Stargazing in the brain: 'Star-like' cells display unique activity
patterns

Date:
February 9, 2022
Source:
Okinawa Institute of Science and Technology (OIST) Graduate
University
Summary:
The way we experience the world occurs due to complex and intricate
interactions between neurons in the brain. Now, a study suggests
that astrocytes -- star-shaped, non-neuronal cells in the brain
-- might also play an important role in processing information,
and perhaps even memory.



FULL STORY ==========================================================================
The way we experience the world occurs due to complex and intricate interactions between neurons in the brain. Now, a study, published
9th February 2022 in Science Advances, suggests that astrocytes --
star-shaped, non-neuronal cells in the brain -- might also play an
important role in processing information, and perhaps even memory.


========================================================================== Using advanced imaging and analysis techniques, researchers from the
Okinawa Institute of Science and Technology Graduate University (OIST)
recorded signaling within single astrocytes at a previously unseen level
of detail and speed in the brains of awake mice.

Their findings, including ultra-fast signals on par with those seen in
neurons and patterns of signaling activity that correspond to different behaviors, suggest that astrocytes may play a crucial role in many
functions of our brain, including how we think, move, and learn.

"If these implications are true, it will fundamentally transform how
we think about neuroscience, and the way the brain works," said first
author Dr.

Leonidas Georgiou, a former PhD student in the Optical Neuroimaging Unit
at OIST.

When we picture our brain, we typically imagine a messy tangle of long,
wire- like neurons that send electrical signals to each other across
different regions of the brain. But neurons only make up half the cells
in our brain.

Crammed into all the remaining space between the jumble of neurons are
many other types of brain cells, including astrocytes.

"Compared to neurons, astrocytes have received very little attention. It
was thought that astrocytes are just helper cells, supplying the neurons
with nutrients and removing their waste," said Professor Bernd Kuhn,
senior author and head of the Optical Neuroimaging Unit.



==========================================================================
But in recent years, there's been increasing amounts of evidence that astrocytes can listen to chemical messages sent between neurons at
synapses, and can respond with their own signals, providing an extra
layer of complexity to how our brain receives and responds to information.

Still, the previously detected signals in astrocytes were about ten
times slower than signals seen in neurons, with scientists therefore
believing the cells were too slow for information processing.

However, by developing a new toolkit that allows the study of astrocyte activity in awake mice with unprecedented detail, the researchers at
OIST showed for the first time that astrocytes generate signals in vivo
which are as fast as that of neurons, lasting fewer than 300 milliseconds.

Their toolkit relied on a new discovery: that a virus regularly used
for gene therapy could "jump" from neurons to connected astrocytes. The scientists used an adeno-associated virus that contained a gene that
makes infected cells fluoresce. The fluorescence increases in intensity
in the presence of calcium - - an important indicator of signal activity
within living cells.

Once labelled, the research team were able to use a powerful, homebuilt microscope to pinpoint and image a single astrocyte, over multiple days
for up to an hour at a time, while the mouse was awake and moving.



==========================================================================
The scientists then used an advanced computer program to analyze
the recorded images, allowing them to detect the never-before-seen
ultra-fast flashes of calcium signals, and evaluate signal patterns in
an unbiased way.

They found that sensory stimulation, by tickling the whiskers, resulted
in very little calcium signaling, while certain behaviors, like running
or walking, resulted in high levels of activity.

The scientists also realized that there were certain areas in the
astrocyte, or hotspots, where levels of activity were higher.

"These hotspot maps are like fingerprints -- for a specific behavior,
they are stable over time, remaining the same over a period of days,
and unique to each astrocyte," said Dr. Georgiou.

Even more surprisingly, the team noticed that different behaviors
corresponded to unique hotspot patterns.

"So, when the mouse is resting, you see one pattern. And then when the
mouse is running, you see a different pattern," said Prof. Kuhn.

One hypothesis suggested by Prof. Kuhn is that these hotspot maps
could represent memory engrams -- a pattern that represents a specific
behavior or a memory. Different neuron networks are active during
specific behaviors or when learning and recalling information, which
could also change the activity of nearby astrocytes. Memory engrams are
still theoretical, and highly controversial, he acknowledged.

"We still don't know how memories are stored in a brain, but
it's incredible to think that it could involve astrocytes,"
he said. "It's likely too good to be true, but it's an
exciting hypothesis to follow up on." special promotion
Explore the latest scientific research on sleep and dreams
in this free online course from New Scientist -- Sign_up_now_>>> ========================================================================== Story Source: Materials provided by Okinawa_Institute_of_Science_and_Technology_(OIST)
Graduate_University. Original written by Dani Ellenby. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Leonidas Georgiou, Anai' Echeverri'a, Achilleas Georgiou and
Bernd Kuhn.

Ca activity maps of astrocytes tagged by axoastrocytic AAV transfer.

Science Advances, 2022 DOI: 10.1126/sciadv.abe5371 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220209154813.htm

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