Gabbiani, Fabrizio and Krapp, Holger G. and Koch, Christof and Laurent, Gilles (2002) Multiplicative computation in a visual neuron sensitive to looming. Nature, 420 (6913). pp. 320-324. ISSN 0028-0836. http://resolver.caltech.edu/CaltechAUTHORS:20130816-103254436
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Multiplicative operations are important in sensory processing, but their biophysical implementation remains largely unknown. We investigated an identified neuron (the lobula giant movement detector, LGMD, of locusts) whose output firing rate in response to looming visual stimuli has been described by two models, one of which involves a multiplication. In this model, the LGMD multiplies postsynaptically two inputs (one excitatory, one inhibitory) that converge onto its dendritic tree; in the other model, inhibition is presynaptic to the LGMD. By using selective activation and inactivation of pre- and postsynaptic inhibition, we show that postsynaptic inhibition has a predominant role, suggesting that multiplication is implemented within the neuron itself. Our pharmacological experiments and measurements of firing rate versus membrane potential also reveal that sodium channels act both to advance the response of the LGMD in time and to map membrane potential to firing rate in a nearly exponential manner. These results are consistent with an implementation of multiplication based on dendritic subtraction of two converging inputs encoded logarithmically, followed by exponentiation through active membrane conductances.
|Additional Information:||© 2002 Nature Publishing Group. Received 1 August 2002; Accepted 20 September 2002. We thank C. Mo for technical assistance with the experiments presented in Fig. 2, S. Potter for help with two-photon confocal microscopy, and J. Maunsell for comments. This work was supported by the Sloan Foundation, the National Institute of Mental Health (F.G., C.K.), the National Institute for Deafness and Communication Disorders (G.L.), the McKnight Foundation (G.L.) and the Center for Neuromorphic Engineering as part of the NSF Engineering Research Center programme. H.G.K. was supported by a travel grant of the Deutsche Forschungsgemeinschaft. F.G. is an Alfred P. Sloan research fellow.|
|Group:||Koch Laboratory, KLAB|
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|Deposited By:||KLAB Import|
|Deposited On:||16 Jan 2008 01:47|
|Last Modified:||20 Nov 2015 01:06|
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