The subject is shown visual stimulants asking him to answer a simple question: Which would you prefer, a smaller amount of money sooner or a larger amount later?

 

As he makes his decision, University of Arkansas for Medical Science (UAMS) researchers use a 3 Tesla MRI to study what parts of the brain are being fed oxygenated hemoglobin. Those are the regions that are most active in the decision-making process. And they may hold the key to learning why some people are more likely to become addicted to gambling, alcohol, or other unhealthy habits – and how to treat those addictions.

Until recently, the researchers have had access to a 3 Tesla MRI only when the radiology department wasn't using it – late nights and weekends, in other words, which wasn't very conducive to recruiting research volunteers.

 

Now, UAMS has two 3 Tesla machines – the only two in the state – thanks to the purchase of a new $2.2 million, 10,000-pound Philips MRI that is capable of producing a magnetic field 60,000 times stronger than the Earth's. The new machine is housed at the Helen L. Porter and James T. Dyke Brain Imaging Research Center at UAMS, and it will be used by clinicians in the mornings and by researchers in the afternoons once it is fine-tuned and technical issues are resolved. The other model, a Siemens version, has been in use for a few years.

 

According to Marvin Stricklin, MHA, administrative/technical director for radiology, a 3 MRI allows a more detailed image of the brain and other body parts with a much smaller signal-to-noise ratio, and it will be able to detect smaller abnormalities than less powerful 1.5 MRIs.

 

"It just gives us greater detail of the brain itself, of the structural and functional anatomy, so we're seeing things with a 3 MRI that you cannot see with a lesser strength magnet," he said.

 

Stricklin said the machines have a larger aperture than older MRIs so that patients aren't touching the magnet, and a shorter bore that is about the size of a typical CT scanner. The 3 Teslas are also faster and quieter than older models. These factors should help claustrophobic patients withstand the discomfort of an MRI examination without having to resort to less reliable open MRIs.

 

Jeff Pitcock, MPH, neuroimaging data analyst for UAMS' Center for Addiction Research, is using the machine to study neural correlates of the decision-making process. In addition to the aforementioned functional magnetic research imaging study of hemoglobin patterns, researchers can do tractography, or diffusion tensor imaging, which can study the fiber tracts that connect brain regions. They can do magnetic resonance spectroscopy, in which they measure the metabolic makeup of specific brain regions. Voxel-based morphometry allows them to measure the volume and densities of the different brain regions.

 

Separate or combined, these techniques allow researchers to study the brain in ways that wouldn't be possible without the machine. Pitcock and other researchers, including Warren Bickel, PhD, director of the Center for Addiction Research, are publishing a study in the Journal of Neuroscience in which they found no differences in what brain regions were most active when subjects with no addictions other than cigarettes and no psychiatric disorders were presented with real money gains, hypothetical money gains, and hypothetical money losses.

 

Collecting the data for that study, which involved 30 participants, took a year because of the limited access to the Siemens machine. "If we were lucky, we might be able to scan two to three people on any given weekend," Pitcock said.

 

Studies such as these will allow researchers to better understand a decision-making process known as delayed discounting, a behavioral measure of impulsivity. People with addictive personalities place less importance on the future than their control populations, so perhaps researchers can find a neural correlate associated with the trait – and if so, a behavioral or pharmacological treatment.

 

"If we can ascertain if there is either a limbic-associated area or an executive functioning area that is more responsible for this discounting, then that can be utilized for intervention purposes," Pitcock said.