Brain remapping dysfunction causes spatial memory impairment in
Alzheimer's disease
A step towards a treatment of wandering behaviors in dementia patients


Date:
August 19, 2020
Source:
Japan Science and Technology Agency
Summary:
A research group elucidated the brain circuit mechanism that cause
of spatial memory impairment in Alzheimer's disease. In the future,
improving brain remapping function may reverse spatial memory
impairment in patients with Alzheimer's disease.



FULL STORY ========================================================================== Alzheimer's disease is one of the most serious diseases in an aging
society, yet the cause is often unclear and there is no appropriate
treatment method.

Many patients with Alzheimer's disease develop spatial memory impairment
which causes symptoms such as wandering, putting a great stress on
caregivers.

However, the cause of spatial memory impairment has been long unclear.


==========================================================================
A research group led by Kei Igarashi, an assistant professor at University
of California, Irvine elucidated the brain circuit mechanism that cause
of spatial memory impairment in Alzheimer's disease. The research group
used Alzheimer's disease model mice developed at RIKEN in 2014 and
analyzed the brain activity of mice performing memory behaviors using
an electrophysiological technique(1).

The results showed that brain function to distinguish different locations called as "remapping"(2), a function of the hippocampus(3) of healthy
brain, become impaired. The results also showed that this hippocampal dysfunction was caused by decreased activity in the brain region called
the entorhinal cortex (4).

These results indicate that the impairment of remapping causes spatial
memory impairment in Alzheimer's disease. In the future, improving brain remapping function may reverse spatial memory impairment in patients with Alzheimer's disease, for example using deep brain stimulation methods.

The study was conducted jointly with Takaomi Saido, a team leader at the
RIKEN and Professor Takashi Saito at Nagoya City University, as part of
the JST Strategic Basic Research Programs.

(1) Electrophysiological technique This is a method for directly measuring electrical signals using metal electrodes for recording brain activity.

(2) Remapping The function of place cells and grid cells to distinguish different rooms.

Since there are countless place cells in the hippocampus, every time
an animal moves into a different room, activity patterns of many place
cells will change all at once. Since the combination of place cell group patterns is different in each room, combinations of place cells create
spatial memory of different locations.

(3) Hippocampus The memory center of the brain. The hippocampus, the Greek
word for seahorse, is so named because it has a shape similar to that of
a seahorse. It has special electric circuits to store and recall memory information. When the hippocampus is damaged, memory impairment occurs.

(4) Entorhinal cortex A part of the brain that forms the memory center
of the brain along with the hippocampus. Information from various parts
of the brain enters the hippocampus through the entorhinal cortex and is
stored in memory. The information stored in the hippocampus is transferred
to various parts of the brain through the entorhinal cortex. Therefore,
damage to the entorhinal cortex also causes memory impairment.


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


========================================================================== Journal Reference:
1. Heechul Jun, Allen Bramian, Shogo Soma, Takashi Saito, Takaomi
C. Saido,
Kei M. Igarashi. Disrupted Place Cell Remapping and Impaired Grid
Cells in a Knockin Model of Alzheimer's Disease. Neuron, 2020;
DOI: 10.1016/ j.neuron.2020.06.023 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200819094750.htm

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