Grant: Project Grant

We are continually faced with choices and must consider the benefits associated with making one particular choice over another. However, we do not always choose the most beneficial option if the payout is very hard to obtain or if we are unsure about its availability. Another cost to consider is the time required to benefit from our actions. Often is it advantageous to forego something that immediately satisfying and wait for something better. For example, despite the short-term pleasure of consuming junk food, we may instead opt for healthy food knowing that the long-term benefits will be greater. Many disorders, such as schizophrenia, depression, drug addiction and Alzheimer's disease are associated with impulsive preference for immediate rewards. We are interested in the possibility that newborn neurons that are added to the adult brain could reduce impulsivity and promote preference for delayed, advantageous rewards. New neurons are continually added to the brain of all animals, including humans. They are largely added to the hippocampus, and they contribute to hippocampal functions in memory but their exact role remains unclear. Current evidence indicates that the hippocampus is important for mentally recreating past experiences and for creating mental representations of possible future experiences. The hippocampus may reduce impulsivity by enabling individuals to envision possible future experiences and choose the behaviors that lead to long-term beneficial outcomes. However, a role for new neurons in impulsivity has never been investigated. To test this role for new neurons we will block neurogenesis in rats and assess their ability to choose a large delayed reward over a small immediate reward. We will also examine how learning to choose delayed rewards activates circuits of new neurons, to see if their functions are different from older neurons. These findings will be important for developing new treatments for disorders of impulsive decision-making.