Functional MRI for Major Depressive Disorder
When they hear the word MRI, most people think of the clinical scans commonly used for torn and strained muscles. They aren’t wrong, but these aren’t the only type of MRI scans, and MRI can be used for so much more than temporary injuries. In fact, recent studies suggest that they could be the future of precision medicine and psychiatry for brain based disorders. A special kind of MRI imaging called functional MRI (fMRI) holds great promise for psychiatric disorders, especially Major Depressive Disorder. Wide scale implementation of this could lead to better quality of life for the millions who face this condition every day.
- What is MRI Imaging?
- What is fMRI imaging and how is it different from anatomical MRI?
- How is it used for psychiatric disorders?
- What is Major Depressive Disorder and how does it apply here specifically?
- What are some concerns?
- Conclusion/Key Takeaways
- Further Reading/Sources I Found Helpful
What is MRI imaging?
Magnetic Resonance Imaging (MRI) is a non invasive medical imaging technique that uses strong magnets and radio waves in order to create detailed images of the body. It is frequently used by doctors to make diagnoses or to measure how patients are responding to a treatment. MRIs are similar to x-rays in that they’re body scans used to help assess injury, but unlike x-rays they’re not just for bone damage and do not use any ionizing radiation that can be harmful and have long term implications.
How does it work?
MRI scans are conducted using special scanners. First, the scanner uses magnetic fields and radio waves to measure how much water there is in different tissues throughout the body. From here, it maps out all of the water based on its location in the body, and produces an image. Since the human body is 60–65% water, there are many signals to measure and the images tend to be very detailed.
These images are useful for all over the body, but especially for soft tissues and the nervous system. MRI scans can be used to detect blood vessel damage, blocked blood vessels, stroke, cancer, heart disease, bone infections, joint damage, and poor health in a variety of organs. However, since MRI uses very strong magnets, people with any sort of metal implant or metal on their body that can’t be easily removed cannot get MRI scans. In addition, MRIs are not a good fit for people who are sensitive to noise, claustrophobic, or pregnant.
What is fMRI imaging, and how is it different from anatomical MRI?
The classic type of MRI discussed above is called an anatomical MRI. This is typically what someone is referring to if they use the exact term MRI and do not explicitly say they mean otherwise. However, this isn’t to say that anatomical MRIs are the main type of MRI or even the most popular. One of the most popular subtypes of MRIs are functional MRIs, also known as fMRIs.
Functional MRIs are a special kind of MRI specifically for mapping brain activity. They’re different from anatomical MRI scans because instead of measuring water, they look at blood flow. This is helpful specifically when looking at the brain because physicians and scientists can see how much blood and oxygen is flowing to each part of the brain and therefore get an idea of which areas of the brain are most active in different people. This technique is called BOLD (Blood Oxygen Level Dependent) contrast imaging.
There are two types of fMRIs: task based and resting state. Task based MRIs are taken while the patient performs a series of tasks that can target different brain regions, while resting state (rs-fMRIs) are taken when the person isn’t performing any specific tasks. Task based fMRIs are typically used if trying to examine specific regions of the brain and their stimuli, while resting state are used to look at the brain’s natural blood flow without provocation.
How is fMRI used for psychiatric disorders?
In addition to being useful for information on strokes or surgeries, functional MRIs have recently been found to be super helpful for other brain based conditions such as neurodevelopmental and psychiatric disorders. For now, we’re just going to be looking at psychiatric disorders. These are conditions that involve disturbances in mood or behavior such as Major Depressive Disorder, Generalized Anxiety Disorder, and Schizophrenia.
People with psychiatric disorders have atypical connectome hierarchies, meaning different parts of their brain have more or less connectivity than the average brain. By taking fMRI scans and using BOLD imaging to analyze blood flow, we can identify abnormally connected areas and interpret what their activity says both about the patient and their condition as a whole.
People with psychiatric disorders have very different connectivity from people without, and fMRI data is an important tool for understanding this. The information extracted from fMRI scans can help us see which parts of the brain have abnormal activity levels and attach this back to root causes as well as the effects it has on the patient’s mood or behavior. From here, we are able to improve diagnosis and treatment for each condition and make treatments more personalized. There’s a whole field focused on this, both with clinical and psychiatric regards. These two fields are called precision medicine and precision psychiatry.
FMRI imaging and analysis can lead the way to better understanding and treatment of many different psychiatric disorders. This method has led to interesting studies for a variety of psychiatric conditions, but today we’re going to zoom in on Major Depressive Disorder specifically, as it’s one of the most common psychiatric disorders and affects millions of people.
What is Major Depressive Disorder and how does it apply here specifically?
