Imaging Studies Illuminate Brain's Response ...( he brain to cocaine the reseachers use...)

he brain to cocaine, the reseachers used functional magnetic resonance imaging (fMRI), a technique largely developed at the MGH. Using fMRI, areas of increased brain activity, characterized by increased levels of oxygen in the blood, can be superimposed on detailed images of brain structures. Functional MRI scans were made of 10 volunteer participants - all of whom were carefully selected cocaine addicts - as they received cocaine injections and for 13 minutes following the injection. At 15-second intervals throughout the testing period - starting 5 minutes before the injection - participants reported the extent to which they experienced feelings of rush, high, low or craving.

Results indicated that more than 90 areas of the brain showed increased activity in response to cocaine. Many areas associated with thought and emotion showed an immediate although brief response of increased activity, which was associated with reported feelings of "rush" and euphoria. Other areas showing an immediate response remained activated longer, extending into periods when participants reported feelings of craving. One of the most significant among these is the nucleus accumbens, believed to be associated with reward reinforcement. In addition, the area called the amygdala, also associated with the reward system, showed lower-than-normal activity, particularly during periods of reported craving.

The results suggest, the researchers believe, that while there are distinct areas involved in the various experiences of cocaine use, it is not simply a matter of turning certain structures on to produce a particular response. Instead the patterns of which areas are activated in what sequence and for how long seem to determine the feelings generated, particularly in the case of craving.

"Our observations regarding the nucleus accumbens were probably the most unexpected," says Breiter. "That area has been thought to be involved in reinforcement, so we expected it would
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Contact: Sue McGreevey
mcgreeveys@a1.mgh.harvard.edu
(617) 724-2764
Massachusetts General Hospital
26-Sep-1997

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