PHILADELPHIA (June 24, 2013) The brain's pleasure response to tasting food can be measured through the eyes using a common, low-cost ophthalmological tool, according to a study just published in the journal Obesity. If validated, this method could be useful for research and clinical applications in food addiction and obesity prevention.
Dr. Jennifer Nasser, an associate professor in the department of Nutrition Sciences in Drexel University's College of Nursing and Health Professions, led the study testing the use of electroretinography (ERG) to indicate increases in the neurotransmitter dopamine in the retina.
Dopamine is associated with a variety of pleasure-related effects in the brain, including the expectation of reward. In the eye's retina, dopamine is released when the optical nerve activates in response to light exposure.
Nasser and her colleagues found that electrical signals in the retina spiked high in response to a flash of light when a food stimulus (a small piece of chocolate brownie) was placed in participants' mouths. The increase was as great as that seen when participants had received the stimulant drug methylphenidate to induce a strong dopamine response. These responses in the presence of food and drug stimuli were each significantly greater than the response to light when participants ingested a control substance, water.
"What makes this so exciting is that the eye's dopamine system was considered separate from the rest of the brain's dopamine system," Nasser said. "So most people and indeed many retinography experts told me this would say that tasting a food that stimulates the brain's dopamine system wouldn't have an effect on the eye's dopamine system."
This study was a small-scale demonstration of the concept, with only nine participants. Most participants were overweight but none had eating disorders. All fasted for four hours before testing with the food stimulus.
If this technique is validated through a
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