Using functional magnetic resonance imaging (fMRI) at Massachusetts General Hospital, Dr. Hans C. Breiter, principal investigator for the study, and his colleagues were able to measure activity in very specific regions of the brain during cocaine administration. Subjects were instructed to rate feelings of levels of the cocaine-induced "rush" and cocaine-induced craving. The fMRI produced a highly detailed map of brain activity while individuals were having these different experiences, and showed distinct patterns of activity in different parts of the brain associated with each experience.
Dr. Alan I. Leshner, Director of the National Institute on Drug Abuse (NIDA), National Institutes of Health, the Federal agency that funded the study, said, "These studies lay out in exquisite detail many of the different circuits of the brain that are activated during different behavioral experiences associated with using cocaine, and they suggest specific brain areas that might be targeted in developing new medications to either block individual aspects of cocaine's effects, like the rush versus the craving experiences, or as broader treatments for cocaine abuse and addiction."
Through previous studies with other techniques, scientists have gained numerous invaluable insights into how and where cocaine acts in the brain by recording nerve cell activity in the brains of laboratory animals treated with drugs. However, the animals cannot indicate what they are feeling during different states of drug-induced brain activity. Earlier techniques used in studying the effects of drugs of abuse on the human brain have been consistent with what was learned with animals, but have been unable to provide the same level of detail and specificity found in this fMRI study. "This is the first time that we have been able to show with this level of detail that the circuitry implicated in animals is actually the same as that involved in the brains of humans," Dr. Leshner added.
"An advantage of our approach [using noninvasive fMRI imaging of human subjects] is that we can actually match changes in brain activity in fine detail to the subjective sensations described by the drug user," said Dr. Breiter.
The researchers found that the cocaine rush was associated with early and short-lived increases in activity in a number of brain regions. Those regions included some areas of the cortex, the outermost area of the brain responsible for conscious thought, and some structures of the limbic system, a deeper area involved with emotions. On the other hand, cocaine craving was associated with prolonged activation of the nucleus accumbens, a region known to be involved in producing the pleasurable effects of drugs. Craving was associated also with sustained decreases in activity in some brain areas, such as the amygdala, which plays a role in aggression and other emotions.
The study on brain activity in drug-induced emotions will be published in the September 25 issue of Neuron. For more information about the study, call the NIDA Press Office at (301) 443-6245.
NIDA supports more than 85 percent of the world's research on the health aspects of drug abuse and addiction. The Institute also carries out a large variety of programs to ensure the rapid dissemination of research information and its implementation in policy and practice. Further information on NIDA research and other activities can be found on the NIDA Home Page at http://www.nida.nih.gov.