| Paper authors: | Ruiyang Ge, Jonathan Downar, Daniel M. Blumberger, Zafiris J. Daskalakis, Fidel Vila-Rodriguez |
| Year of paper publication: | 2019 |
| Post authors: | Caleb Pozdnikoff, Lisa Ridgway, Fidel Vila-Rodriguez |
| Download the research article: | Ge (2019) Functional connectivity of the anterior cingulate cortex predicts treatment outcome for rTMS in treatment-resistant depression at 3-month follow-up |
Introduction
When a doctor recommends you try a treatment for depression, wouldn’t it be nice if they could gauge whether or not you will respond to treatment before even starting?
In this study, researchers look at this idea and propose a possible measurement that may be able to predict if an individual will positively respond to repetitive transcranial magnetic stimulation (rTMS) treatment. rTMS is a safe, non-invasive technique used to treat depression. It works by applying a coil to the scalp, which then delivers magnetic pulses that disrupts the way the brain functions in a patient with depression.
As mentioned in several of our recent articles, the measurement the researchers looked at to predict treatment response were the changes in brain function (activity) in a specific part of the brain that rTMS affects, the anterior cingulate cortex (ACC). Different areas of our brain are always in “conversation” – coordinating their activity in order to do everything from seeing, talking, breathing, and even dreaming! Areas of our brain that change levels of activity at the same time (i.e., are coordinated) are said to have “functional connectivity”.
This study aimed to explore whether the functional connectivity of different parts of the ACC might serve as potential predictors for treatment response, and whether improvement in depression after rTMS is associated with any changes in functional connectivity in these areas.
Methods
This study included 50 people with moderate or severe treatment-resistant depression. There were also 42 “healthy controls” This study included 50 people with treatment-resistant depression (TRD). This means they had to have tried, and not benefited from, at least one antidepressant in the past. There were also 24 “healthy controls” (people without depression or other illnesses) that were used as a comparison group.
Just like in our other recent articles, brain activity was measured using functional magnetic resonance imaging (fMRI). To take these images, each patient lies down in a tube-like scanner. This scanner uses very strong magnets and tracks how different molecules in the brain react to it. Areas of our brain that are very active use a lot of blood and oxygen for energy, when compared to areas of our brain that are not active. The fMRI detects these differences in blood and oxygen to determine what brain areas are working at any given time. For an additional video that explains how MRIs and fMRIs work, check out this link: https://youtu.be/4UOeBM5BwdY?si=qVcXgGJy2kDmiqSj.
Brain activity was measured 1 week before starting rTMS, and 3 months after finishing rTMS.
There were 4 areas of the brain the researchers were primarily interested in:
- The dorsolateral prefrontal cortex (DLPFC) is where the rTMS was administered, and it is linked to modulating emotion
- The subgenual anterior cingulate cortex (sgACC) is thought to help with our decision-making and emotion regulation
- The rostral anterior cingulate cortex (rACC) is activated when people are at rest and letting their mind wander
- The lateral parietal cortex (IPL) is involved in the Default Mode Network, a series of brain regions that are activated when the brain is at rest (during daydreaming or self-reflecting)
- To see the locations of these regions, refer to the image at the top of this page
First, the individuals in the study with depression received an fMRI 1 week before starting the rTMS treatment. Next, they received high frequency rTMS every weekday for 4-6 weeks (20-30 treatments total). Lastly, 3 months after the treatment ended, they received another fMRI scan that the researchers used to compare to their first scan and to the control group’s scans.vations.
Results
- The researchers found that rTMS treatment was associated with changes in brain function immediately after treatment, as well as three months after completing treatment.
- These brain function changes were associated with changes in depressive symptoms
- Higher levels of functional connectivity between the sgACC and the DLPFC was associated with less improvement of depressive symptoms after treatment was finished
- The researchers used this finding to predict who would respond to the treatment and who would not respond
- Higher levels of functional connectivity between the rACC and the IPL was associated with greater improvement in depressive symptoms
Conclusion
This study found that using patterns of brain activity in people with depression seems to be a useful tool in predicting if people will respond to high frequency rTMS treatment. Specifically, more coordinated activity between the sgACC and the DLPFC appears to be associated with less likelihood of rTMS being effective in people with TRD, while more coordinated activity between the rACC and the IPL seems to be associated with a higher likelihood of rTMS being effective.
Predicting who might benefit best from rTMS is an important topic for researchers: it can help direct patients and clinicians to whatever treatments would be best for them. This study is a step toward this goal, but more research is needed before we can have a complete understanding of how we can predict, and ultimately prescribe, what treatment is best for a specific individual.