The Energing Rennaissance In Neuromancy

nature |  A human brain slice is placed in a microscope to visualize nerve fibres. Credit: Mareen Fischinger

Imagine looking at Earth from space and being able to listen in on what individuals are saying to each other. That’s about how challenging it is to understand how the brain works.

From the organ’s wrinkled surface, zoom in a million-fold and you’ll see a kaleidoscope of cells of different shapes and sizes, which branch off and reach out to each other. Zoom in a further 100,000 times and you’ll see the cells’ inner workings — the tiny structures in each one, the points of contact between them and the long-distance connections between brain areas.

Scientists have made maps such as these for the worm¹ and fly² brains, and for tiny parts of the mouse³ and human⁴ brains. But those charts are just the start. To truly understand how the brain works, neuroscientists also need to know how each of the roughly 1,000 types of cell thought to exist in the brain speak to each other in their different electrical dialects. With that kind of complete, finely contoured map, they could really begin to explain the networks that drive how we think and behave.

Such maps are emerging, including in a series of papers published this week that catalogue the cell types in the brain. Results are streaming in from government efforts to understand and stem the increasing burden of brain disorders in their ageing populations. These projects, launched over the past decade, aim to systematically chart the brain’s connections and catalogue its cell types and their physiological properties.

It’s an onerous undertaking. “But knowing all the brain cell types, how they connect with each other and how they interact, will open up an entirely new set of therapies that we can’t even imagine today,” says Josh Gordon, director of the US National Institute of Mental Health (NIMH) in Bethesda, Maryland.

The largest projects started in 2013, when the US government and the European Commission launched ‘moonshot’ efforts to provide services to researchers that will help to crack the mammalian brain’s code. They each poured vast resources into large-scale systematic programmes with different goals. The US effort — which is estimated to cost US$6.6 billion up until 2027 — has focused on developing and applying new mapping technologies in its BRAIN (Brain Research through Advancing Innovative Neurotechnologies) Initiative (see ‘Big brain budgets’). The European Commission and its partner organizations have spent €607 million ($703 million) on the Human Brain Project (HBP), which is aimed mainly at creating simulations of the brain’s circuitry and using those models as a platform for experiments.