Illumination of abnormal neuronal activities caused by myelin impairment

Posted on October 23, 2019

Myelin acts as a 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 destroyed, the propagation of impulses in the neurons slows down or is dysregulated.

This impaired regulation is linked to abnormal activity in neuronal populations, resulting in learning deficits and aging (particularly dementia and Alzheimer’s diseases). The resulting change 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 shows that impaired myelination causes uncoordinated electrical impulse transmission between neurons. Impaired myelination was shown to have adverse effect on motor learning in mice, suggesting that coordinated transmissions are vital for effective learning.

Through analysing the activities 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.

Findings illuminated how pathological neuronal circuit activity is affected by impaired myelination. This suggests that it may be possible to pair noninvasive brain simulation with relevant behavior to correct cognitive and behavioral abnormalities in the early stages of diseases with impaired white matter.

Source material from Science Daily

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