Event Abstract Back to Event A model of vPFC neurons performing a same-different task: an alternative model of working memory Jung Lee1* and Yale Cohen2 1 University of Pennsylvania School of Medicine, Department of Otorhinolaryngology, United States 2 University of Pennsylvania School of Medicine, United States Working memory is a fundamental component of cognition. Classically, the neural correlates of working memory is thought to involve persistent or sustained activity that is mediated by strongly recurrently connected groups of neurons. Recently, we recorded from neurons in the ventrolateral prefrontal cortex (vPFC), while monkeys reported whether sequentially presented auditory stimuli were the same or different and found that vPFC neural activity is predictive of the monkeys’ decisions. Since this task required the monkeys to compare sequential stimuli, vPFC neurons should have access to a memory trace of the previous stimulus. However, we could not identify such a trace (i.e., persistent activity) in the firing rates of vPFC neurons between stimulus presentation nor could we identify a memory trace in neurons of the superior temporal gyrus (STG), a cortical region which projects to the vPFC. Instead, we found that memory traces appeared to be stored in the local-field potentials (LFPs) of the vPFC. Here, we present a model of the vPFC that incorporates both LFPs (membrane potentials) and spiking activity. This circuit has three layers: an input, middle, and output layer; the output layer is the read-out layer. The middle layer contains two groups of neurons each of which is tuned to a different stimulus and a third group which is "untuned". The two tuned neural groups are also bilaterally connected with a group of inhibitory inter-neurons. All of the synaptic weights are static except for the synapses between the tuned neurons and the inter-neurons and the untuned neurons and the output (read-out neurons). These dynamic synapses are updated by a simple rule that captures only qualitative properties of realistic dynamic synapses as proposed by Tsodyks et al.: action potentials potentiate the synapse; otherwise, it is depressed. As a consequence of this architecture, a negative feedback loop is established between the tuned neurons and the inter-neurons. When the same stimulus is presented sequentially, this feedback loop suppresses activity in those neurons that are tuned to this stimulus, but it does not affect the activity levels in the other tuned group. Consequently, when a different stimulus is presented, the responses of these neurons are robust. As a result, this circuit can discriminate between sequential stimuli. Furthermore, due to the connectivity of the untuned neural group, the spiking activity of the output neurons (1) does not habituate when the same stimulus is presented sequentially and (2) is enhanced when a different stimulus is presented. Whereas the spiking activity does not habituate, an analysis of the network’s membrane potential indicates that the average membrane potential does habituate. This overall pattern of spiking activity and membrane-potential changes mimics that seen in our vPFC data. It is possible to build a circuit-level model of working memory based on dynamic synapses that does not produce persistent activity. This model raises the possibility of alternative mechanisms underlying working memory. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session III Citation: Lee J and Cohen Y (2010). A model of vPFC neurons performing a same-different task: an alternative model of working memory. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00232 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Mar 2010; Published Online: 04 Mar 2010. * Correspondence: Jung Lee, University of Pennsylvania School of Medicine, Department of Otorhinolaryngology, Philadelphia, United States, jleeh@mail.med.upenn.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Jung Lee Yale Cohen Google Jung Lee Yale Cohen Google Scholar Jung Lee Yale Cohen PubMed Jung Lee Yale Cohen Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.
Read full abstract