Scientists discover cells that filter and sharpen spatial signals

Date:
August 6, 2020
Source:
Institute of Science and Technology Austria
Summary:
How do you keep orientation in a complex environment, like the city
of Vienna? You can thank your brain's 'global positioning system'
(GPS), the hippocampus, for this sense of orientation. To further
understand its functions, scientists have analyzed single neurons
of this GPS in mice.

They discovered that so-called granule cells filter and sharpen
spatial information.



FULL STORY ==========================================================================
The hippocampus is a region within the brain that contains many
neurons that help us to navigate in space. This leads to the
nickname of this area: the GPS of the brain. The higher areas
of the cortex send information packages to the hippocampus to
generate location signals. However, not all packages contain relevant information. Therefore, the hippocampus needs to have a bouncer in place
to select incoming signals. Such a gatekeeper could be the granule cell,
a type of neuron situated at the entrance of the hippocampal circuit.


========================================================================== Identifying the correct cells IST Austria Professor Peter Jonas,
Xiaomin Zhang, and Alois Schlo"gl started to examine neuronal signals
in granule cells. However, the main problem was cell identification. In
the past, experts could not guarantee that they correctly identified
the cells. "Since this region is densely packed with various types
of neurons, it is technically challenging to identify granule cells,
the cells we were interested in," says Xiaomin Zhang, the first author
on the paper. This makes it very difficult to distinguish between the
activity of granule cells from that of other types of neurons located in
the same region. Furthermore, granule cells typically show very sparse
activity despite a vast amount of them. Thus, other cell types with
higher activity levels could dominate the picture.

Gatekeepers of the hippocampus To record the incoming and outgoing
signals of the granule cells, the scientists developed a novel recording technique and machine learning algorithm to decode these signals. To unequivocally identify the neurons, cells were filled with a tracer
during recording. In total, they recorded from almost a hundred granule
cells, generating a large data set that describes the activity of this important type of cell. They found that a majority of neurons receive
spatial information. However, only a minority of neurons relays this
spatial information to the rest of the hippocampus. Thus, granule cells
indeed appear to operate as gatekeepers.

Spatial information processing However, granule cells not only select information but also appear to be involved in information processing. The
team found that the input of the granule cells is broad, but the output
is much more selective. Upstream cortical areas neurons are often grid
cells that generate activity in multiple locations of the environment. In contrast, downstream hippocampal regions neurons are typically place
cells, which fire only at a single location. The new study suggests
that granule cells participate in this conversion. "In simplified terms,
we can think of the granule cell as a unit that translates one neuronal language into another," Jonas explains.

Saving computation power for the future The majority of granule cells
receive spatial information, but only 5% generate spatial output. Xiaomin
Zhang explains: "Especially neurons with a more developed structure
were active, whereas neurons with less mature structure remained
silent." What could be the functional significance of such a unique
design, in which a huge fraction of cells is not directly used for
information processing? The scientists suggested that the hippocampus
reserves most granule cells for future conversion and storage processes.

The new work highlights the power of single-cell recording
techniques. "Our study provides information about the inner workings
of the brain's GPS and the underlying single-neuron computations,"
summarizes Professor Peter Jonas.


========================================================================== Story Source: Materials provided by Institute_of_Science_and_Technology_Austria. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Xiaomin Zhang, Alois Schlo"gl, Peter Jonas. Selective Routing
of Spatial
Information Flow from Input to Output in Hippocampal Granule Cells.

Neuron, 2020; DOI: 10.1016/j.neuron.2020.07.006 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200806111845.htm

--- up 3 weeks, 1 day, 1 hour, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)