In Drosophila, most odorants elicit attractive or repulsive behaviors. Each Odorant typically activates several olfactory receptors and results in activities in glomeruli with a distinct spatial pattern in the antennal lobe. However, for odor information from individual olfactory sensory input, its behavioral consequence is still unclear. In order to comprehensively study the role of individual glomerulus in the olfactory information process, we use the transgenic Channelrhodopsin2 (ChR2), making specific neurons to be light sensitive, and a remote control system for neural activities with the blue light LED (470nm) to do behavioral essays. Our study demonstrated that the blue light- stimulated individual glomerulus elicited either attractive or repulsive behaviors. These results answered a fundamental question for the activation of individual glomeulus. Furthermore, when activated two glomeruli- DM6 and VA6, which mediates attractive behavior by odorants when activated alone, through activating them at the same time abolished the attractive behavior. After we block the neurotransmission of one type of local neurons (LNs) in antenna lobes, the preference of the fly changed from no preference to favor the combined odorants again. Together, these results indicated that the interactions between individual glomerulus in the antennal lobes might modulate output for innate behaviors.

在一般環境中，多數的味道都會引發果蠅做出迎趨或是逃避的反應。大部分的味道都會和一種以上的嗅覺受器結合，而這些嗅覺受器下游的嗅覺感受神經細胞也會因此而被激發。屬於同一種類嗅覺受器的嗅覺感受細胞，會集中到果蠅腦中的同一顆嗅小球當中。目前我們已知果蠅對味道的反應，是因為激發了多種嗅覺感受神經細胞，但是如果只激發單一種類嗅覺感受神經細胞會造成什麼行為結果則仍然未知。為了研究單一種類嗅覺感受器神經細胞在果蠅行為中扮演的角色，我們利用轉殖的第二型離子通道視紫質(ChR2)，以刺激送到特定嗅小球內的嗅覺感覺神經細胞，並用藍光LED來遙控神經動作。我們的研究發現，單獨刺激屬不同種類的嗅覺感覺神經細胞，就會造成果蠅有趨向或是迴避的行為，這項資料提供了我們最基本的嗅覺系統運作變數。我們更進一步想了解如果同時刺激屬於兩個不同神經球的嗅覺感覺神經細胞，果蠅會有什麼反應。我們利用某些只會刺激單一種類嗅覺感受神經細胞的氣味以及表現第二型離子通道視紫質在另一種嗅覺感受神經細胞，結果發現如果同時激發集中於DM6以及VA6兩顆嗅小球的感覺神經細胞，會使原先單獨激發他們時所造成的迎趨行為消失。而當我們把一部分嗅球間的局部神經細胞神經傳導切斷，再同時激發DM6及VA6兩顆嗅小球的感覺神經細胞，果蠅的迎趨行為又會再現。這些實驗結果顯示在氣味訊號進入果蠅嗅覺神經系統後，嗅小球之間的訊息互動是影響果蠅行為很重要的因素。

Reference
Bi, A., Cui, J., Ma, Y.P., Olshevskaya, E., Pu, M., Dizhoor, A.M., and Pan, Z.H. (2006). Ectopic expression of a microbial-type rhodopsin restores visual responses in mice with photoreceptor degeneration. Neuron 50, 23-33.
Boyden, E.S., Zhang, F., Bamberg, E., Nagel, G., and Deisseroth, K. (2005). Millisecond-timescale, genetically targeted optical control of neural activity. Nat Neurosci 8, 1263-1268.
Callaway, E.M., and Yuste, R. (2002). Stimulating neurons with light. Curr Opin Neurobiol 12, 587-592.
Couto, A., Alenius, M., and Dickson, B.J. (2005). Molecular, anatomical, and functional organization of the Drosophila olfactory system. Curr Biol 15, 1535-1547.
Dubnau, J., Grady, L., Kitamoto, T., and Tully, T. (2001). Disruption of neurotransmission in Drosophila mushroom body blocks retrieval but not acquisition of memory. Nature 411, 476-480.
Fishilevich, E., and Vosshall, L.B. (2005). Genetic and functional subdivision of the Drosophila antennal lobe. Curr Biol 15, 1548-1553.
Hallem, E.A., and Carlson, J.R. (2006). Coding of odors by a receptor repertoire. Cell 125, 143-160.
Hallem, E.A., Ho, M.G., and Carlson, J.R. (2004). The molecular basis of odor coding in the Drosophila antenna. Cell 117, 965-979.
Kateriya, S., Nagel, G., Bamberg, E., and Hegemann, P. (2004). "Vision" in single-celled algae. News Physiol Sci 19, 133-137.
Kawasaki, F., Hazen, M., and Ordway, R.W. (2000). Fast synaptic fatigue in shibire mutants reveals a rapid requirement for dynamin in synaptic vesicle membrane trafficking. Nature neuroscience 3, 859-860.
Kitamoto, T. (2001). Conditional modification of behavior in Drosophila by targeted expression of a temperature-sensitive shibire allele in defined neurons. Journal of neurobiology 47, 81-92.
Lin, H.H., Lai, J.S., Chin, A.L., Chen, Y.C., and Chiang, A.S. (2007). A map of olfactory representation in the Drosophila mushroom body. Cell 128, 1205-1217.
McGuire, S.E., Le, P.T., and Davis, R.L. (2001). The role of Drosophila mushroom body signaling in olfactory memory. Science (New York, NY 293, 1330-1333.
Miesenbock, G. (2004). Genetic methods for illuminating the function of neural circuits. Curr Opin Neurobiol 14, 395-402.
