Seeing the 'starry sky' in the brain: Astrocytes show unique activity patterns

• Researchers have developed a new toolbox that allows them to image individual astrocytes in the brains of awake mice at an unprecedented level of detail

• This study shows for the first time that in vivo, astrocytes produce calcium signals as fast as neurons, lasting less than 300 milliseconds

• The scientists also found that astrocytes have hot spots, where activity is more frequent

• Heatmaps are stable over time, with unique patterns for specific behaviors

• These findings are potential evidence that astrocytes play a role in information processing and memory storage

The way we experience the world is due to the complex and complex interactions between neurons in the brain
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Using advanced imaging and analysis techniques, researchers at the Okinawa Institute of Science and Technology (OIST) have recorded signals within individual astrocytes in the brains of awake mice with unprecedented detail and speed
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Their findings, including patterns of signaling activity that correspond to the ultrafast signals seen in neurons and different behaviors, suggest that astrocytes may play a key role in many functions of our brain, including how we think, move and learn
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"If these implications are correct, it will fundamentally change the way we think about neuroscience and the way the brain works," said first author Leonidas Georgiou, PhD, a former doctoral student in OIST's Optical Neuroimaging Unit
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When we picture our brains, we usually picture a jumble of long, thread-like neurons that send electrical signals to each other in different areas of the brain
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"Compared to neurons, astrocytes have received little attention
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But in recent years, there has been growing evidence that astrocytes can listen at synapses for chemical messages passed between neurons and can respond with their own signals, which are used by our brains to receive and The way you respond to messages adds an extra layer of complexity
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Still, the signals previously detected in astrocytes were 10 times slower than those detected in neurons, so the scientists thought these cells were too slow for information processing
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However, by developing a new toolkit to study astrocyte activity in awake mice in unprecedented detail, OIST researchers have shown for the first time that the speed at which astrocytes generate signals in vivo is comparable to that of neurons.
Just as fast, lasting less than 300ms
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Their toolkit relies on a new discovery: A virus often used in gene therapy can "jump" from neurons to connected astrocytes
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Once labeled, the research team was able to use a powerful home-made microscope to precisely locate and image individual astrocytes for hours at a time over several days while the mice were awake and moving
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The scientists then used an advanced computer program to analyze the recorded images, allowing them to detect never-before-seen ultrafast flashes of calcium signals and assess signal patterns in an unbiased way
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They found that the sensory stimulation produced by tickling the whiskers produced only a small calcium signal, while certain behaviors, such as running or walking, produced high levels of activity
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The scientists also realized that there were higher levels of activity in certain specific areas, or hot spots, of astrocytes
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"These heatmaps are like fingerprints - for a particular behavior, they are stable over time, remain constant over time, and are unique to each astrocyte," Dr Georgiou said.

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Even more surprising, the team noticed distinct patterns of hotspots corresponding to different behaviors
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"So, when the mouse is resting, you see one pattern
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One hypothesis proposed by Professor Kuhn is that these heatmaps could represent memory imprints—patterns that represent specific behaviors or memories
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"We still don't know how memories are stored in the brain, but incredibly, it may be related to astrocytes," he said
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article title

Ca+ activity maps of astrocytes tagged by axoastrocytic AAV transfer