Philadelphia, Penn. ¬– Most people know which foods make them feel good and give them pleasure. But now scientists have a way to see it in their eyes.
At Drexel University scientists tested 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.
In the eye’s retina, dopamine is released when the optical nerve activates in response to light exposure.
Jennifer Nasser, an associate professor in the department of Nutrition Sciences in the College of Nursing and Health Professions at the university, led the study.
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.
Chocolate versus water
The participants’ responses were significantly greater in the presence of food and drug stimuli versus the response to light when participants ingested a control substance like water.
“What makes this so exciting,” says Nasser, “is that the eye’s dopamine system was considered separate from the rest of the brain’s dopamine system. So most people– and indeed many retinography experts – would say that tasting a food that stimulates the brain’s dopamine system wouldn’t have an effect on the eye’s dopamine system.”
Nasser’s study was a small-scale study. If the technique is validated through additional and larger studies, Nasser says she and other researchers can use ERG for studies of food addiction and food science.
“My research takes a pharmacology approach to the brain’s response to food,” says Nasser.
“Food is both a nutrient delivery system and a pleasure delivery system, and a ‘side effect’ is excess calories. I want to maximize the pleasure and nutritional value of food but minimize the side effects. We need more user-friendly tools to do that.”