Scientists at the Georgia State University, Georgia Regents University and Charlie Norwood VA Medical Center found that the brain uses sweet foods to form the memory of a meal. The paper shows how the neurons in the dorsal hippocampus — a part of the brain that is critical for episodic memory — are activated by consuming sweets. Episodic memory records autobiographical events and their particular time and context.
The team fed rats with a sweetened solution, made with wither sucrose or saccharin. They found that eating this meal showed significantly increased expression of the synaptic plasticity marker called activity-regulated cytoskeleton-associated protein (Arc) in dorsal hippocampal neurons compared to other types of food.
“We think that episodic memory can be used to control eating behavior,” said Marise Parent, professor in the Neuroscience Institute at Georgia State. “We make decisions like ‘I probably won’t eat now. I had a big breakfast.’ We make decisions based on our memory of what and when we ate.”
It probably won’t come as a surprise to anyone that increased snacking (both in quantity and frequency) has been associated with obesity. Research also shows that over the past three decades, children and adults are eating more snacks per day and deriving more of their daily calories from snacks, mostly in the form of desserts and sweetened beverages.
Previous work of the team showed how temporarily inactivating dorsal hippocampal neurons following a sucrose meal, during the period during which the memory of a meal forms, determines the rats to eat again sooner and ingest larger quantities of food.
A former London-based study investigated how disrupting the encoding of the memory of a meal in humans, such as by watching television, increases the amount of food they consume during the next meal. It also found that people with amnesia will eat again if presented with food, even if they’ve already had a meal.
The results of all these experiments illustrate the key role the brain has on meal onset and frequency, and how memory comes into play. To understand energy regulation and the causes of obesity, we need to have a better understanding of the organ’s internal workings, Parent said.
Now the team aims to determine if nutritionally balanced liquid or solid diets that typically contain protein, fat and carbohydrates have a similar effect on Arc expression in dorsal hippocampal neurons and whether increases in Arc expression are necessary for the memory of sweet foods.