Networks with continuous set of attractors are considered to be a paradigmatic model for parametric working memory (WM), but require fine tuning of connections and are thus structurally unstable. Here we analyzed the network with ring attractor, where connections are not perfectly tuned and the activity state therefore drifts in the absence of the stabilizing stimulus. We derive an analytical expression for the drift dynamics and conclude that the network cannot function as WM for a period of several seconds, a typical delay time in monkey memory experiments. We propose that short-term synaptic facilitation in recurrent connections significantly improves the robustness of the model by slowing down the drift of activity bump. Extending the calculation of the drift velocity to network with synaptic facilitation, we conclude that facilitation can slow down the drift by a large factor, rendering the network suitable as a model of WM.
Keywords: parametric working memory, continuous attractors, synaptic facilitation, Ring model, bump attractor, working memory, inhomogeneous neural media, neural fields
Citation: Itskov V, Hansel D and Tsodyks M (2011) Short-term facilitation may stabilize parametric working memory trace. Front. Comput. Neurosci. 5:40. doi: 10.3389/fncom.2011.00040
Received: 22 January 2011; Paper pending published: 17 March 2011;
Accepted: 08 September 2011; Published online: 24 October 2011.
Edited by:Stefano Fusi, Columbia University, USA
Reviewed by:Albert Compte, Institut d ′Investigacions Biomèdiques August Pi i Sunyer, Spain
Copyright: © 2011 Itskov, Hansel and Tsodyks. This is an open-access article subject to a non-exclusive license between the authors and Frontiers Media SA, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and other Frontiers conditions are complied with.
*Correspondence: Vladimir Itskov, Department of Mathematics, University of Nebraska-Lincoln, 244 Avery Hall, Lincoln, NE 68588, USA. e-mail: firstname.lastname@example.org