New research on brain and neuro plasticity

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More research that supports the neuro plasticity at any age...by learning!

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Brain change

Posted In: Life Sciences

By ResearchSEA

Sunday, February 7, 2010

Cutting-edge imaging technology shows that monkeys' brains grow as they learn to

use tools

Macaque monkeys rarely use tools in the wild, but they can be taught, and it

appears that their brains change in response to these new tasks.

Copyright : istockphoto.com/cameranew

Many scientists once believed that the human brain doesn't change significantly

after a person reaches maturity. This opinion has been overturned in the last

few decades as studies have revealed that the brain has a very flexible

structure, even in adulthood, and changes considerably according to use.

Now, Atsushi Iriki at the RIKEN Brain Science Institute (BSI) in Wako and

colleagues have directly observed changes in the brain structure of macaque

monkeys, while the monkeys were being taught to use tools1. The study, performed

using a non-invasive imaging technique, is the first to reveal significant

changes in the brain of an individual animal, and could provide insight into the

evolution of human intelligence.

Growth through learning

Several research groups have measured changes in human brain structure by

analyzing the brains of experts in a particular field and comparing them to

non-experts. This work has revealed, for example, that London taxi drivers, who

have to remember a huge network of streets, display enhanced growth in the

hippocampus region associated with spatial memory, and expert musicians have

larger auditory and motor cortices thanks to their years of practice.

Iriki was particularly inspired by a study conducted by German scientists in

2004, in which human volunteers were trained to juggle over a three-month

period. After the training, the volunteers showed increased gray matter in

regions of the brain associated with motor skills. Iriki was keen to discover

whether these effects could be observed in macaque monkeys.

" In our previous work, we found that neurons in the intraparietal cortex of

monkeys trained to use tools change their receptive field properties to

represent tools as an extension of the body parts holding them, " he explains.

Iriki and his colleagues observed gene expression in the same areas, and the

growth of new axons and synapses. This suggests that tool-use training might

induce rapid structural changes in the brain, at least on a microscopic scale.

" So, when I read the paper describing expansion of cortical gray matter in

jugglers, I decided to do a similar study in monkeys, " says Iriki.

Scanning in stages

Macaque monkeys rarely use tools in the wild, but can master basic tools after a

few weeks training. To gain insight into this learning process the researchers

used magnetic resonance imaging (MRI) to examine the brains of three monkeys

before, during, and after training them to use a rake to retrieve food that was

just out of reach.

The researchers used a technique called voxel-based morphometry (VBM) to

classify areas of brain tissue in their MRI images as grey matter, white matter,

or cerebro-spinal fluid, and to compare the volume of each tissue at different

stages of learning. The work was possible thanks to a fruitful collaboration

between RIKEN BSI and the Institute of Neurology at University College London

(UCL).

" Marsha Quallo, a PhD student from UCL, came to BSI to train the monkeys

and analyze behavioral data, during which time she acquired structural MRI

images using our high resolution scanner, " explains Iriki. " She took the MRI

data back to London and analyzed them under supervision of VBM experts there. "

The analysis showed that the MRI signal from some areas of gray matter

increased, suggesting their volume in the monkey's brains increased as the

monkeys got better at using the tool. The growth was mainly in areas around the

superior temporal sulcus (STS), intraparietal sulcus (IPS), and the secondary

somatosensory area (SII) which all belong to a network previously associated

with tool use. The researchers also noticed an increase in signals, suggesting

volume expansion, from white matter in the cerebellum, which is well known as

having a role in motor control.

The benefit of monkey models

The study is important because it is the first to detect statistically

significant brain structure changes in individual animals, compared to human

studies that pooled data from several people.

" Although there have been some human VBM studies suggesting gray matter

expansions in experts, they could only be detected in group analyses by

comparing between groups of experts and non-experts, " Iriki explains. " In

contrast, we detected large changes in specific brain regions by using animals

that were naïve to the task, and showed for the first time that these can be

detected in individual animals. "

For example, the juggling study reported only a 3% increase in signals averaged

across twelve volunteers, whereas the individual macaques in Iriki's study

showed up to 17% signal increase in some areas. The changes may be larger in the

monkeys because they had never used tools, unlike humans who would have already

performed many skilled motor tasks. This illustrates that monkeys are an ideal

model for studying such brain changes.

Looking deeper

Iriki and colleagues now hope to discover exactly how different brain areas

increase in volume when learning a task, on a cellular, genetic and molecular

basis.

" Our study opens up the means to study concrete neurobiological mechanisms

underlying gray matter expansion, which we have actually already started, " says

Iriki. " We are particularly keen, in collaboration with other groups in Japan,

on using marmosets—smaller primates in which transgenic techniques are

available. "

Most interestingly, Iriki points out that the brain areas highlighted in his

study correspond closely to the cortical areas that expanded most while primates

were evolving into humans.

" I would hope this could give us some clues to understanding human intellectual

evolution, " he says.

About the Researcher

Atsushi Iriki

Atsushi Iriki received his Ph.D. in Neurophysiology from Tokyo Medical and

Dental University in 1986. He held research associate positions at the Tokyo

Medical and Dental University and then at the Rockefeller University. He joined

the faculty of Toho University Medical School as an assistant professor and as

an associate professor in Physiology (1991-1999). In 1999, he returned to Tokyo

Medical and Dental University as a full professor in Cognitive Neurobiology.

Atsushi Iriki is now a Head of Laboratory for Symbolic Cognitive Development at

RIKEN Brain Science Institute since 2004. He is an adjunct professor of Tokyo

Medical and Dental University, The University of Tokyo, Keio University, and a

visiting senior fellow of University College London. Based on behavioral and

neurophysiological analyses on chronic macaque monkeys, which were trained to

use tools and other high-tech apparatus, he tries to uncover evolutionary

precursors of human higher cognitive functions grounded onto physical

morphologies and patterns of structured bodily actions. He extrapolates these

mechanisms to constitute bases of communicatory functions by sharing above

machineries among individuals, and eventually understand neural mechanism of

social behaviors. Further, he is aiming at extending these mechanisms onto

evolutionary as well as developmental clues of symbolic cognitive functions to

subserve inference, metaphysical thoughts etc. that characterise human

intelligence.

Atsushi Iriki

Copyright : RIKEN 2010

Journal information

1. Quallo, M.M., Price, C.J., Ueno, K., Asamizuya, T., Cheng, K., Lemon, R.N. &

Iriki, A. Gray and white matter changes associated with tool-use learning in

macaque monkeys. Proceedings of the National Academy of Sciences USA 106,

18379–18384 (2009).

2. Draganski, B., Gaser, C., Busch, V., Schuierer, G., Bogdahn, U. & May, A.

Neuroplasticity: Changes in grey matter induced by training. Nature 427, 311–312

(2004).

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