A Closer Look at fMRI Photographs
Over the years our field has seen several addiction models come and go. Way back it was the moral concept, then the disease model, and now we seem to be in the burgeoning neuroscience era. These days you can’t pick up a reputable addiction journal—Alcohol Research, for example—without an article touting some new addiction brain discovery. And the go-to instrument for such discoveries is the vaulted magnetic resonance imaging (MRI) machine and the accompanying colorful scans.
There has been some criticism leveled at MRIs; you should be mindful of them. The central point of the criticism is not to read too much into what is being implied by MRI scans, at least not yet.
How Do MRIs Work, Anyway?
To get a handle on MRI scans, you need to ask an important question: What I am I really looking at? That means acquiring a rudimentary understanding of how magnetic resonance imaging works. Essentially, an individual is placed in a narrow cylinder that contains two large magnetic coils. When these coils are turned on, it creates a very powerful magnetic field and aligns the atoms in the body in one direction, much like a compass. In this process, a small radio pulse from the atoms is generated. When the atoms return to their original state they again emit a small pulse of energy, the MRI machine reads both pulses. It is like reading an echo that can locate the atoms in the body. Computers then reconstruct these echoes and we get that brain image we have all seen (Kaku, 2014). This atom flipping is technically called “magnetic resonance.” Scientists have known about it for decades (Watson, 2008).
In the 1990s, a new type of resonance was developed. It was called “function magnetic resonance imaging” of the now familiar initials fMRI. A lowercase letter in front of the MRI designates a different type of machine, in this case “functional.” The improvement in the fMRI was that it could read oxygen in the blood stream—so, it can read the difference between oxygen rich blood coming from the heart and oxygen poor blood leaving the brain. They have different magnetic resonances. The fMRI picture you see is really an image of increased blood flow, which indicates greater brain activity. The improved machine does all this imaging with a fair amount of accuracy, and can generate a three-dimensional image (Kaku, 2014; Watson, 2008).
While these are amazing machines and add to the wealth of knowledge in our field, we need to be a little careful of getting spellbound and glassy-eyed, because a few limitations are in order.
Some Problems With fMRI
Most of us marvel at this amazing machine, and therein lies some of its general problems. Those problems, in turn, create problems for fMRI general psychology and addiction explanations.
One sizeable issue is that scientists will tell you that they cannot simply look at a brain image and tell you the thoughts and feelings merely from the scan. Those striking color fMRI images are just a representation of particular brain areas that are working harder, as measured by increased oxygen consumption. You see it for example when a subject performs a task, ingests a substance or reacts to a stimulus (Shermer, 2008; Satel, 2013). The big point is that it is very difficult for the scientific community to look at a brain scan hot spot and determine with certainty what is going on in the mind of the subject (Satel & Lilienfeld, 2015).
Another snag is that a hot spot you see in the fMRI photo is capable of responding in a number of ways. Almost all regions of our brain have different job functions, not just one. Said another way, specific brain structures rarely perform single tasks. This makes accurately interpreting the scan difficult (Logothetis, 2008; Shermer, 2008; Satel, 2013). This little-known fact stands in contrast to the specific explanation you often read at the bottom of many fMRI photos such as, “This is your brain craving cocaine.” While one can be reasonably sure that brains do crave cocaine, the caution is that whatever is lighting up has the capacity to perform other tasks, and that may cast some doubt on the original explanation. For example, sometimes the brightly colored area of a brain scan indicates that the brain is not lighting up for the reasons we thought, but it is in fact inhibiting other regions (Lilienfeld, Lynn, Ruscio, & Beyerstein, 2009).
