This is Scientific Americans 60 Second Science.

I'm Steve Mursky.

Got a minute?

They're like the Pac-Man of our brain.

Harvard Neuroscientist Beth Stevens talking about Gleea cells which make up more than half

the human brain. This week Stevens got a MacArthur fellowship the so-called Genius Grant

for her studies of Glee. These cells are incredibly responsive to damage or injury.

They can protect our brain by, for example,

clearing bacteria or debris in the brain in the case of injury and disease.

Until about 10 years ago, almost all of the research devoted to these cells was in these contexts.

We discovered that there was another role for these cells in the normal healthy brain in particular during development.

So a synapse is a junction of communication between two neurons.

It's how neurons talk to each other.

We're actually born with an excess of synaptic connections and

through this normal developmental process called pruning a large number of these

extra synapses get permanently removed or eliminated while others get strengthened and maintained.

These microglial cells were in fact engulfing or eating these extra synapses.

So these cells are necessary to do this and now of course we're trying to better understand how it is

that they know which synapse to prune and which synapse to leave alone. A hallmark of

many neurodegener of diseases including Alzheimer's disease is the early loss of

synaptic connections or synapses.

And what's most striking about this is is thought

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