This is your brain, addicted

Scans explore role of automated responses for smokers, alcoholics, drug abusers

March 16, 2007|By Dennis O'Brien | Dennis O'Brien,Sun reporter

You might think reaching for that cup of coffee or cigarette is a simple decision.

But scientists believe the way we act to satisfy cravings involves a little-understood automated response - one we have no control over - and researchers in Baltimore are using brain scans to unlock its secrets.

"If there's an automated component to craving, we really want to understand how it works," says Elliot Stein, director of the neuroimaging lab at the Bayview campus of the National Institute on Drug Abuse in East Baltimore.

In a basement lab, Stein and other NIDA researchers routinely scan the brains of smokers, drug addicts and alcoholics with a functional Magnetic Resonance Imaging machine, or fMRI, to try to determine why their subjects have such a hard time kicking their habits.

The scientists are part of a growing research movement that's using fMRI to unlock the brain's secrets. The technology was developed in the early 1990s by scientists who discovered they could track increased blood flow to different brain regions in real time.

"We were trying to see changes in the brain as they were occurring, and not just look at brain structures," says Kenneth Kwong, a physicist at Harvard University and Massachusetts General Hospital who was instrumental in developing fMRI as a research tool.

Work at the NIDA lab is infused by the philosophy - backed up by years of research - that addiction is a brain disease, Stein says. He's convinced that a key to helping those trying to overcome addiction lies in understanding the brain's response to conscious and subconscious cues.

"There's a multiplicity of factors that are behind human behaviors. Why wouldn't there be a multiplicity of factors behind addiction and something like drug abuse?" Stein asked.

"Clearly, `just saying no' doesn't work."

Stein and NIDA colleague Britta Hahn are studying how cues trigger cravings in addicts. They want to know what happens in the brains of smokers when they see cigarettes, and in drug addicts when they see the kinds of drug paraphernalia that remind them of their habits.

Previous studies have established that images of cigarettes and drugs cue brain activity associated with cravings among smokers and drug addicts. But there are also unconscious cues that trigger less understood automated responses, they say.

Stein and Hahn's work is aimed at pinning down brain areas involved in both the conscious and unconscious cues. Known as cue reactivity, it's an emerging question in drug addiction research. Some of the findings apply to smokers, alcoholics and caffeine addicts, they say.

"You have to keep in mind that sometimes responses to these cues happen fast, and you might not even be aware of them," Stein said.

Stein and his colleagues are part of a research movement that's using fMRI to decipher what's actually going on in the brain.

Over the years, researchers have tapped fMRI to identify activity associated with a variety of mental and emotional processes, from pleasure and pain to deception and decision-making. Doctors also use fMRI, along with magnetic resonance spectroscopy, to track the progress of brain cancer treatments, said Dr. Rao Gullapalli, director of the MRI Research Center at the University of Maryland School of Medicine.

"It's pretty amazing, to be able to look inside the workings of someone's brain," said George Loewenstein, a researcher at Carnegie Mellon University in Pittsburgh. For example, Loewenstein has found that decisions about spending money can activate brain regions associated with pain.

In fMRI research, a volunteer lying on a table inside a cylindrical tube is given a test or task to perform while his brain is scanned.

The process of carrying oxygen-rich blood to specific brain regions alters the magnetic field that surrounds the volunteer. Radio waves help pin down the exact locations of where the brain activity occurs.

Experts can also probe the brain with positron emission tomography, or PET scans, but they require injecting volunteers with a radioactive dye for each test.

At the University of Maryland Dental School, Joel Greenspan, a professor of biomedical sciences, uses fMRI to study pain responses among people with chronically painful conditions, such as temporomandibular disorder.

In a study of 25 women published in 2004, Greenspan found that those suffering chronic pain were more sensitive to pain in other areas of the body than a control population. One long-term goal of research is the possibility of pain relievers that can block a receptor in the brain, known as the NMDA receptor, that becomes more active when someone experiences prolonged pain, he said.

For such work, Greenspan applies a flat-tipped probe to the backs of volunteers' fingers while they undergo fMRIs. The probe feels like a pin prick, but doesn't break the skin.

"It's not quite as sadistic as it sounds," Greenspan said.

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