Opinion – Suzana Herculano-Houzel: The brain economy, like the world’s, is limited by the supply of resources

The world infected by the current virus (because others will come, but that’s another story) has recently discovered the meaning and consequences of the expression “supply chains”: empty shelves and higher prices, when transport routes and distribution of products do not account for the demand for products. For now, the consequences are still mostly limited to luxury or superfluous goods; time, then, to learn from experience, before it is too late.

The lesson here is that scarce goods need to be recognized as such—and the source of scarcity may lie not in the good itself, but in the transport and distribution network that makes the good reach consumer units. It’s the difference between finding yourself living in a house with solar panels and batteries in hot, sunny weather in a city with a large, redundant power grid, or in a remote village whose electricity depends on a single cable from a single source — and your neighbors. they still insist on turning on electric shower and air conditioning every day. Residents of both locations may have the same abilities, desires and plans, but their ability to achieve is limited by the energy they receive.

This also seems to be the case with the brain, as I have just discovered.

My new scientific passion is the economics of the brain: not how the brain deals with the Economy it creates in the world — the traffic and trafficking of scarce resources — but what the economics of brain tissue itself is like. How much energy does the brain use, and how does that compare to how much energy it has available? I have been working in collaboration with Douglas Rothman, an expert in brain metabolism at Yale University, and together we have just published, in a special issue of the journal Frontiers in Integrative Neuroscience, our discovery that even the brain’s economy, like that of the world, is limited. by offering resources.

Perhaps the idea seems obvious to the reader accustomed to scarcity of resources, but most neuroscientists operate on a very different premise: the idea that the energy brought to the brain by the blood is always abundant and in excess, compared to what is necessary for the activity of the brain. neurons. On the contrary, Doug and I have shown, using mathematical models of the distribution of oxygen to brain tissue, limited by the density of capillaries in the tissue, that the brain, even idly, is already working close to the limit.

The problem is that the brain doesn’t function like a muscle, which, at rest, has closed capillaries, like collapsed hoses, that automatically open when arteries respond to muscle activity by pumping more blood. In the case of the brain, all the capillaries are always open, and the main hose, which is the internal carotid artery, always pumps what it can. Result: the brain does what it can with the constant amount of blood it receives.

What does that mean? I leave you thinking about it, dear reader whose brain is already running at full throttle all the time. Come back here in two weeks and I’ll explain…