Do Morphologically Distinct Projection Neurons in the Honey Bee Antennal Lobe Spike Differently?
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1
Freie Universität Berlin, Germany
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2
Universität Würzburg, Germany
It is widely acknowledged that a neurons function is reflected in both, its morphology and its electro-physiological properties. However it is very difficult to conclude from either of these two characteristics to the other one. In a previous study [1] we employed semi-supervised hierarchical clustering to explore spiking properties which most effectively describe differences between local neurons (LNs) and projection neurons (PNs) in the honey bee antennal lobe (AL).Here we used the same approach to explore differences between two types of PNs. These morphologically similar neuron families leave the AL via different tracts, the lateral (l-APT PNs) and the medial Antenno Protocerebral Tract (m-APT PNs). The existence of these two separated pathways suggests functional differences between its neurons. But is this assumption supported by systematic differences in electrophysiological features? And if so, which features are most helpful to separate m-APT PNs from l-APT PNs?
We analyzed data from 122 extracellularly recorded AL units which, based on electrode placement were unambiguously identified as belonging to the m- or the l-APT [2]. For each unit well established measures of electrophysiological activity were estimated. We explored clustering of units based on the principal components (PCs) of every possible combination of these measures. Using hierarchical clustering with wards-linkage we determined which combination of measures performed best in separating l-APT units and m-APT units from each other. We repeated the same clustering routine on the original data, without prior principal component analysis.
We find that clustering of l-APT units and m-APT units by means of electrophysiological features performs rather poor (~36% above chance level) as compared to cluster results between .LNs and PNs (~81 above chance level). The properties which contributed most to the separation of units from different tracts were the mean evoked rate within a response window, Fano-factor, and a units lifetime sparseness (reflecting odour tuning). Repetition of the analysis without PC-transformation of physiological measures led to the same result, albeit with a reduced classification performance (34% above chance level without vs. 39% with PCA
Electrophysiological properties of units from the l-APT and the m-APT appear far more similar than those of LNs and PNs as a whole. In agreement with our results, many recent experimental findings have repeatedly indicated difficulties to differentiate physiological properties of l-PNs and m-PNs [2, 3, 4].What has been described often a times phenomenologicaly, are differences in odour tuning, firing frequency and sometimes rate profiles. These phenomena are well captured in those features that were identified as best separators: life time sparseness, Fano-factor and evoked Rate. Taken together, our quantitative results seem to confirm the qualitative experience.
Acknowledgements
Funding was received from the German Federal Ministry of Education and Research (BMBF) through grant "01GQ0941" to the Bernstein Focus Neuronal Basis of Learning (BFNL) and the Deutsche Forschungs Gemeinschaft (DFG) SPP 1392 (RO 1177/5-1).
References
[1] Meyer A, Galizia C and Nawrot MP (2011). A spiking point of view - Is it possible to predict a neurons morphology from its electrophysiological activity?.Front. Comput. Neurosci. Conference Abstract: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference.
[2] Brill MF, Meyer A, Nawrot MP and Rössler WJ (2012). Parallel processing within a dual olfactory pathway in the honeybee. Control/Tracking Number: 2012-S-5360-SfN ,
[3] Carcaud J, Hill T, Giurfa M and Sandoz JC (2012). Differential coding by two olfactory subsystems in the honey bee brain. J Neurophysiol. 2012 May 9
[4] Krofczik S, Menzel R and Nawrot MP (2008). Rapid odor processing in the honeybee antennal lobe network. Front Comput Neurosci. 2008;2:9
Keywords:
Electrophysiology,
Hirarchical Clustering,
Honey bee,
projection neurons
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Data analysis, machine learning, neuroinformatics
Citation:
Meyer
A,
Brill
M,
Rössler
W and
Nawrot
MP
(2012). Do Morphologically Distinct Projection Neurons in the Honey Bee Antennal Lobe Spike Differently?.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00096
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Received:
11 May 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Dr. Anneke Meyer, Freie Universität Berlin, Berlin, Germany, anneke.meyer@uni-konstanz.de