Differential processing through distinct network properties in two parallel olfactory pathways
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1
Freie Universitat Berlin, Institute for Biology - Neurobiology, Germany
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2
Tohoku University, Graduate School of Life Sciences, Japan
In the honeybee olfactory system sensory information is first processed in the antennal lobe before it is relayed to the mushroom body where multimodal information is integrated. Projection neurons (PNs) send their axons from the antennal lobe to the mushroom body via two parallel pathways, the lateral and the medial antenno-cerebral tract (l- and m-ACT). We recorded Ca2+ -activity in presynaptic boutons of PNs in the mushroom body in order to characterize the coding strategies in both pathways. We found that m-ACT PNs exhibit broad odor tuning and strong concentration dependence, i.e. they responded to many of the tested odorants and their responses increased with increasing odor concentration. In contrast, PNs in the l-ACT showed narrow odor tuning and weak concentration dependence, responding only to few odors and only weakly varying with odor concentration [1].
Since PNs of the two tracts innervate glomeruli which are clearly segregated in the antennal lobe, it is possible that these glomeruli belong to partially segregated local networks. We hypothesized that their differential functional characteristics could emerge from distinct network properties in the two pathways. Using a mean-field model of the antennal lobe [2] we could reproduce narrow and broad odor tuning by using simply varying the amount of lateral inhibition in the antennal lobe. Increasing the amount of lateral inhibition led to increasingly narrow odor tuning. In addition, we used gain control by inhibitory feedback to mimic the situation in the presynaptic boutons of PNs, which receive reciprocal inhibitory connections from their downstream targets. Increasing the amount of gain control resulted in less concentration dependence.
Our results suggest that the different coding properties in the l- and m-ACT could emerge from different network properties in those pathways. Our model predicts that the m-ACT network exhibits weak lateral inhibition and weak gain control, leading to broad odor tuning and strong concentration dependence, while the l-ACT network shows strong lateral inhibition and strong gain control, which leads to narrow odor tuning and weak concentration dependence.
References
1. Yamagata N, Schmuker M, Szyszka, Mizunami M and Menzel R (2009): Differential odor processing in two olfactory pathways in the honeybee. Under review.
2. Schmuker M and Schneider G (2007): Processing and classification of chemical data inspired by the sense of smell. PNAS 104:20285-20289.
Conference:
Bernstein Conference on Computational Neuroscience, Frankfurt am Main, Germany, 30 Sep - 2 Oct, 2009.
Presentation Type:
Poster Presentation
Topic:
Information processing in neurons and networks
Citation:
Schmuker
M,
Yamagata
N and
Menzel
R
(2009). Differential processing through distinct network properties in two parallel olfactory pathways.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference on Computational Neuroscience.
doi: 10.3389/conf.neuro.10.2009.14.072
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Received:
26 Aug 2009;
Published Online:
26 Aug 2009.
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Correspondence:
Michael Schmuker, Freie Universitat Berlin, Institute for Biology - Neurobiology, 82152 Planegg-Martinsried, Germany, m.schmuker@biomachinelearning.net