Major Depressive Disorder (MDD) is a mood based psychiatric disorder that leads to loss of pleasure or interest in activities and less enjoyment of daily life. It’s one of the most common mental health disorders, with over 264 million people estimated to have this condition. The World Health Organization (WHO) credits Major Depressive Disorder to have the greatest proportion of burden associated with non-fatal health outcomes. Note that MDD is classified as unipolar depression and is not to be confused with bipolar disorder, which is a different depressive disorder.
In order to advance precision medicine and psychiatry for MDD and make it easier to identify and diagnose (as is true with many other medical conditions), scientists look for biological markers in the brain known as biomarkers. These are measurable indicators of the presence and severity of a condition. Finding certain biomarkers in someone with Major Depressive Disorder can yield a lot of information on what parts of the brain the disorder is most active in, and this helps physicians see which depressive symptoms are most severe for each patient therefore bringing in the precision aspect.
The reason this is significant specifically for Major Depressive Disorder is that it’s a very heterogeneous condition, meaning that the people with this condition differ a lot from one another in their individual conditions and symptoms. This can create challenges when trying to form treatments based solely on our knowledge of the condition overall because the efficacy will be very inconsistent. Some suggest that MDD should be divided into smaller subgroups that are more homogeneous so that treatments for each will be more consistent, but a lot of work and research would be required for an idea such as this one to be widely accepted and clinically implemented.
For now, using fMRI data to make personalized treatment plans based on resources that are widely available is a great strategy, which is why the use of functional MRI is so important for patients with unipolar depression.
What are some concerns?
Although using fMRI and BOLD for advances in MDD shows great promise for advances in the field, there are certainly concerns (as there almost always are). Even for the best ideas it’s always important to consider potential setbacks, so for the sake of transparency here are some of the top concerns I’ve encountered:
BOLD Technique to Convey Activity
As you’ve now learned, the BOLD technique is used to examine activity in the brain based on the levels of blood and oxygen that flow to each part of it. The more blood rushing to an area, the more activity in that part of the brain. This is used to attach unusual brain functions or activity levels to specific psychiatric conditions.
However, there are a few problems with this. First off, since there’s a lot more water in the body than there is blood, fMRIs are a lot less detailed than anatomical MRIs which makes this process less precise. Second, these images are delayed by several seconds, which can warp results during task based fMRIs. Finally, we use blood flow as an exact correlation to thoughts and activity, but this isn’t necessarily the case, and the magnitude of a BOLD image cannot convey whether it’s positive or negative, as it’s a non-negative system.
Ethics
As is a concern with many emerging technologies, there are many ethical concerns around availability. In this case, people are concerned about the expenses and medical care needed to have access to an fMRI scanner and physician to interpret them. However, as is the common philosophy with many of these technologies, they will only be able to become less expensive and more accessible in the long run if those who are most fortunate begin to use them now.
Conclusion/Key Takeaways
- Magnetic Resonance Imaging (MRI) is a test that uses strong magnets and radio waves in order to create detailed images of the body. It does this by mapping out all of the water in your body based on its location to produce high quality images.
- Functional MRIs are a special kind of MRI specifically for mapping brain activity. They work differently from anatomical (classical) MRIs because they use BOLD (Blood Oxygen Level Dependent) imaging instead of a water based technique.
- There are two types of fMRIs: task based and resting state. Task based MRIs are taken while someone performs a series of tasks that can target different brain regions, while resting state (rs-fMRI) are taken when the person isn’t performing any specific tasks.
- FMRI images can be very useful for psychiatric and other brain based disorders. People with psychiatric disorders have atypical connectome hierarchies, so using fMRI we can identify abnormally connected areas and interpret what their activity says both about the patient and their disorder.
- The use of fMRI for psychiatric disorders is important because it can lead to advances in precision (personalized) medicine and psychiatry, improving the quality of life for millions.
- Major Depressive Disorder (MDD) is a mood based psychiatric disorder that leads to loss of pleasure or interest in activities and less enjoyment of daily life. FMRI imaging is significant specifically for Major Depressive Disorder because it’s a very heterogeneous condition, meaning that the people who have it differ a lot from each other.
- There are certainly some concerns such as lack of detail in fMRI imaging versus anatomical, warped data for task based fMRI, imprecise concluding methods, and ethical concerns around availability for lower class members of society.
Further Reading/Sources I Found Helpful
https://www.nibib.nih.gov/science-education/science-topics/magnetic-resonance-imaging-mri
https://sci-hub.do/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4693599/
Thanks for reading my article, I hope you enjoyed! My name is Raina Bornstein, I’m 15 years old and I’m passionate about neuroscience and brain based disorders. I’d love to connect on LinkedIn, or you can reach out to me at rainabornstein@gmail.com to talk or collaborate. I can’t wait to hear from you!
