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 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.”
Source: https://myfusimotors.com/2020/08/05/little-brain-or-cerebellum-not-so-little-after-all/
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