| Spike-based synaptic plasticity and the emergence of direction selective simple cells: simulation results. | |
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MedLine Citation:
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PMID: 12226559 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Direction selectivity (DS) of simple cells in the primary visual cortex was recently suggested to arise from short-term synaptic depression in thalamocortical afferents (Chance F, Nelson S, Abbott L (1998), J. Neuroscience 18(12): 4785-4799). In the model, two groups of afferents with spatially displaced receptive fields project through either depressing and non-depressing synapses onto the V1 cell. The degree of synaptic depression determines the temporal phase advance of the response to drifting gratings. We show that the spatial displacement and the appropriate degree of synaptic depression required for DS can develop within an unbiased input scenario by means of temporally asymmetric spike-timing dependent plasticity (STDP) which modifies both the synaptic strength and the degree of synaptic depression. Moving stimuli of random velocities and directions break any initial receptive field symmetry and produce DS. Frequency tuning curves and subthreshold membrane potentials akin to those measured for non-directional simple cells are thereby changed into those measured for directional cells. If STDP is such that down-regulation dominates up-regulation the overall synaptic strength adapts in a self-organizing way such that eventually the postsynaptic response for the non-preferred direction becomes subthreshold. To prevent unlearning of the acquired DS by randomly changing stimulus directions an additional learning threshold is necessary. To further protect the development of the simple cell properties against noise in the stimulus, asynchronous and irregular synaptic inputs are required. |
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Authors:
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N J Buchs; W Senn |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Journal of computational neuroscience Volume: 13 ISSN: 0929-5313 ISO Abbreviation: J Comput Neurosci Publication Date: 2002 Nov-Dec |
Date Detail:
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Created Date: 2002-09-12 Completed Date: 2002-12-12 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 9439510 Medline TA: J Comput Neurosci Country: United States |
Other Details:
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Languages: eng Pagination: 167-86 Citation Subset: IM |
Affiliation:
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Physiological Institute, University of Bern, Bühlplatz 5, CH-3012 Bern. buchs@cns.unibe.ch |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Afferent Pathways
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physiology Animals Computer Simulation Learning Models, Neurological* Neuronal Plasticity* Synapses / physiology* Visual Cortex / physiology* |
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