'Little brain' or cerebellum not so little after all

Date:
July 31, 2020
Source:
San Diego State University
Summary:
When we say someone has a quick mind, it may be in part thanks
to our expanded cerebellum that distinguishes human brains from
those of macaque monkeys, for example. High-res imaging shows the
cerebellum is 80% of the area of the cortex, indicating it has
grown as human behavior and cognition evolved.



FULL STORY ==========================================================================
When we say someone has a quick mind, it may be in part thanks to our
expanded cerebellum that distinguishes human brains from those of macaque monkeys, for example.


========================================================================== Sometimes referred to by its Latin translation as the '"little brain"',
the cerebellum is located close to the brainstem and sits under the
cortex in the hindbrain. New research at San Diego State University,
however, calls the "little" terminology into question.

The cerebellum plays a versatile role, contributing to our five senses
as well as pain, movements, thought, and emotion.

It's essentially a flat sheet with the thickness of a crepe, crinkled into hundreds of folds to make it fit into a compact volume about one-eighth
the volume of the cerebral cortex. For this reason, the surface area of
the cerebellum was thought to be considerably smaller than that of the
cerebral cortex.

By using an ultra-high-field 9.4 Tesla MRI machine to scan the brain and
custom software to process the resulting images, an SDSU neuroimaging
expert discovered the tightly packed folds actually contain a surface
area equal to 80% of the cerebral cortex's surface area. In comparison,
the macaque's cerebellum is about 30% the size of its cortex.

"The fact that it has such a large surface area speaks to the evolution
of distinctively human behaviors and cognition," said Martin Sereno,
psychology professor, cognitive neuroscientist and director of the SDSU
MRI Imaging Center. "It has expanded so much that the folding patterns
are very complex." Unprecedented insights


========================================================================== Collaborating with imaging and cerebellum experts from the United
Kingdom, Netherlands and Canada, Sereno used customized open source
FreeSurfer software that he originally developed with colleagues while
at the University of California San Diego to computationally reconstruct
the folded surface of the cerebellum. The software also unfolds and
flattens the cerebellar cortex so as to visualize it to the level of
each individual folia -- or thin leaf like fold.

A pioneer in brain imaging who has leveraged functional MRI to uncover
visual maps in the brain, Sereno found that when the cerebellum is
completely unfolded, it forms a strange "crepe" four inches wide by
three feet long. The findings were published this week in a study in PNAS (Proceedings of the National Academy of Sciences).

"Until now we only had crude models of what it looked like," Sereno
said. "We now have a complete map or surface representation of the
cerebellum, much like cities, counties, and states." Puzzle pieces
Previous research discovered that while there were many similarities
between the cortex and the cerebellum, there was one key difference. In
the cerebral cortex, regions representing different parts of the body
are arranged roughly like they are in the actual body: juxtaposed and
orderly. But in the cerebellum, they were placed more randomly.



==========================================================================
"You get a little chunk of the lip, next to a chunk of the shoulder or
face, like jumbled puzzle pieces," Sereno explained.

Those parts of the cerebellum are therefore set up to pull in and
coordinate information from disparate parts of the body.

It is intriguing to think that there might be analogs of '"fractured somatotopy"' in the cognitive parts of the cerebellum that could help
support highly complex, sophisticated cognitive functions, such as
language or abstract reasoning, Sereno said.

"When you think of the cognition required to write a scientific paper or explain a concept, you have to pull in information from many different
sources.

And that's just how the cerebellum is set up." Until now, the cerebellum
was thought to be involved mainly in basic functions like movement, but
its expansion over time and its new inputs from cortical areas involved
in cognition suggest that it can also process advanced concepts like mathematical equations.

"Now that we have the first high resolution base map of the human
cerebellum, there are many possibilities for researchers to start
filling in what is certain to be a complex quilt of inputs, from many
different parts of the cerebral cortex in more detail than ever before,"
Sereno said.

For instance, there is some recent evidence that people who suffer
cerebellum damage have difficulty processing emotion.

"The 'little brain' is quite the jack of all trades," Sereno
said. "Mapping the cerebellum will be an interesting new frontier for
the next decade."

========================================================================== Story Source: Materials provided by San_Diego_State_University. Original written by Padma Nagappan. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Martin I. Sereno, Jo"rn Diedrichsen, Mohamed Tachrount, Guilherme
Testa-
Silva, Helen d'Arceuil, Chris De Zeeuw. The human cerebellum has
almost 80% of the surface area of the neocortex. Proceedings
of the National Academy of Sciences, 2020; 202002896 DOI:
10.1073/pnas.2002896117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200731135558.htm

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