White matter helps brain learn

[Guest guest]

http://www.the-scientist.com/news/display/55830/

 

Researchers demonstrate a role for the brain's connective tissue in learning a

new task

 

The brain's white matter - generally thought to play second fiddle to the

neurons that make up the grey matter - expands along with nearby grey matter

when a person learns a new task, scientists at Oxford University report.

MRI of a head

Image: Wikipedia CommonsJust as new neurons may be formed during learning,

corresponding new cells in the white matter may be generated as well, said Jan

Scholz, a student in the lab of Heidi Johansen-Berg at Oxford University, at a

San Francisco meeting of the Organization for Human Brain Mapping last month.

" It's the first time that experience-related white matter changes have been

seen, " Scholz told The Scientist.

White matter is often called the wiring of the brain because it connects

individual neuron and groups of neurons together. Whether or not it plays a role

in learning or cognition, though, is something of a mystery. The Oxford work

built on a 2004 Nature paper that showed that cortical grey matter, which

consists largely of neuronal cell bodies, expanded in people learning to juggle.

In the present study, the Oxford team examined the effects of the same task on

the brain's white matter, which comprises connective tissue such as myelin and

axons.

Scholz and Johansen-Berg, from Oxford's Centre for Functional Magnetic Imaging

of the Brain (FMRIB), taught 24 healthy, right-handed volunteers to juggle. They

scanned subjects' brains using diffusion MRI before the six weeks of training,

directly after, and then again after four weeks of abstinence from juggling.

Diffusion MRI measures how water diffuses within a brain structure, for instance

showing how thick myelin in white matter might be.

The researchers observed grey matter " changes in structure " in a part of the

parietal lobe associated with spatial coordination -- a change which Scholz told

The Scientist probably reflects neurogenesis. Myelin in that region also

appeared thicker, which he similarly attributed to myelinogenesis. Those gains

then eroded after four weeks of no juggling. This temporal and spatial

correlation shows that the two tissue types are working in concert.

" People have long thought of grey matter and white matter as independent

structures, but they are clearly actually quite interdependent, " said Adeline

Vanderver, a neurologist and white matter expert at the National Children's

Medical Center in Washington, DC, of the results. " What I think is really

interesting is that clearly the cells are working together. "

She added, though, that whether or not neurogenesis and myelogenesis were at

play was difficult to determine. " You can't say based on the functional imaging

and fractional anisotropy what is going on at a cellular level. "

Silvia Bunge, a neuroscientist at University of California Berkeley, said that

the demonstration of a link between white matter and grey matter is " hugely

important " for the study of learning in humans, especially children. Indeed, her

PhD student Kirstie Whitaker is looking at similar white matter development in

school children.

" White matter is important -- that has been shown over the last 5-10 years. But

it is definitely a new area of investigation. " Whitaker said. " It's exciting to

see a training study where over the course of six weeks they can see changes [in

white matter] and reverse those changes. "

Pinning down the role of white matter may help scientists understand brain

networks. Elucidating the mechanism by which the tissue expands may also provide

clues to treatments for diseases such as multiple sclerosis, which results from

withering of myelin in the central nervous system.

" It's one of these thing that now that you look back on it you say, 'Oh, that

must be happening,' but no one had ever thought of it quite that way, " said

Vanderver of combined white/grey matter growth. " A better understanding of this

interdependency will help us help people's brains. "

Related stories:

Brain's neuronal nexus mapped

[1st July 2008]

Decoding the brain

[July 2007]

Love, Gabby. :0)

http://stemcellforautism.blogspot.com/

 

" I know of nobody who is purely Autistic or purely neurotypical. Even God had

some Autistic moments, which is why the planets all spin. " ~ Jerry Newport