Mombaerts, P., Wang, F., Dulac, C., Chao, S.K., Nemes, A., Mendelsohn, M., Edmondson, J., and Axel, R. (1996). Visualizing an olfactory sensory map. Cell 87, 675-686.
Nagel, G., Brauner, M., Liewald, J.F., Adeishvili, N., Bamberg, E., and Gottschalk, A. (2005). Light activation of channelrhodopsin-2 in excitable cells of Caenorhabditis elegans triggers rapid behavioral responses. Curr Biol 15, 2279-2284.
Nagel, G., Ollig, D., Fuhrmann, M., Kateriya, S., Musti, A.M., Bamberg, E., and Hegemann, P. (2002). Channelrhodopsin-1: a light-gated proton channel in green algae. Science 296, 2395-2398.
Nagel, G., Szellas, T., Huhn, W., Kateriya, S., Adeishvili, N., Berthold, P., Ollig, D., Hegemann, P., and Bamberg, E. (2003). Channelrhodopsin-2, a directly light-gated cation-selective membrane channel. Proc Natl Acad Sci U S A 100, 13940-13945.
Ng, M., Roorda, R.D., Lima, S.Q., Zemelman, B.V., Morcillo, P., and Miesenbock, G. (2002). Transmission of olfactory information between three populations of neurons in the antennal lobe of the fly. Neuron 36, 463-474.
Olsen, S.R., Bhandawat, V., and Wilson, R.I. (2007). Excitatory interactions between olfactory processing channels in the Drosophila antennal lobe. Neuron 54, 89-103.
Olsen, S.R., and Wilson, R.I. (2008). Lateral presynaptic inhibition mediates gain control in an olfactory circuit. Nature 452, 956-960.
Ressler, K.J., Sullivan, S.L., and Buck, L.B. (1994). Information coding in the olfactory system: evidence for a stereotyped and highly organized epitope map in the olfactory bulb. Cell 79, 1245-1255.
Ridge, K.D. (2002). Algal rhodopsins: phototaxis receptors found at last. Curr Biol 12, R588-590.
Schlief, M.L., and Wilson, R.I. (2007). Olfactory processing and behavior downstream from highly selective receptor neurons. Nat Neurosci 10, 623-630.
Schroll, C., Riemensperger, T., Bucher, D., Ehmer, J., Voller, T., Erbguth, K., Gerber, B., Hendel, T., Nagel, G., Buchner, E., et al. (2006). Light-induced activation of distinct modulatory neurons triggers appetitive or aversive learning in Drosophila larvae. Curr Biol 16, 1741-1747.
Scott, K., Brady, R., Jr., Cravchik, A., Morozov, P., Rzhetsky, A., Zuker, C., and Axel, R. (2001). A chemosensory gene family encoding candidate gustatory and olfactory receptors in Drosophila. Cell 104, 661-673.
Shang, Y., Claridge-Chang, A., Sjulson, L., Pypaert, M., and Miesenbock, G. (2007). Excitatory local circuits and their implications for olfactory processing in the fly antennal lobe. Cell 128, 601-612.
Sineshchekov, O.A., Jung, K.H., and Spudich, J.L. (2002). Two rhodopsins mediate phototaxis to low- and high-intensity light in Chlamydomonas reinhardtii. Proc Natl Acad Sci U S A 99, 8689-8694.
Stocker, R.F. (1994). The organization of the chemosensory system in Drosophila melanogaster: a review. Cell Tissue Res 275, 3-26.
Suh, G.S., Ben-Tabou de Leon, S., Tanimoto, H., Fiala, A., Benzer, S., and Anderson, D.J. (2007). Light activation of an innate olfactory avoidance response in Drosophila. Curr Biol 17, 905-908.
Suh, G.S., Wong, A.M., Hergarden, A.C., Wang, J.W., Simon, A.F., Benzer, S., Axel, R., and Anderson, D.J. (2004). A single population of olfactory sensory neurons mediates an innate avoidance behaviour in Drosophila. Nature 431, 854-859.
Suzuki, T., Yamasaki, K., Fujita, S., Oda, K., Iseki, M., Yoshida, K., Watanabe, M., Daiyasu, H., Toh, H., Asamizu, E., et al. (2003). Archaeal-type rhodopsins in Chlamydomonas: model structure and intracellular localization. Biochem Biophys Res Commun 301, 711-717.
Tully, T., and Quinn, W.G. (1985). Classical conditioning and retention in normal and mutant Drosophila melanogaster. J Comp Physiol [A] 157, 263-277.
Vassar, R., Chao, S.K., Sitcheran, R., Nunez, J.M., Vosshall, L.B., and Axel, R. (1994). Topographic organization of sensory projections to the olfactory bulb. Cell 79, 981-991.
Vosshall, L.B., Wong, A.M., and Axel, R. (2000). An olfactory sensory map in the fly brain. Cell 102, 147-159.
Waddell, S., Armstrong, J.D., Kitamoto, T., Kaiser, K., and Quinn, W.G. (2000). The amnesiac gene product is expressed in two neurons in the Drosophila brain that are critical for memory. Cell 103, 805-813.
Wang, J.W., Wong, A.M., Flores, J., Vosshall, L.B., and Axel, R. (2003). Two-photon calcium imaging reveals an odor-evoked map of activity in the fly brain. Cell 112, 271-282.
Wilson, R.I., and Laurent, G. (2005). Role of GABAergic inhibition in shaping odor-evoked spatiotemporal patterns in the Drosophila antennal lobe. J Neurosci 25, 9069-9079.