Understanding the Brain and MRI: How a Huge Magnet Affects Electric Impulses

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In summary, the brain uses electric impulses and an MRI uses a huge magnet to create images of the brain's activity. The magnet aligns the axes of spins of the nuclei in the brain's atoms, creating a Nuclear Magnetic Resonance (NMR) which is then translated into a Magnetic Resonance Imaging (MRI) image. Although there have been studies on the effects of magnetic fields on the brain, the total field emitted by an MRI is comparable to a normal permanent magnet and is considered safe. Transcranial Magnetic Stimulation (TMS) is a technique that uses a magnetic field to stimulate specific areas of the brain, which has been studied for various applications such as treating depression and warding off the effects of sleep deprivation.
  • #1
eok20
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I only have a vague idea of how the brain and MRI work but from my understanding the brain uses electric impusles and an MRI uses a huge magnet. Since a magnetic force redirects a moving charge, why doesn't someone go crazy when they are in an MRI because the neurons don't go where they are supposed to?

Thanks.
 
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  • #2
eok20 said:
I only have a vague idea of how the brain and MRI work but from my understanding the brain uses electric impusles and an MRI uses a huge magnet. Since a magnetic force redirects a moving charge, why doesn't someone go crazy when they are in an MRI because the neurons don't go where they are supposed to?

Thanks.
Neurons don't travel in the brain, they are cells that have long "arms" called axons down which electrochemical signals can pass, and the axons end in bulbs which almost touch the bulbs of other neurons across gaps called synapses, and some bulb emit molecules of various kinds and others absorb certain kinds, and the rates at which these synaptic processes happen have a lot to do with our thinking.

Now way down below this chemical, molecular level is the atomic level, and the nuclei of the atoms have spin, and what the magnet does is get the axes of spins of those nuclei lined up. Then when a chemical event happens in a molecule the resulting electrical force will make the spinning nucleus precess like a gyroscope, and according to the laws of electromagnetism it will emit a photon of EM radiation, whose frequency will depend on the rate of precession and hence on the force and hence will encode the strength of that chemical event. And because the axes were all lined up, the signals from different atoms will coordinate. This is called a Nuclear Magnetic Resonance (NMR) and they have software that can read all these resonances from different nuclei and build pictures, which is called Magnetic Resonance Imaging (MRI). And all this jiggling of molecules is otherwise invisible at the molecular level where thinking is generated.
 
  • #3
selfAdjoint pretty much has it.

Although, there have been some studies into the effects of magnetic fields on the brain. Obviously, the MRI NMR guys have done testing to make sure it's safe to go into the scanners.

But I've also heard of at least one group who've tried stimulating bulk areas of brain tissue using a magnetic field projected from what's basically a coil in a plastic paddle thingy.

They noticed some interesting effects when it was positioned over certain areas of the brain; the person's ability to draw might improve for example. Although, these were highly qualitative experiments as you can imagine.

The total field emitted from an MRI is very high, but the actual density of the field is comparable to a normal permanent magnet. And the ionic currents that make neurons work are tiny and quite rough in operation (they work in a digital, all or nothing manner), so they'd seem to need quite a strong field to make a difference (if you think about them in terms of a hall sensor, were you have a current flowing in one direction, a field penetrating that current region like it would in a bubble chamber and then a voltage difference produced on either side of the device as a result of the eletrons' paths bending left or right slightly, the bigger the quiescent current you have the greater the voltage difference you'll see).
 
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  • #4
eeka chu said:
But I've also heard of at least one group who've tried stimulating bulk areas of brain tissue using a magnetic field projected from what's basically a coil in a plastic paddle thingy.

They noticed some interesting effects when it was positioned over certain areas of the brain; the person's ability to draw might improve for example. Although, these were highly qualitative experiments as you can imagine.

It's called Transcranial Magnetic Stimulation (TMS), and is being used tested at a lot of different places for various things. A Pubmed search on Transcranial Magnetic Stimulation will yield plenty of papers on the topic.

Depending on what area it's being used on, it can be called TMS, VNS (Vagal Nerve Stimulation) or DBS (Deep Brain Stimulation), but all are variants of the TMS technique. The most common application being examined is as a potential treatment for depression. Some people at the hospital I work at got some research money from DoD a few years ago to see if it can be used to temporarily ward off the effects of sleep deprivation. The TMS technique can pretty much be used to stimulate any area of the brain more efficiently than electrical methods (i.e. electroconvulsive shock), including the motor cortex.
 
  • #5
imabug said:
Some people at the hospital I work at got some research money from DoD a few years ago to see if it can be used to temporarily ward off the effects of sleep deprivation.

Very, very lame, "can we make it into a gun?"

The only problem with magnetic stimulation is the resolution of the field, which can easily by surpassed by a physical probe touching the brain. But if you wanted to stimulate bulk tissue, no problem.
 

FAQ: Understanding the Brain and MRI: How a Huge Magnet Affects Electric Impulses

What is the purpose of MRI in studying the brain?

MRI, or Magnetic Resonance Imaging, is a powerful tool for studying the brain as it allows for non-invasive and detailed images of the brain's structures and functions. It uses a strong magnetic field to align the atoms in the brain, and then uses radio waves to produce detailed images that can help us understand how the brain works and identify any abnormalities.

How does a huge magnet affect electric impulses in the brain?

A huge magnet, such as the one used in MRI machines, can disrupt the electric impulses in the brain by creating a strong magnetic field that can interfere with the normal functioning of neurons. This can lead to temporary changes in brain activity, but research has shown that it does not cause any long-term damage to the brain.

What are the benefits of using MRI over other brain imaging techniques?

MRI has several advantages over other brain imaging techniques, such as CT scans or PET scans. It provides more detailed images, has better contrast resolution, and does not use any harmful radiation. It also allows us to study the brain's structure and function simultaneously, providing a more comprehensive understanding of the brain.

Are there any risks associated with MRI scans?

MRI scans are generally considered safe and do not have any known risks associated with them. However, individuals with certain medical devices, such as pacemakers or metal implants, may not be able to undergo an MRI scan due to the strong magnetic field. It is important to inform the MRI technician of any medical conditions or devices before undergoing the scan.

How can MRI help in diagnosing brain disorders?

MRI scans can be used to diagnose a variety of brain disorders, such as tumors, strokes, and neurodegenerative diseases. The detailed images produced by MRI can help doctors identify any abnormalities in the brain's structure or function, allowing for early detection and treatment of these disorders. MRI can also be used to track the progression of diseases and monitor the effectiveness of treatments.

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