Collaborative Research: The neurobiology of dopamine in the leech and the modulation of locomotor behaviors

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

Dopamine (DA) is an important and universal modulator of motor control, but neuroscientists have yet to determine precisely how DA-containing neurons and their targeted circuitry choreograph specific locomotor programs. This has been an especially daunting task in studying the control and initiation of locomotion in higher vertebrate systems. Related to this issue of locomotor regulation is the idea of decision-making, and how one form of locomotion is selected instead of another, for example, the choice between crawling vs. swimming. This collaborative research project is addressing such important questions at the level of single identified neurons; often at times while the intact animal is behaving. The simpler nervous system of the leech, Hirudo medicinalis, was selected for study because it contains relatively large and physiologically accessible neurons and a hierarchical circuit organization, thus facilitating studies of locomotion, body movement and descending control. Specifically, the collaborative research team is characterizing constituents of the pattern-generating network underlying crawling-related behavior, and determining how DA changes the properties of neurons to facilitate their participation in crawling. This approach will lead naturally to an understanding of the neuronal bases of decision-making, because it has been found that whenever DA triggers crawling then swimming is inhibited. The collaborative research team will use a variety of behavioral, electrophysiological, and anatomical methods to study how DA promotes crawling behavior. They will also image neuronal circuits influenced by DA using a state-of-the-art voltage sensitive dye imaging system. Many of the experiments being conducted involve graduate and undergraduate students. Other experiments, with minor modification, incorporate the participation of younger K-12 students. The collaboration with Dr. Crisp at St. Olaf College, an undergraduate-only research institution, provides an additional and valuable exchange of undergraduate training and mentoring opportunities. The projects and technological components of the proposal are inherently integrative, spanning disciplines from Animal Behavior to Cell Biology/Neurobiology, Computational Neuroscience, Physics, and Engineering.