The first step in understanding how the brain produces motivational or addictive behavior is to understand the exact infrastructure of the reward system. Which neurons are connected to which? How do specific regions in the reward system affect the activity of other regions in the system? One of our goals is to dissect cell-type-specific circuits in the reward system and examine the physiology of specific cells in those circuits. We are specifically interested in the ventral pallidum and the nucleus accumbens and how specific neurons in those regions interact with each other and with other regions of the reward system. To achieve this we utilize advanced neural tracing tools combined with in vivo and ex vivo optogenetics, chemogenetics and electrophysiology in various lines of transgenic mice.