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What the fMRI!
The future of understanding the brain is here
Functional MRI, or fMRI, is a special MRI application. Instead of looking at tissue structure and volume, as is done in many medical MRI scans, fMRI uses the same device to look at brain activation.
This is possible because of the magnetic properties of oxygen-rich blood, which have been known since 1936, with modern fMRI technology being established around 1991. Since then, the method has been used in tens of thousands of studies to identify brain areas and mechanisms pertaining to different psychological and perceptual processes.
Importantly, fMRI experiments usually revolve around a task performed by the participant. This could be very simple, like watching a video or moving a finger, or complex, such as problem solving or a gambling task. In either case, fMRI can be used to look for activation patterns.
Most fMRI experiments do this by comparing activity and rest. Imagine lying in an MRI scanner and moving your hand some of the time, but doing nothing at other times. fMRI can then be used to compare blood oxygenation in any part of your brain during movement and rest. The result is a map of the brain with colorful blobs, which represent the location and intensity of neural activation. Crucially, this is not done by measuring neural activity directly (as an EEG does), but by observing the regions of the brain that use up more oxygen during activation than during rest.
This technology is much slower than some other related instruments (such as EEG), but at the same time it is able to produce a picture with high spatial accuracy: no matter where in the brain something is processed, fMRI can pinpoint the relevant activation with a high level of specificity. This becomes particularly useful when trying to understand the interplay between different brain areas as they relate to a specific mental disorder or perceptual process.
Since medical/diagnostic MRI and functional MRI are very similar, diagnostic MRI devices can be upgraded or retrofitted for fMRI research. However, most fMRI research is performed on dedicated research scanners, often with higher magnetic field strengths than medical or hospital scanners. These higher field strengths help discern signal from noise, which can be useful when looking for the small activational differences that occur during experiments. For the participant, this makes almost no difference: usually the device looks the same, and the restrictions and safety precautions are identical or very similar.
Phantom Limbs
One of the earliest landmark fMRI studies (Flor et al., 1995, Nature) looked at the organization of the brain after amputation: after a limb is lost, areas on the cortex that used to process input from that limb can reorganize, which is a natural adaptive process. This particular study found a clear relationship between the extent of this cortical reorganization and the intensity of phantom limb pain. Much later, my own research (Foell et al., 2014, European Journal of Pain) demonstrated that this reorganization goes back after successful treatment, further illuminating the connection between brain activation and phantom limb pain. It is noteworthy that the phenomenon of phantom limbs after amputation has been medically documented for hundreds of years, but only with fMRI was it possible to quantify and study them, and to thus demonstrate that the condition has a physiological underpinning in the brain.
Building on this, there are now numerous studies investigating how phantom limbs and regular limbs are processed in the brain, and how these processes can be redirected or disturbed. An example is the Rubber Hand Illusion, in which one’s perception is manipulated in a way that can create the sensation of a rubber limb belonging to one’s own body. In a landmark 2012 study (Bekrater-Bodmann et al., Brain Research), it was demonstrated that both the perception of this illusion and its brain correlates remain constant over time, suggesting an individual trait that predisposes someone to be more or less susceptible to this phenomenon. This finding provides new leads in the search for mechanisms behind phantom limb pain, hopefully leading to new avenues for diagnostics and treatment in the future.
Depression and Rewards
Several methods have been used to measure the degree to which reward is processed differently in the brains and nervous systems of depression patients when compared to non-depressed controls. In a landmark study combining fMRI and EEG, Foti et al. (2014, NeuroImage) found blunted reactivity in the ventral striatum, a vitally important region for the processing of reward, in participants with depression. This decrease in fMRI activation corresponded to a diminished reward reaction identified using EEG, further supporting the finding. Crucially, however, this difference in reward dysfunction was most pronounced between sub-groups of depression (i.e., depression with or without impaired mood reactivity), rather than being an indicator of depressed vs. non-depressed participants. As such, this study helped identify sub-groups of depression that differ by mechanism, and not as much by outside phenomenology. This also means that these differences have so far not been acknowledged by standard diagnostic systems; it was only by using fMRI (in combination with other psychophysiological methods) that this distinction could be detected. This will likely have beneficial and clinically relevant consequences for depression treatment.
