For decades, neuroscientists focused almost exclusively on only half of the cells in the brain. Neurons were the main players, they thought, and everything else was made up of uninteresting support systems.
By the 2010s, memory researcher Inbal Goshen was beginning to question that assumption. She was inspired by innovative molecular tools that would allow her to investigate the contributions of another, more mysterious group of cells called astrocytes. What she discovered about their role in learning and memory excited her even more.
The computers that run on human brain cells
At the beginning, she felt like an outsider, especially at conferences. She imagined colleagues thinking, “Oh, that’s the weird one who works on astrocytes,” says Goshen, whose laboratory is at the Hebrew University of Jerusalem. A lot of people were sceptical, she says.
But not any more. A rush of studies from labs in many subfields are revealing just how important these cells are in shaping our behaviour, mood and memory. Long thought of as support cells, astrocytes are emerging as key players in health and disease.
“Neurons and neural circuits are the main computing units of the brain, but it’s now clear just how much astrocytes shape that computation,” says neurobiologist Nicola Allen at the Salk Institute for Biological Studies in La Jolla, California, who has spent her career researching astrocytes and other non-neuronal cells, collectively called glial cells. “Glial meetings are now consistently oversubscribed.”
Out of the shadows
As far back as the nineteenth century, scientists could see with their simple microscopes that mammalian brains included two major types of cell — neurons and glia — in roughly equal numbers.
Twentieth-century technologies generated most of the excitement around neurons. Researchers studying the cells’ electrical activity showed how they create the complex networks that underlie all brain functions.
When neurons are activated, electrical signals zap down their length at lightning speed, causing their synapses to release chemical neurotransmitters. Some of these, such as glutamate, excite neighbouring neurons, whereas others, such as GABA (γ-aminobutyric acid), inhibit them. The development of a technique called patch clamping in the 1970s and 1980s, in which electrodes are inserted into individual cells to measure the flow of ions across membranes, let researchers probe this neurotransmission in unprecedented detail.
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