Ren Weidman and Dr. Travis Oliphant, Electrical and Computer Engineering

In recent years the fields of medicine and physiological research have made many advancements as a result of application of technology. One example of this is the device known as the Magnetic Resonance Imaging machine (MRI). MRI machines use innovative methods based on principles of physics and electronics to effectively attain a cross-sectional view of the human body. The MRI machine emits an electromagnetic field in the presence of a static field to manipulate the nuclear spin of hydrogen atoms in the body. The received signal can then be interpreted and reconstructed to plot a picture of the section examined. This is all done quickly and without the negative side effects of radioactive materials or surgery. A particular application of MRI machines is referred to as functional MRI (fMRI). Functional MRI specifically monitors brain activity by using the contrast difference resulting from increased oxygenated blood flow to active areas of the brain.

It has been remarked that exercise increases one’s awareness and ability to focus. “For years many exercise enthusiasts have suspected that exercise positively affects the brain as well as the body … Now several biological studies indicate that working out does benefit the brain.”¹ It has been shown that people “that improved their aerobic fitness (VO2 max) by walking experienced significant improvements in thought processes such as planning, scheduling, and working memory–all of which depend, in part, on the integrity of the prefrontal and frontal cortex.”² In fact, the society for neurosciences has stated that “much of the new research suggests that exercise positively affects the hippocampus, a sea-horse shaped brain structure that is vital for memory and learning”³ Can this increased mental ability be observed using fMRI? The purpose of this study is to test the effectiveness of the MRI machine in studying the immediate results of exercise on mental activity.

The hypothesis formulated prior to the experiment stated that the observed effect of exercise on brain functionality could be a result of one or a combination of three different causes. First, the increased mental ability could be a result of more oxygenated blood flowing through the brain. This increase in blood flow would cause a greater amount of oxygen to be introduced to those areas of the brain used for thinking. Also, greater awareness may come from a greater portion of the brain being active. Exercise would cause this because when exercising, an individual’s average blood flow increases through all areas of the body. This could be detected by the MRI scans by comparing color intensities in common areas before and after exercising, given that the contrast is great enough. Second, the observed effect may be a result of chemicals called endorphins that are released while exercising. If this is the case, fMRI analysis of the brain would not indicate any substantial differences. Third, the enhanced abilities resulting from exercise may be a result of some other factor not yet considered. Most likely, causes falling in this third area also would not be observed using fMRI.

The experiment was done by taking two base scans of a subject, having the subject run for 12 minutes and then taking another pair scan. During the three minutes of each scan, the subject did nothing for the first and last 30 seconds and was required to work on ACT math problems during the intervening time. This was done in an effort to excite the areas of the brain. Three subjects were used in this experiment. A greater number of participants would have increased accuracy, but it also would have increased price.

After the acquisition of the images, they were run through an analyzing program written by David Thayer. This program compared pixels of the same location in the brain at different moments in time (reading math problems vs. not reading math problems) to determine if that ‘pixel’ of area was active. Significant change in the color of the pixel indicated a difference in blood flow to that area. Through numerous comparisons, averages and advanced statistical analysis, the program attained a new image in which those areas of the brain that were active are indicated by color.

The processed images were informative, in part because they highlighted problem-causing factors that need to be overcome to gain accurate and reliable results. The main issue that needs adjustment is the issue of head movement while inside the MRI machine. The head must be kept as still as possible in order for the information to be properly processed. Slight movements can result in faulty interpretations, because the program perceives two different parts of the brain as being the same, and thus (because brain density is not uniform) it may indicate brain activity where there is none. The second factor is that different math problems require different skills to solve and thus activate different areas of the brain. To compensate for this, a different, simpler activity should be required of the subjects.

Though these problem-causing factors were significant enough to nullify the ability to state any definite conclusion, there were trends that were revealing. Of particular note, in many instances (though not every time) scans of the brain taken before exercise showed less activity than the scan of the same portion of the brain taken after exercise. This was observed in both in the global and local sense (see Figures 1 and 2 below). This would lead and observer to believe that perhaps the first hypothesis is correct.

Further study of this phenomenon using fMRI and other methods of investigation would be very interesting. Continued examination with fMRI is of particular appeal because now the prominent pitfalls are known and can be avoided.

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¹http://apu.sfn.org/content/Publications/BrainBriefings/exercise.html Society for Neuroscience Publications
²http://www.physsportsmed.com/issues/2000/11_00/ed_notes.htm The Physician and Sports Medicine Journal
³http://apu.sfn.org/content/Publications/BrainBriefings/exercise.html Society for Neuroscience Publications