Researchers say they've discovered which regions of the brain are involved in the ability to resist, at least temporarily, the pleasures of a slice of cake or throwing another $50 on the poker table. Communication between the hippocampus (a region associated with memory and emotion) and the nucleus accumbens (a region associated with the brain’s reward system and involved in the process of addiction) is integral to the process of delayed gratification, according to a new study of rats in the European Journal of Neuroscience

McGill University psychologists trained rats to choose between two different shapes displayed on an iPad screen, receiving sugar pellets as a reward. They could choose one shape to receive a single pellet immediately, or another to receive four pellets a little bit later. After training, the rats were willing to give up the instant gratification of one sugar pellet in return for more pellets later.

However, when the researchers disrupted the circuit connecting the hippocampus and nucleus accumbens, the rats became unwilling to hold off for a larger reward, even if it only meant waiting a few extra seconds. Without it, the rats just couldn't wait. By contrast, disrupting functions in other parts of the brain, like regions involved in decision-making, did not affect the rats’ willingness to delay their dose of sugar. They still chose to delay gratification and wait for more pellets later. 

“In some ways this relationship makes sense; the hippocampus is thought to have a role in future planning, and the nucleus accumbens is a 'reward' center and a major recipient of dopamine, a chemical responsible for transmitting signals related to pleasure and reward,” lead author Yogita Chudasama said in a press statement. Further research with humans will be necessary, but these findings could eventually underpin the development of treatments for things like anxiety disorders, gambling addictions, and more.