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Understanding Brain Imaging

Daniel Lende and Greg Downey run the though-provoking Neuroanthropology blog. Daniel also teaches a class at University of Notre Dame, and he asked his students to submit group-based blog posts in lieu of the traditional final essays. He explains more on Why A Final Essay When We Can Do This?.

Below you have a spectacular post written by 4 of his students. They show how brain imaging is starting to provide a window into the plasticity (glossary here) of our brains, and how our very own actions impact them. For good and for bad.

Understanding Brain Imaging

— By Chris Dudley, Matt Gasperetti, Mikey Narvaez, and Sarah Walorski

Do you remember the anti-drug public service announcement from the 1980s that showed an egg frying in a hot pan which represented your brain on drugs?

During the 1990s, brain imaging moved beyond fried eggs as computer technology allowed researchers to process large amounts of data required for functional imaging approaches. As a result, the PSA mentioned above no longer provides the most accurate analogy illustrating what happens to the brain when exposed to drugs.

Today, brain imaging research has helped create a sophisticated “disease model of chemical dependence related to changes in the function of neurotransmitters and receptors in the brain. These circuits are responsible for reward processing, memory and learning, motivation and drive, in addition to control (Nora Volkow describes these circuits in a 2004 literature review).

This particular post focuses on the techniques used most commonly to study the brain’s role in addiction and other mental health problems. We will cover the principle behind each method, advantages and limitations of each, and provide an example of the results that can be obtained.

Beyond the Frying Pan: EEG and CT

Electroencephalography (EEG) and Computed tomography (CT) were two of the first methods used to study the brain. EEG utilizes electrodes placed on the scalp that measure electrical impulses, whereas CT creates a three-dimensional image of the brain with two-dimensional x-rays.

EEG is a non-invasive procedure with high temporal resolution; it is often used to record the brain’s response to a stimulus (e.g. an individual ingests a drug and the change in brain activity is recorded).

EEG is limited because it can only record data from the surface of the brain. In addition, EEG does not produce images of the brain it only measures electrical impulses.

CT is used to create three-dimensional images. Unfortunately, CT cannot produce high-resolution images of soft tissue (i.e. the brain) and requires high levels of radiation. While CT is still used, predominately to create images of the body, it has to be used infrequently to avoid excessive radiation exposure. Although EEG and CT did not teach us much about addiction, these methods were the technological precursors to more egg-cellent brain imaging methods.

Unscrambling the Mysteries of the Brain with MRI and fMRI

Ever wonder what it’s like to have radio waves sent through your brain? Well, Magnetic Resonance Imaging (MRI) may be for you! MRI produces high quality images of the brain by using a large, cylindrical magnet to create a magnetic field around the head. Radio waves are sent through this field and alter hydrogen nuclei in the brain. These detectable changes are subsequently transmitted to a computer and used to generate a series of images.

Using these images, scientists are able to determine minute changes in the brain that occur over time by comparing different MRI scans.

MRI is useful because it can produce higher resolution images than CT scans and does not expose patients to excessive radiation. On the contrary, MRI is limited because there is no way to produce high-resolution images measuring temporal change.

This leads to the recent development of Functional Magnetic Resonance Imaging (fMRI). This technique, developed only recently, has allowed scientist to use MRI technology to capture images of various brain functions.

Functional MRI focuses on the flow of oxygenated blood within the brain. To simplify things, when an area of the brain is stimulated, oxygenated blood rushes to that area. Functional MRI is able to capture this flow of blood because of the slight difference in magnetism between oxygenated and deoxygenated blood.

This method is advantageous because it allows researchers to capture a series of images every second. These images can be used to create “movies” monitoring changes in brain activity.

By producing sequential images, fMRI records the areas of the brain that are activated. In addition to detecting substance use, fMRI is also a good lie-detecting device, as it senses activity in certain regions of the brain associated with specific behaviors.

Like all good things, including eggs, which contain a great deal of cholesterol, there is a downside to fMRI: blood flow is only an indirect measure of neuronal activity and fMRI only shows where activity takes place not exactly what is going on.

PET: Great Acronym, Great Images

Positron Emission Tomography (PET) is another commonly used brain imaging technique. PET, which is derived from CT, was the first functional imaging technique.

This method utilizes small amounts of radiotracers (i.e. molecules with a short-lived radioactive constituent atom such as carbon-11 or oxygen-15), which are localized by sensors that create computer-compiled images. These images depict the relative amount of radiotracer present by using a color gradient red being the highest concentration and blue the lowest.

Like fMRI, PET can be used to study regional cerebral blood flow (rCBF) via radio-labeled water in the bloodstream. Additionally, PET can look at glucose metabolism that shows regional neuronal activation.

Unfortunately, PET cannot achieve the temporal or spatial resolution possible with fMRI, and uses trace amounts of radiation: only one PET scan is allowed per year due to concerns regarding radiation exposure.

PET is most useful when studying neurotransmitter function and holds an advantage in temporal and spatial resolution over SPECT (discussed below).

