第1103回生物科学セミナー

Circuit mechanisms underlying olfactory learning

Dr. Yun Zhang(Department of Organismic and Evolutionary Biology, Center for Brain Science, Harvard University)

2016年06月09日(木)    11:00-12:30  理学部3号館 303号室   

Olfaction is a fundamental sense that guides behavior in many animals. Experience profoundly shapes the representation of an odor to an animal. However, how learning modulates olfaction-guided behavior is not fully understood, partly due to our limited understanding of the underlying neural circuits. Using a form of olfactory learning in Caenorhabditis elegans that is analogous to the Garcia effect, we systematically pursue the circuit mechanisms of learning. We have functionally mapped a neuronal network, from sensory neurons to motor neurons, that encodes both the naive and learned olfactory behaviors, revealing organizational principles for neural circuits of learning. We have characterized physiological property of each tier of the circuits and correlated the neuronal attributes with behavior. Particularly, we have found that the key interneuron of the learning circuit encodes motor outputs with compartmentalized axonal activity and sensory inputs with synchronized activity. We now show that these two activity patterns interact to integrate sensory and motor information, directing odor-guided chemotactic movements. Learning modulates the sensorimotor integration to generate experience-dependent changes in behavioral response. Meanwhile, our studies have also revealed a critical role of neuromodulators in shaping the state of the learning circuit. We are currently addressing how neuromodulators coordinate the activity of the learning circuit with whole animal physiology to regulate learning in a context-dependent manner. Together, our findings provide mechanistic insights into the neural circuits of learning at all levels from sensory perception to motor execution.