Mice's learning skills help researchers pinpointing brain areas where
acquired knowledge is stored

Date:
September 21, 2021
Source:
Max-Planck-Gesellschaft
Summary:
Is it a Rembrandt or a Vermeer? For lay people, it is often
challenging to distinguish paintings by these two old masters. For
the trained eye of an expert, on the other hand, it is not difficult
at all. Scientists have now demonstrated that mice can also become
experts in sorting images into categories. The study shows that
part of the category knowledge is already present in early visual
areas, highlighting how widespread such semantic memories are
stored throughout the brain.



FULL STORY ==========================================================================
Is it a Rembrandt or a Vermeer? For lay people, it is often challenging
to distinguish paintings by these two old masters. For the trained eye
of an expert, on the other hand, it is not difficult at all. Scientists
at the Max Planck Institute of Neurobiology have now demonstrated that
mice can also become experts in sorting images into categories. The
study shows that part of the category knowledge is already present in
early visual areas, highlighting how widespread such semantic memories
are stored throughout the brain.


==========================================================================
Have you ever tried to distinguish a painting by Rembrandt from one by
Vermeer? It could certainly seem like a guessing game: the differences
are subtle to an untrained eye. An art enthusiast, however, has no problem
with the classification -- even though there are few clues that can be generally applied. How is that possible? Semantic memory is a store
for expert knowledge One key to success is practice. Art experts look
at hundreds of paintings day in and day out. They gradually develop a
sense of the features playing a role in the discrimination. This sense
is nothing but acquired knowledge, which is stored in their semantic
memory. This type of memory contains all abstract information that is
not linked to a specific experience: for example, the general fact that
Vermeer is a Dutch painter -- in contrast to the exact memory of where
they first saw a Vermeer painting.

To date, however, we know little about how semantic memory is stored in
the brain. Pieter Goltstein, neurobiologist working with Mark Hu"bener in Tobias Bonhoeffer's department, explains: "To study how such information
is stored, we first need to know where to find it in the brain. We came
up with the idea to give mice a task similar to those of art experts, and
test if the animals can also acquire such complex knowledge." Mice become experts at categorizing Together with Sandra Reinert, Pieter Goltstein
showed mice different pictures of stripe patterns, which they had to
sort into two categories. To do so, the animals had to weigh different
aspects of the stripes and include both their width and their orientation.



========================================================================== Surprisingly, after an initial learning phase, the mice had no trouble
in sorting the patterns into the correct category. They had become
experts and could readily apply their newly learned category knowledge
to patterns that they had not seen during learning yet -- extrapolating
from the category features that they had stored as semantic information.

The visual cortex helps to categorize But is the category information
already stored in the visual cortex, where visual stimuli arrive and are represented? Or is it only found after many initial processing steps,
in some higher brain area? The scientists used a little trick to answer
this question: Since neurons in the visual cortex react to visual stimuli
in a particular location, they initially trained the mice using stripe
patterns shown only in a part of their visual field. In this way,
only a specific group of neurons were trained in these animals. When
the researchers then shifted the patterns to another location, and
therefore stimuli were processed by different neurons, the mice could
not categorize as well anymore. Inactivating the visual cortex led to a
similar outcome. Together, these results indicated that neurons in the
visual cortex are involved in the task of category learning.

Signatures of semantic memories are already found in the visual cortex In parallel to the category training, the scientists were able to repeatedly measure the activity of many neurons and identify changes over the course
of learning. Interestingly, toward the end of the learning process,
some regions of the visual cortex became better in distinguishing
categories. Mark Hu"bener, senior author of the study, explains: "The
neurons in these regions receive two kinds of input. They respond to
a specific visual stimulus, and they also receive information when the
mouse sorts an image into the correct category.

This allows the neurons to identify important visual stimuli related to categories, and enhance their reaction to them." Neurons in the visual
cortex are thus able to adapt their response during learning. But not
only that: Analyzing the data, a region of the visual cortex, called
POR, stood out in particular. There, the researchers found signs of
stored abstract category information. The study thereby tracks down that abstract learning already begins at the first levels of visual processing.

========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Pieter M. Goltstein, Sandra Reinert, Tobias Bonhoeffer, Mark
Hu"bener.

Mouse visual cortex areas represent perceptual and semantic
features of learned visual categories. Nature Neuroscience, 2021;
DOI: 10.1038/ s41593-021-00914-5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210921125127.htm

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