An important aim of neuroscience is to understand how decisions are made in the central nervous system that enable an animal to express one behavior instead of another. Clearly, decision-making processes require that multiple motor programs are coordinated with each other. The PI and Co-PI contend that such important issues can be understood by studying the model nervous system of the leech (Hirudo medicinalis). The simpler nervous system of the leech offers a premier system in which to study the underlying mechanisms of behavior. The presence of large and physiologically accessible neurons, coupled with a hierarchical organization, will facilitate cellular studies of locomotion and movement. In addition, their studies will focus on the behavioral roles of the neuromodulatory compound dopamine (DA), an important regulator of behavior in all animals. The researchers aim to determine how DA influences decisions about which behaviors to express. The central hypothesis of the research is that the network of DA secreting neurons in the leech nervous system functions in the choice and orchestration of behaviors that are part of the appetitive phase of feeding. Two primary aims are proposed: 1) To test whether DA alters biting and searching movements, 2) To determine how behaviors switch when command-like neurons in the brain are electrically stimulated in the presence or absence of DA. As part of this study, the activity of living brain neurons will be measured in behaving animals using a state-of-the-art optical imaging system of dyes whose color and intensity changes with the voltage of excited neurons. Such experiments will reveal how DA can influence populations of neurons so that they can select and shape the suite of locomotory behaviors that an animal can express. Because DA plays such a major role in regulating mammalian behaviors (e.g., locomotion, motivation and reward), our studies of DA, locomotion and feeding-related behaviors will likely have broad scientific significance. Many of the proposed experiments have been designed to be performed by college students to involve them in the process of science early in their careers.