By using a radio-labeled neurotransmitter, it is possible to study the location a neurotransmitter’s action, the amount of neurotransmitter release, and abundance of receptor levels. This has relevance in addiction studies, which have shown that dopamine receptor levels decrease with long-term cocaine use, leading to tolerance to low drug doses.

The only downside is that it takes time to develop appropriate radiotracers. Currently, the dopamine, GABA, and cannabinoid circuits can be examined, but suitable radiotracers for other neurotransmitters are still lacking. It is likely that future research will solve this problem.

Egg SPECT to Be Amazed

The name Single Photon Emission Computerized Tomography (SPECT) sounds impressive because it is. This method utilizes tracers that are directly injected into the body’s blood flow to highlight the level of neuronal activity in the brain.

After tracers are injected, a “gamma” camera rotates around the head to record data, and a computer uses the data to construct 2D or 3D images of active brain regions inactive areas of the brain show up as dark voids.

SPECT confirms areas of the brain that correspond with a person’s neural activity, and can be used to identify symptoms associated with drug use or mental illness. It can track the effects of counseling and medications: as an individual gets better, brain areas will change in activity level.

Although SPECT can’t create images as detailed as a PET scan, images can be viewed in both 2D and 3D. This method is not very expensive, and the procedure doesn’t need as many technical and medical staff to complete. The following SPECT images illustrate the effect of drug use on brain function.

SPECT not only shows damage, but also shows improvement when substance use is discontinued.

To see more examples of how the brain is affected by drug and alcohol use using SPECT, click here:

Beyond Brain Imaging

We have come a long way since the frying pan days. Clearly, the results of brain imaging studies are very useful in that they help researchers better understand what happens to a brain that has been fried by drugs.

Additionally, potential drug therapy treatments have been suggested based on the “circuits” model. The general aim of this approach includes decreasing a drug’s reward value, dissociating drug use from pleasurable memories, and restoring normal brain activity.

While brain imaging is a very useful tool, it does not provide a complete understanding of addiction. Each technique has limitations, as described above, but future developments are sure to strengthen these technologies. In addition, treating addiction purely as a brain disease has its own limitations, in that it ignores the powerful socio-cultural factors that contribute to drug use.

And just like anything else within the scientific realm, it is crucial that all hypotheses be rigorously tested: quality of research methods, and restraint when interpreting results, must not be sacrificed in order to draw exciting conclusions.

Finally, it is important to note that brain imaging is only able to show correlations in data, not causations: as a wise professor once said, “lines drawn on a map cannot show you why countries wage war.”  However, in the future, increased scientific understanding of brain addiction, as well as the results of future imaging studies, may be able to show how borders change as a result of war.


Remember, this blog post was written as part of a Neuroanthropology class. You can find the other seven blog posts by clicking on Why A Final Essay When We Can Do This?. Enjoy!

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5 Responses

  1. Kerri says:

    I have suffered with a mood disorder (Major Depression) for over 10 years. I know SPECT imaging is used now in treatment situations, do you have any information regarding this research or how it can be used by the consumer? -Thanks, Kerri

  2. Jacob says:

    I met Dr. Amen at a lecture he gave and then participated in his brain study of injured and uninjured brains. I learned a lot about the damage that can occur even from normal children’s bangs to the head – the kind that happen to most kids who engage in sports.

    If you are interested in the brain and how it works, I highly recommend reading “”My Stroke of Insight”” by Dr. Jill Bolte Taylor. It’s on the NY Times Bestseller list and it’s a wonderful book. Dr. Taylor’s talk at TED dot com is also AMAZING! Oprah interviewed Dr. Taylor and you can check that out on And Time Magazine named Dr. T one of the 100 Most Influential people in the world. Having read her book, I can see why all the attention.

    Dr. Amen’s book is brain science and it’s great at that. Dr. Taylor is a Harvard Brain Scientist, but what she writes about is the science and much more. She really cracks the code to understand how our brains (right and left hemispheres) work and she explains how we can get into our right brain and be happier and more joyful. Aside from any of the science, My Stroke of Insight is also just a great story.

  3. Alvaro says:

    Dear Kerri, brain imaging such as SPECT may be useful for professionals, but is not the main tool for either diagnosis or treatment. So it can be misleading for consumers to expect too much from it. I encourage you to consult with your doctor: he or she is the most qualified person to help you.

    Jacob: many thanks for your note. I heve in fact already ordered My Stroke of Insight for summer reading!

  4. Nancy says:

    I met Dr. Amen too – in San Diego at a meeting by one of the Secret authors. He convinced me to try to get my son who plays soccer to wear the headgear.
    I also heard Dr. Jill Bolte Taylor’s TED Talk video- it was sent to me, and I read her book MY STROKE OF INSIGHT, which was one of the most powerfully moving and inspiring books I’ve read in ages. The PhD brain scientist’s inside view of her own stroke was fascinating. The spiritual lessons and right/left brain lessons were profound.
    THank you for sharing that Jacob!

  5. Jayman says:

    Very good article. Good disection of the different options available for patients seeking further diagnosis and insight.

    I actually use the PET and SPECT images shown here during lectures at my addictions clinic.

    I welcome suggestions on where to find new research on addiction and brain disease.

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