One of the defining characteristics of mental disease is the loss of behavioral control and the rise of impulsiveness, poor decision making and a disconnect between what individuals do and what they want to do. There is a perceptive and straightforward measure or 'effect'that can be used to examine fundamental psychological processes involved in behavioral regulation of making choices and developing preferences. The relative reward effect (RRE) is observed as a neural or behavioral influence from past or future outcomes on the present outcome. It is a way of exploring primary outcome comparisons that is highly conserved across diverse organisms. It has been studied by numerous behavioral scientists, and the growing neuroscience literature supports involvement of the striatum and amygdala. Our own previous studies found significant RREs on neural activity in the striatum;however, we left the question open as to how these effects vary within this diverse brain structure. The dorsal and ventral striatum receive dramatically different inputs and are thought to be involved in distinct functions. Additionally, we intend to examine how the RRE varies between the striatum and amygdala- two interconnected brain regions involved in forming links between emotional states and motor output. We will use the most advanced neurophysiological methods to record single units in behaving animals during performance in relatively simple, single reward environments and more complex mixed reward environments. Comparisons on neural and behavioral data between these simple and more complex situations will be completed. Moreover, we include a study with inactivation of amygdala preceding recording striatal neural responses. This method is an innovative and sensitive way to explore the reliance between these two brain areas in processing relative properties of events. Our long-term goal is to decipher how the striatum and its diverse inputs distribute and compute reward information to produce appropriate behavior. The findings will open the way to understand how information flow breaks down in mental illness causing emotional and behavioral problems. The striatum and amygdala have both been found to be dysregulated in mental illness. Despite these major advances in understanding, there is limited knowledge for how outcome information is processed differently during pathological states and overall, what functional consequence to attribute to alterations in brain activity related to behavior. Data acquired will provide new ways to think about these issues and expand the study of neural processing related to mental health which is an essential part of the National Institute of Mental Health mission. The projects provide a rich and engaging environment for training students in methods that will be part of behavioral neuroscience in the long-term. New jobs will be created and careers fostered for young people eager to work on the biology of mental illness.
The project contains extensive relevance to mental health in that it is an investigation of how the brain makes comparisons over time and how these comparisons lead to better choices. This is an ubiquitous process and when done adaptively, it leads to positive affect, appropriate choices and healthy mental states. Delineating the details for how brain areas like the striatum and amygdala are involved in these fundamental processes opens the door to studying how the same abilities become disabled in mental illness and how new therapies can reinstate adaptive brain function and behavior.
