Spike timing dependent plasticity

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Spike timing dependent plasticity (STDP) is a form of synaptic plasticity naturally occurring in neurons. This form of plasticity refers to the rules that relate the timing of pre- and post-synaptic neuronal activity and changes in the strength of the synaptic connection between pre- and post-synaptic neurons.

Contents 1 History 2 From Hebbian Rule to STDP 3 See Also 4 External links

[edit] History

The first experiments that specifically examined the effect of millisecond relative timing of pre and postsynaptic action potentials was carried out by Henry Markram in Bert Sakmann's laboratory in 1994. [Infact, one of the very first experimental observations on the phenomenon of STDP (though its not sure if this terminology was being thought of at that point) was performed by Dominique Debanne (Proc Natl Acad Sci U S A. 1994 Feb 1;91(3):1148-52.) where they showed Asynchronous pre- and postsynaptic activity induces associative long-term depression in area CA1 of the rat hippocampus in vitro.] Coming back to Henry Markram's experiments, using dual patch clamping techniques, they repetitively activated pre-synaptic neurons 10 milliseconds before post-synaptic target neurons, and found the strength of the synapse increased. When the activation order was reversed so that the pre-synaptic neuron was activated 10 milliseconds after its post-synaptic target neuron, the strength of the pre-to-post synaptic connection decreased. Further work, first by Li Zhang and Mu Ming Poo in 1998, mapped the entire time course relating pre- and post-synaptic activity and synpatic change, to show that in their prep synapses that are activated within 5-40 ms before a postsynaptic spike are strengthen, and those that are activated within a similar time window after the spike are weakened. This phenomenon has been observed in various other preparations, with some variation in the time-window relevant for plasticity. Several reasons for timing-dependent plasticity have been suggested. For example, STDP might operate as a learning rule that maximizes the mutual information between inputs and outputs of simple networks.

[edit] From Hebbian Rule to STDP

According to the Hebbian Rule synapses increase their efficacy if the synapse persistently causes the postsynaptic target neuron to generate action potentials. An often used but not entirely accurate simplification is those who fire together, wire together. With recent advancements in technology we can more precisely measure the spike timing of neurons. As it turns out, the synaptic connection between two neurons is more likely to strengthen if the presynaptic neuron fires off shortly before the postsynaptic neuron. Revisiting, the Hebbian rule, we can tweak it to accommodate the new model. Synapses increase their efficacy if the presynaptic neuron is activated momentarily before the postsynaptic neuron is activated. OR Synapses in which the pre-synaptic input fired before the postsynaptic cell get stronger; in the inverse situation, the synapse gets weaker.

[edit] See Also

Synaptic plasticity

[edit] External links

• Rumsey C.C., Abbott L.F. Equalization of Synaptic Efficacy by Activity- and Time- Dependent Synaptic Plasticity. J Neurophysiol 91: 2273-2280, 2004.

• Debanne D, Gahwiler BH, Thompson SM.

Asynchronous pre- and postsynaptic activity induces associative long-term depression in area CA1 of the rat hippocampus in vitro. Proc Natl Acad Sci U S A. 1994 Feb 1;91(3):1148-52. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=7905631&query_hl=2&itool= pubmed_DocSum]

• Markram H., Lubke J., Frotscher M., Sakmann B. Regulation of synaptic efficacy by coincidence of postsynaptic APs and EPSPs. Science 275, 213-5 (1997)

• Bi G.Q., Poo M.M. Synaptic modifications in cultured hippocampal neurons: dependence on spike timing, synaptic strength, and postsynaptic cell type. Journal of Neuroscience 18, 10464-72 (1998)

• Sjostrom PJ, Turrigiano GG, Nelson SB Rate, timing, and cooperativity jointly determine cortical synaptic plasticity Neuron 2001 Dec 20;32(6):1149-64

• Senn W., Markram H., Tsodyks M.; An algorithm for Modifying Neurotransmitter Release Probability Based on Pre- and Postsynaptic Spike Timing. Neural Computation 13, 35-67 (2000)

• Roberts P.D., Bell C.C. ; Spike-timing dependent synaptic plasticity in biological systems. Biological Cybernetics, 87, 392-403 (2002)

• Chechik G.; Spike Time dependent plasticity and relevant information maximization. Neural Computation 15(7) p.1481-1510, (2003)

• Lisman J., Spruston N.; Postsynaptic depolarization requirements for LTP and LTD: a critique of spike timing-dependent plasticity. Nature Neuroscience' 8, 839-41 (2005)