Still another problem is that some in the neuroscience field reason backward. They infer a neural activation reflects a subjective experience like an anxious feeling or craving cocaine. They see some activity in the brain and conclude that this is where the anxious or craving feeling state occurs. There is a problem with that. We can put you in a state of fear and your amygdala will light up, but that does not mean that every time your amygdala lights up you are experiencing fear. In addition, the brain is extraordinarily complex. There is a constant volume of neural cross talk going on every second, plus the brain is constantly rewiring itself. That means the brain itself is changing. So a scan taken at one point is going to be a little different from one taken at another point. It gets complicated. We just can’t make gross inferences about psychological states unless the brain hot spot in question has been exclusively established as the cause of the process. That hasn’t happened yet, and a big reason why is that the fMRI devices do not generate high levels of precision (Shermer, 2008; Satel & Lilienfeld, 2015).
In addition, the fMRI scan is a time-delayed representation of increased blood flow. What you see in a brain scan is an after-the-fact representation. Recall that machines and computers have to do their interpretative work, which takes a little time. Then the scientists reading the scan need to translate what they are seeing. So, a perceived increased blood flow scan is just that—an interpretation of what the brain is really doing. Again, science is getting better at all this, but much work needs to be done to specifically link detailed brain hot spots to specific thoughts, emotions, sensations, and a host of other human states.
Organizations like the National Institute of Drug Abuse (NIDA) are somewhat confident that while its published scans demonstrate that “this is your brain craving cocaine,” they remain understandably cautious by using terms such as “linked to” or “associated with” cocaine or any drug effect to a certain brain region hot spot. In addition, if you read the NIDA material carefully they often include such phrases such as, “We don’t yet completely understand brain mechanisms.” This reflects a solid understanding of brain science research. The fMRI addiction findings are not quite to the point that they can conclusively state, “Drug X causes a precise brain area, Y, to light up.” Issues that hold them back from using the word “cause” is the interpretation problem previously noted and the lack of machinery sophistication at this time.
Not to overstate the brain complexity issue, but neuroscience has not found a specific area of the brain for gratitude or remorse. The feeling of empathy has been associated with at least ten different brain regions (Burton, 2014). The idea that addiction has a reward pathway in our brain from the ventral tegmental area to the nucleus accumbens to the prefrontal cortex is but a rudimentary theory at this time (NIDA, 2007). There is more complexity and accuracy to be established in this pathway, but discoveries are being made each year.
The brain is extraordinarily complex and science is only just beginning to understand its function. We remain far from determining precise brain hot spots of thoughts, emotions, and sensations, even addiction processing. The fMRI scans are intriguing, but at this time science does not quite comprehend it all. The point is that we just need to be a little cautious as to what we are really seeing when looking at those colorful brain scans.
Burton, R. A. (2014). A skeptic’s guide to the mind: What neuroscience can and cannot tell us about ourselves. New York, NY: St. Martin’s Press.
Kaku, M. (2015). The future of the mind: The scientific quest to understand, enhance, and empower the mind. New York, NY: Anchor Books.
Lilienfeld, S. O., Lynn, S. J., Ruscio, J., & Beyerstein, B. L. (2009). Great myths of popular psychology: Shattering widespread misconceptions about human behavior. West Sussex, United Kingdom: Wiley-Blackwell.
Logothetis, N. K. (2008). What we can and what we cannot do with fMRI. Nature, 453(7197), 869–78.
National Institute on Drug Abuse (NIDA). (2007). Understanding drug abuse and addiction: What science says. The reward pathway. Retrieved from http://www.drugabuse.gov/publications/teaching-packets/understanding-drug-abuse-addiction/section-i/4-reward-pathway
Satel, S. (2013). Don’t read too much into brain scans. Time. Retrieved from http://ideas.time.com/2013/05/30/dont-read-too-much-into-brain-scans/
Satel, S., & Lilienfeld, S. O. (2015). Brainwashed: The seductive appeal of mindless neuroscience. New York, NY: Basic Books.
Shermer, M. (2008). The brain is not modular: What fMRI really tells us. Scientific American. Retrieved from http://www.scientificamerican.com/article/a-new-phrenology/?page=2
Watson, S. (2008). How fMRI works. Retrieved from http://science.howstuffworks.com/fmri.htm