How do we know if it was worth the wait in line to get a meal at the new restaurant in town? To do this our brain must be able to signal how good the meal tastes and associate this feeling with the restaurant. This is done by a small group of cells deep in the brain that release the chemical dopamine. The amount of dopamine released by these cells can influence our decisions by telling us how good a reward will be in the future. For example, more dopamine is released to the smell of a cake baking relative to the smell of leftovers. But does waiting change how dopamine is released?
A new study in Cell Reports by Matthew Wanat, assistant professor of biology at The University of Texas at San Antonio (UTSA), sheds light on how dopamine cells in the brain signal the passage of time. Wanat’s study used a technique called voltammetry to record dopamine release in rodents trained using Pavlovian conditioning. This task used two different tones that both predicted the delivery of a food reward. One tone was presented only after a short wait while the other tone was presented only after a long wait. Wanat and colleagues found that more dopamine was released to the short wait tone. These results highlight that when dopamine neurons respond to cues, faster is better.