Thu, 24 Jul 2008 23:46:46 BST CiteULike: awooga's Tsodyks http://www.citeulike.org/user/awooga/author/Tsodyks CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/awooga/article/2531838 <i>Science, Vol. 319, No. 5869. (14 March 2008), pp. 1543-1546.</i><br /><br />It is usually assumed that enhanced spiking activity in the form of persistent reverberation for several seconds is the neural correlate of working memory. Here, we propose that working memory is sustained by calcium-mediated synaptic facilitation in the recurrent connections of neocortical networks. In this account, the presynaptic residual calcium is used as a buffer that is loaded, refreshed, and read out by spiking activity. Because of the long time constants of calcium kinetics, the refresh rate can be low, resulting in a mechanism that is metabolically efficient and robust. The duration and stability of working memory can be regulated by modulating the spontaneous activity in the network. 10.1126/science.1150769 Synaptic Theory of Working Memory Gianluigi Mongillo Omri Barak Misha Tsodyks doi:10.1126/science.1150769 Science, Vol. 319, No. 5869. (14 March 2008), pp. 1543-1546. 2008-03-14T12:03:46-00:00 2008 Science 319 5869 1543 1546 depression facilitation model working-memory http://www.citeulike.org/user/awooga/article/1267984 <i>Neural Comput, Vol. 10, No. 4. (15 May 1998), pp. 821-835.</i><br /><br />Transmission across neocortical synapses depends on the frequency of presynaptic activity (Thomson & Deuchars, 1994). Interpyramidal synapses in layer V exhibit fast depression of synaptic transmission, while other types of synapses exhibit facilitation of transmission. To study the role of dynamic synapses in network computation, we propose a unified phenomenological model that allows computation of the postsynaptic current generated by both types of synapses when driven by an arbitrary pattern of action potential (AP) activity in a presynaptic population. Using this formalism, we analyze different regimes of synaptic transmission and demonstrate that dynamic synapses transmit different aspects of the presynaptic activity depending on the average presynaptic frequency. The model also allows for derivation of mean-field equations, which govern the activity of large, interconnected networks. We show that the dynamics of synaptic transmission results in complex sets of regular and irregular regimes of network activity. Neural networks with dynamic synapses. M Tsodyks K Pawelzik H Markram Neural Comput, Vol. 10, No. 4. (15 May 1998), pp. 821-835. 2007-04-30T13:50:23-00:00 1998 Neural Comput 0899-7667 10 4 821 835 model short-term-depression short-term-facilitation