucose and the function of the vascular system in general might lead to better treatments. Perhaps, if we work on improving vascular system health, as well as finding ways to clear up debris as we presently do, this combined, systems-driven approach might give us a fighting chance.
Everything psychological that a brain accomplishes—sensing, perceiving, thinking, feeling, deciding, acting—can be considered a means to the end of its core ongoing task: coordinating and regulating internal bodily systems, as an organism navigates a constantly changing but only partly predictable world.
The mind is a prediction machine. That’s its purpose: to predict what happens next, what’s coming down the pipeline, where and when we need energy levels to be at their highest readiness and when we will need to rest. The mind is all about forward-projection, and from birth it is continuously training against the incoming data to identify sequences and patterns in time.
As a fellow Substacker mentioned recently, it’s possible that consciousness arises only when the subconscious mind is inadequate to the task of managing one particular system in a particular context.
Take breathing.
You breathe autonomically, and are entirely unconscious of it most of the time. However, now that I’ve mentioned it and brought it to your attention, it will have entered your conscious awareness. You’re now aware of the action of your diaphragm, as it works to expand and contract the lungs. You can now choose to alter its action, slow it down, speed it up, or hold your breath for a period of time.
This also happens at times of physical exertion, or when your head is underwater, or your conscious mind perceives the air around you to be unsafe to breathe: your conscious mind takes over to analyse the situation and decide when and how to take your next breath.
Soon, likely in the next few minutes, it will return to subconscious autonomic action, and your conscious mind will focus on other things.
If allostasis is the brain’s primary job, then it must prioritise the body’s internal state over external data. This leads to a phenomenon called sensory gating.
Emerging evidence suggests that our distance senses - vision, hearing, and touch - are synchronised to our internal rhythms.
We’re not perceiving the world at a constant, steady rate; the brain “samples” the environment in time with the cardiac cycle. In fact, so much about our perception is aligned with such cycles.
For instance, during systole (when the heart contracts and pumps blood), we are statistically slower and less accurate at detecting visual or auditory stimuli. The brain actually suppresses external input during these moments of high internal pressure, effectively “blinking” our sensory awareness. We saccade - rapidly move our eyes - more frequently during systole, but we fixate and actually process the world during diastole, when the heart is at rest.
Breathing acts in a similar way, functioning as a global “oscillatory pacemaker”. It synchronises neural signalling across the brain, impacting everything from memory consolidation in the hippocampus to how we process emotion and make decisions.
Self-regulation isn’t a silo, either. Humans are social animals, we have evolved to “outsource“ some of our allostatic regulation to others.
This is known as Social Allostasis, and resembles the concept of co-regulation.
When we are in close, trusting relationships, our companions help regulate our heart rates, breathing, and even our core temperature, effectively reducing the metabolic “tax” on our own systems. The sense of safety these relationships provide allows us to operate at a reduced level of vigilance.
This explains why loneliness is so physically toxic; without a social network to help distribute the load, our brains can remain stuck in a highly costly state of vigilance, which eventually wears down the system. In the context of Alzheimer’s, it’s one way to explain why strong social support shows a slower rate of cognitive decline; the social environment can help regulate a struggling internal energy budget.
In short: we see and hear with our hearts, think with our lungs, and heal with our friends.
Thank you for joining me on today’s short dive into some new research that I’ve been looking into. What do you think about the Allostasis model? I’d love to get your insights, let me know in the comments!
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