Meet Dr. Jens Foell
Dr. Jens Foell
Dr. Jens Foell has a PhD in Neuropsychology from Heidelberg
University (Germany) and currently works as Associate in Research at
Florida State University. His work focuses on investigating the
interaction between brain and behavior in the context of body
perception, emotion, psychopathy, and personality traits. His major
research interest is in using novel neuroimaging methods to deepen our
understanding of how differences in brain activation and structure lead
to differences in perception and emotion. In his doctoral studies he
used functional magnetic resonance imaging – fMRI- to demonstrate how
neuroplastic processes in the cortex relate to improvements in phantom
limb pain after applying a specific form of therapy. This research has
led to several follow-up publications on phantom limbs, chronic pain
treatment programs utilizing virtual or augmented reality, and the
integration of external objects into the body image. While still
pursuing this line of research, Dr. Foell is now mostly investigating
how the three components of psychopathy (fear, impulsivity, and
callousness) relate to and depend on specific brain mechanisms. This is
done using functional and structural magnetic resonance imaging, both in
traditional as well as in very large available data sets, and using
electroencephalographic data, peripheral psychophysiological data, and
self-report as well as behavioral measures. These methods are combined
into a psychoneurometric approach that aims at improving the
understanding of personality traits and mental illness by integrating
findings from a diverse range of research methods. The overall goal of
this line of research is to produce knowledge that will lead to new
diagnostic measures and new treatment options for chronic pain and for
mental health and behavioral issues
Dr. Foell has been a close friend of co-owner of MRI Buzz –Lubna Baig (Lexie), BSRT (R) (MR) – since 2017- Together, they often participated in Sci-Comm, PhD talks, and/or discussions surrounding Biomedical Sciences / Diagnostic Medicine – on web-based academic platforms and/or #ScienceTwitter.
Around October 2019, Lexie met Dr. Foell at the Society for Neuroscience – SFN’s – 49th Annual Conference held in Chicago and introduced him to her business/ site partner – Matt Rederer BS RT(R)(MR)(CT) MRSO MRSE (MRSC). We; the makers of MRI Buzz, then, requested his collaboration on the fMRI section of our site – a position he was gracious enough to accept and very much enthusiastic about!
With Dr. Foell’s help; aficionados of MR/MR Safety/Diagnostic Medicine, will be able to enhance their understanding of fMRI and its many advantageous applications that can pave the way for next-generation biomedical imaging.
Psychological models
If the investigation of brain mechanisms can help us differentiate between different types of depression that look very similar at the surface, can fMRI also help us understand other psychological mechanisms that we cannot look at otherwise? Some researchers think so. For example, Berman et al. (2006, Social Cognitive and Affective Neuroscience) describe the testing of two competing models of cognitive control. Both posit a central role for an area called anterior cingulate cortex, but they differed in their assumptions on how exactly this area allows us to control our own behavior and learn from our own mistakes. After different groups of researchers ran fMRI experiments to try and answer this question, it now appears that this particular brain area responds to situations in which errors are likely, instead of being a general conflict monitoring region as some had surmised.
While this is a more abstract question than, for example, where on the cortex a phantom limb is processed or how a brain with depression reacts to reward, it nevertheless demonstrates how fMRI as a method can illuminate questions that are usually understood to be “classic” psychological quandaries.Together with other recent technological developments, fMRI has led to a new wave of categorizational systems for psychological and mental health topics. Several large-scale efforts, such as RDoC (Research Domain Criteria, NIMH) or HiTOP (Hierarchical Taxonomy of Psychopathology) have been developed in recent years in an effort to challenge conventional systems of categorization, and enrich the field by including information derived from neuroimaging, psychophysiological, and genetic studies.
These are just some examples for a wide range of studies and experiments that have been performed using fMRI. At the same time, the technology is being developed further, allowing new analytical strategies (such as looking at entire brain networks instead of focusing on specific regions), entirely new experimental paradigms (such as resting-state fMRI, which brings its own promises and challenges), and increasing field strengths which allow for a more finely grained look at the inner workings of the brain.
References
Bekrater-Bodmann, R., Foell, J., Diers, M., & Flor, H. (2012). The perceptual and neuronal stability of the rubber hand illusion across contexts and over time. Brain Research, 1452, 130-139.
Berman, M. G., Jonides, J., & Nee, D. E. (2006). Studying mind and brain with fMRI. Social Cognitive and Affective Neuroscience, 1(2), 158-161.
Flor, H., Elbert, T., Knecht, S., Wienbruch, C., Pantev, C., Birbaumers, N., … & Taub, E. (1995). Phantom-limb pain as a perceptual correlate of cortical reorganization following arm amputation. Nature, 375(6531), 482.
Foell, J., Bekrater‐Bodmann, R., Diers, M., & Flor, H. (2014). Mirror therapy for phantom limb pain: brain changes and the role of body representation. European journal of pain, 18(5), 729-739.
Foti, D., Carlson, J. M., Sauder, C. L., & Proudfit, G. H. (2014). Reward dysfunction in major depression: Multimodal neuroimaging evidence for refining the melancholic phenotype. NeuroImage, 101, 50-58.
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