| New Food-Addiction Link Found (Part Two) | |
For food stimulation, the volunteers were presented with foods they had previously reported as their favorites. The food was warmed to enhance the smell and the subjects were allowed to view and smell it, as well as taste a small portion placed on their tongues with a cotton swab. As a control, subjects were asked to describe in as much detail as possible their family genealogy during scans when food stimulation was not used. Study participants were also instructed to describe on a scale of 1 to 10 whether they felt hungry or desired food prior to food stimulation and then at five-minute intervals.
The researchers found that food stimulation in combination with oral methylphenidate produced a significant increase in extracellular dopamine in the dorsal striatum. There was also a correlation between the increase in dopamine triggered by food stimulation and methylphenidate and the changes in self-reports of hunger and desire for food. "This suggests the dopamine increases during the food/methylphenidate condition reflect the responses to food stimulation and not the isolated effects of methylphenidate," Dr. Volkow said.
This study shows for the first time that the dopamine system in the dorsal striatum plays a role in food motivation in the human brain. This relationship was not observed in the ventral striatum, which includes the nucleus accumbens, the area of the brain thought to be responsible for food reward. "We and others previously thought the nucleus accumbens was the primary brain region associated with regulating food intake by modulating reward and pleasure while eating," said study coauthor Gene-Jack Wang. "These findings challenge that belief."
This study was funded by the U.S. Department of Energy and the National Institute on Drug Abuse.
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