Neuroimaging Genomics

by Jason McLeod, MBS 2021, Geisinger Commonwealth School of Medicine

Mentor: Dr. Gregory Shanower, PhD

 

“Click, click, click...” I hear as I am lying in the MRI scanner. It has been about twenty minutes,

and I am getting uncomfortable. “Try not to move. You’re almost there!” the radiology

technologist says through the intercom. It can take anywhere from 15-60 minutes for an MRI,

depending on the body region scanned. It takes a lot longer than a CT scan; however, it

produces a clearer image of various organs and tissues in the body. First, the MRI works by

introducing a magnetic field in and around the scanner. Second, radio waves are introduced,

which cause water molecules in the body to alternate their position briefly. The amount of

energy produced by this action is read by imaging software that has the capability to translate it

into cross-sectional images. These images are generally read by radiologists who interpret the

images in aiding in diagnosing a patient.

 

The MRI is beneficial in understanding one of the most complex organs in our body, the brain.

Not only can an MRI image visualize individual components of the brain, but it can also give an

estimation of overall brain thickness. Variations in brain thickness have become an essential

factor in further understanding complex traits and neurological disorders. Due to the recent

discovery that many traits and neurological disorders have a genetic component, researchers

have decided to investigate if associations exist between genetic variation and brain thickness

in these areas. The method of choice to employ these investigations is the use of MRI imaging.

Brain MRIs of individuals with the neurological disorder Schizophrenia often exhibit some

decrease in overall brain thickness. However, many studies that have been replicated have not

been able to attribute Schizophrenia-associated genetic variation to reductions in overall brain

thickness. Although, many studies examining this relationship have concluded that other areas

of brain structure and volume are different in individuals who do not have Schizophreniaassociated

genetic variation. Another neurological disorder, attention deficit hyperactivity

disorder (ADHD), is often associated with decreased overall brain thickness. Brain MRIs have

also shown a decrease in thickness in areas of the brain, which helps with attention span,

decision making, and memory. This may explain why individuals affected by ADHD can

experience difficulty in paying attention for periods of time. ADHD is also found to be highly

genetic. Brain MRIs have identified decreases in brain structure volume in individuals with

ADHD-associated genetic variation in recent studies. However, when evaluating brain

thickness, these studies often have mixed results.

 

The current research findings are exciting and add to the hope that individuals affected by

neurological disorders will be provided with better treatment options and know their risk of

developing a disease earlier than ever before. However, genetics is not the only component in

complex traits or neurological disorders. Environment plays a significant factor in many cases,

such in the case of intelligence. Intelligence, summarized, is the ability to learn, comprehend,

and problem solve. Due to the complex nature of intelligence, it is mediated by both genetics

and the environment. This does not guarantee that highly intelligent parents will give birth to a

highly intelligent child. It supports the notion that highly intelligent parents will foster an

environment that promotes the accumulation of intelligence factors. Recent studies have

concluded that higher intelligence is shown to be associated with an increase in overall brain

thickness through brain MRI. Yes, that means that highly intelligent people generally have larger

brains. However, it is not as simple as that. Many factors can affect brain thickness. Smoking,

medication use, and even aging alone causes brain thickness to decrease over time. Many

studies have found ways to attempt to counteract these factors, but what about the unknown?

The field of neuroimaging genomics is still very recent. Future considerations for research in

neuroimaging genomics are to try and identify if genetic variation is causing alterations in brain

structure or if disorders developed are mediating these changes. One must consider that the

MRI is only a single snapshot in time. Although cost is a concern, studies would benefit from

examining the long-term changes in study participants through, possibly yearly, brain MRIs.