Research projects

Revealing functional design of insect “microbrain”

　　 The major goal of our laboratory is to reveal the functional design of insect brain, which we have termed “microbrain (1, 2)”. To achieve this goal, we are studying molecular, cellular and neuron-network mechanisms of visual and olfactory learning in insects. One of our research focuses is the role of the mushroom body, an association center of the insect brain, in various forms of learning.

Analysis of changes in activity of brain neurons induced by learning

　 We have shown that cockroaches exhibit conditioning of salivation, as do dogs (3-5), and that the mushroom body plays an essential role in this learning (in preparation). We are examining changes in activities of brain neurons associated with salivary conditioning.

Analysis of “cognitive” processes underlying insect classical conditioning

　　 We have studied the roles of the octopaminergic reward system and dopaminergic punishment system in olfactory and visual pattern and color learning in crickets (6-8) and have concluded that sophisticated information processing, often called “cognitive” process, underlies learning in insects (9). We are examining neural mechanisms of such sophisticated information processing in order to obtain a better understanding of functional organization of the insect brain.

Elucidation of higher-order learning phenomena in insects

　 We have developed paradigms to study contest-dependent olfactory learning in crickets (10) and cockroaches (11). This paradigm will help to elucidate neural basis of sophisticated information processing in the insect brain.

Analysis of odor representation in the primary olfactory center in insects

　　 We are studying how olfactory information is represented in the first olfactory center, the antennal lobe, in the cockroach brain. Our ultimate goal is to develop an “artificial nose system”, based on neural algorithms for odor discrimination by insects. 　 In addition, we are examining functional organization of the antennal lobe of insects, in collaboration with Dr Hiroshi Nishino, Research Institute for Electronic Science, Hokkaido University.

Revealing signaling cascades underlying the formation of long-term memory

　　 We have shown that the NO-cGMP signaling system plays an essential role in the formation of visual and olfactory long-term memory (LTM) in insects, in using pharmacological studies (12). The current purpose of our study is to reveal complete signaling cascades underlying LTM formation. We are using RNA interference techniques to extend this study (13). Moreover, we are also developing transgenic technology for the study of molecular mechanisms of LTM formation in crickets.

Elucidating brain mechanisms of pheromone communication by social insects

　　 Social insects such as ants are equipped with sophisticated communication system by means of pheromones. We are studying how alarm pheromone information is processed in the ant brain (14-17).

References

  1. Mizunami M., Yokohari F., Takahata M. (1999) Exploration into the adaptive design of the arthropod “Microbrain”. Zool. Sci. 16: 703-709.
  2. Mizunami M., Yokohari F. and Takahata M. (2004) Further exploration into the adaptive design of the arthropod “microbrain”: I. Sensory and memory-processing systems. Zool. Sci. 21:1141-1151.
  3. Watanabe H. and Mizunami M. (2006) Classical conditioning of activities of salivary neurons in an insect. J. Exp. Biol. 209:766-779.
  4. Watanabe H. and Mizunami M. (2007) Pavlov’s cockroach: classical conditioning of salivation in an insect. PLoS ONE, 6:e529.
  5. Watanabe H., Sato C., Kuramochi T., Nishino H., and Mizunami M. (2008) Salivary conditioning with antennal gustatory unconditioned stimulus in an insect. Neurobiol. Learn. Mem. 90: 245-254.
  6. Unoki S., Matsumoto Y. and Mizunami M. (2005) Participation of octopaminergic reward system and dopaminergic punishment system in insect olfactory learning revealed by pharmacological study. Eur. J. Neurosci. 22: 1409-1416.
  7. Unoki S., Matsumoto Y. and Mizunami M. (2006) Roles of octopaminergic and dopaminergic neurons in mediating reward and punishment signals in insect visual learning. Eur. J. Neurosci. 24: 2031-2038.
  8. Nakatani Y., Matsumoto Y., Mori Y., Hirashima D., Nishino H., Arikawa K. and Mizunami M. (2009) Why the carrot is more effective than the stick: Different dynamics of punishment memory and reward memory and its possible biological basis. Neurobiol. Learn. Mem. (in press)
  9. Mizunami M., Unoki S., Mori Y., Hirashima D., Hatano A., and Matsumoto Y. (2009) Roles of octopaminergic and dopaminergic neurons in appetitive and aversive memory recall in an insect. BMC Biology (in press)
  10. Matsumoto Y. and Mizunami M. (2004) Context-dependent olfactory learning in an insect. Learn. Mem. 11: 288-293.
  11. Sato C. Matsumoto Y. Sakura M. and Mizunami M. (2006) Contextual olfactory learning in cockroaches. NeuroReport. 17:553-557.
  12. Matsumoto Y., Unoki S., Aonuma H., Mizunami M. (2006) Nitric oxide-cGMP cascade is critical for cAMP-dependent long-term memory formation. Learn. Mem. 13:35-44.
  13. Takahashi T., Hamada A., Miyawaki K., Matsumoto Y., Mito T., Noji S., and Mizunami M. (2009) Systemic RNA interference for the study of learning and memory in an insect. J. Neurosci. Methods 179:9-15.
  14. Yamagata N., Fujiwara-Tsujii N., Yamaoka R. and Mizunami M. (2005) Pheromone communication and the mushroom body of the ant Camponotus obscuripes (Hymenoptera: Formicidae). Naturwiss. 92:532-536.
  15. Fujiwara-Tsujii N. Yamagata N. Takeda T. Mizunami M. and Yamaoka R. (2006) Behavioral responses to the alarm pheromone of the ant Camponotus obscuripes (Hymenoptera: Formicidae). Zool. Sci. 23: 353-358.
  16. Yamagata N., Nishino H. and Mizunami M. (2006) Pheromone-sensitive glomeruli in the primary olfactory center of ants. Proc. R. Soc. B. 273: 2219-2225.
  17. Yamagata N., Nishino H. and Mizunami M. (2007) Neural pathways for the processing of alarm pheromone in the ant brain. J. Comp. Neurol. 505: 424-442.

Message

　　　 The goal of our study to open a new field of evolutionary neurobiology. Students and young researchers interested in the brain, behavior and evolution are most welcome to our laboratory.

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