Nav: Home

Illumination of abnormal neuronal activities caused by myelin impairment

October 11, 2019

The neural circuit basis for motor learning tasks when myelination is impaired has been illuminated for the first time by an international collaboration of university research teams. They also succeeded in compensating for the impaired motor learning process by pairing appropriate actions with brain photo-simulation to promote synchronization of neuronal activities. This could contribute to future treatments for neurological and psychiatric diseases in which white matter function is impaired.

The research was carried out by Assistant Professor Daisuke Kato and Professor Hiroaki Wake (Kobe University Graduate School of Medicine, Japan), Professor Junichi Nabekura (National Institute of Physiological Sciences, Japan), Dr. R Douglas Fields (National Institutes of Health, USA) and Professor Masanori Matsuzaki (Tokyo University Graduate School of Medicine, Japan).

The results were first published in the journal 'GLIA'.

Introduction:

Myelin is sheath that forms around axons, regulating the speed of electrical impulses and efficiently transmitting them among the neurons. Myelinated bundles act as cables to connect distant brain regions. Once myelination is impaired or the myelin is damaged, the propagation of impulses in the neurons slows down or is dysregulated. This impaired regulation has been linked to abnormal activity in neuronal populations, resulting in learning deficits and aging (particularly in dementia and Alzheimer's disease). The resulting changes in white matter have been observed in the MRI scans of patients with Alzheimer's. However, it is still poorly understood how exactly impaired myelination affects the circuit properties of the brain that are important for learning and cognition.

This research showed that impaired myelination causes uncoordinated or asynchronous electrical impulse transmission between neurons. Impaired myelination was shown to have an adverse effect on motor learning in mice, suggesting that coordinated transmissions are vital for effective learning.

Research Methodology:

The population activity of neurons in the primary motor cortex of mice with myelin impairments was measured during a motor learning activity usingin vivotwo photon microscopy. Mice with head plates were inserted into body chambers. The mice were trained to pull and hold a lever that would dispense drops of water. Mouse behavior was monitored by infrared video camera. In the early stages of training there was no difference in the performance between myelin impaired mice and control mice. However, in the later stage of training the myelin impaired mice had a lower success rate in performing the task, although the amount of attempts was similar. Although this suggests their motivation levels were the same, the myelin deficit made it more difficult for the mice improve their performance of this task. It also reduced the accuracy of their movements and increased the spontaneous activities of neuronal population.

Through analyzing the activity of the neurons of myelin impaired mice, they showed that asynchronous activity in the thalamocortical axons correlated with impaired task performance. Thalamocortical axons are nerve fibers connecting the thalamus and cerebral cortex of the brain which carry nerve cells' information. Electrical stimulation of the motor cortex (output area) during the lever pull task was utilized to promote synchronous activity of neurons in motor cortex and to try to compensate for the performance of the mice. This promoted synchronous activity in the thalamocortical axons during learning and improved the success rate of the mice with myelin impairment.

Conclusions:

The findings of this research illuminate how pathological neuronal circuit activity is affected by impaired myelination. The results also suggest that it may be possible to pair noninvasive brain simulation with relevant behaviors to correct cognitive and behavioral abnormalities in the early stages of diseases with impaired white matter.
-end-
Glossary:

Thalamocortical axons: are nerve fibers connecting the thalamus and cerebral cortex of the brain which carry nerve cells' information.

Oligodendrocytes: are specialized brain cells responsible for the myelination in the central nervous system. They are vital to neuron survival.

Acknowledgements:

This research was supported by MEXT (Ministry of Education, Culture, Sports, Science and Technology), JST (Japan Science and Technology Agency) and AMED (Japan Agency for Medical Research and Development).

Kobe University

Related Neurons Articles:

How do we get so many different types of neurons in our brain?
SMU (Southern Methodist University) researchers have discovered another layer of complexity in gene expression, which could help explain how we're able to have so many billions of neurons in our brain.
These neurons affect how much you do, or don't, want to eat
University of Arizona researchers have identified a network of neurons that coordinate with other brain regions to influence eating behaviors.
Mood neurons mature during adolescence
Researchers have discovered a mysterious group of neurons in the amygdala -- a key center for emotional processing in the brain -- that stay in an immature, prenatal developmental state throughout childhood.
Astrocytes protect neurons from toxic buildup
Neurons off-load toxic by-products to astrocytes, which process and recycle them.
Connecting neurons in the brain
Leuven researchers uncover new mechanisms of brain development that determine when, where and how strongly distinct brain cells interconnect.
The salt-craving neurons
Pass the potato chips, please! New research discovers neural circuits that regulate craving and satiation for salty tastes.
When neurons are out of shape, antidepressants may not work
Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed medication for major depressive disorder (MDD), yet scientists still do not understand why the treatment does not work in nearly thirty percent of patients with MDD.
Losing neurons can sometimes not be that bad
Current thinking about Alzheimer's disease is that neuronal cell death in the brain is to blame for the cognitive havoc caused by the disease.
Neurons that fire together, don't always wire together
As the adage goes 'neurons that fire together, wire together,' but a new paper published today in Neuron demonstrates that, in addition to response similarity, projection target also constrains local connectivity.
Scientists accidentally reprogram mature mouse GABA neurons into dopaminergic-like neurons
Attempting to make dopamine-producing neurons out of glial cells in mouse brains, a group of researchers instead converted mature inhibitory neurons into dopaminergic cells.
More Neurons News and Neurons Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.