- Poster Presentation
- Open Access
The effect of synaptic plasticity on the stability of place fields under graded environmental perturbations
© Ward et al; licensee BioMed Central Ltd. 2010
- Published: 20 July 2010
- Grid Cell
- Synaptic Plasticity
- Hippocampal Cell
- Environmental Perturbation
- Place Field
We developed a parallel computational model of a network of entorhinal and hippocampal cells influenced by synaptic plasticity to examine the stability of CA3 place fields under graded environmental perturbations. Place cells form single firing fields within an environment and are located in the CA1 and CA3 subregions of the hippocampus. They receive the majority of their spatial input from grid cells, which are located in the medial entorhinal cortex (MEC) and fire in hexagonal patterns within an environment .
We designed the model in the context of the “double rotation” experiment in which a rat circles a track with various local and distal cues that are rotated in opposite directions. In response to this rotation, some CA1 cells follow local cues, some follow distal cues, and some remap. In contrast, CA3 place fields are more coherently dominated by local cues . This CA3 response is puzzling given that grid cells are more strongly controlled by distal cues . Because local cues were rotated in a direction opposite to the rat’s movement, the backward shift of place fields  may affect the CA3 response. Cells in the lateral entorhinal cortex (LEC) show a slight tendency to follow local cues , and we used the model to investigate whether the backward shift couples with weak LEC input to cause CA3 cells to rotate with the local cues.
In the model the MEC contains grid cells, and LEC cells are weakly tuned to local cues. CA1 and CA3 cells are governed by the integrate and fire model, which provides no bias for spiking at one location over another. Rate-based plasticity  applied to the connections from grid cells to hippocampal cells enables place fields to form, and spike-timing-dependent plasticity  applied to the connections among CA3 cells enables place fields to shift backward, as seen experimentally.
We implemented the model in PETSc (Portable, Extensible Toolkit for Scientific Computation), a suite of data structures and routines for parallel computation. This implementation greatly increased both the number of tractable variables and the speed of computation. We simulated networks of up to 20,000 cells, and the computational time reduces by a factor of 15 as we move from one processor to 64 processors. Because the model is efficient, modular, and capable of simulating large networks, it is an efficient tool for examining the effect of synaptic plasticity on place field dynamics.
- Hafting T, Fyhn M, Molden S, Moser M, Moser E: Microstructure of a spatial map in the entorhinal cortex. Nature. 2005, 436: 801-806. 10.1038/nature03721.View ArticlePubMedGoogle Scholar
- Lee I, Yoganarasimha D, Rao G, Knierim J: Comparison of population coherence of place cells in hippocampal subfields CA1 and CA3. Nature. 2004, 430: 456-459. 10.1038/nature02739.View ArticlePubMedGoogle Scholar
- Neunuebel J, Rao G, Yoganarasimha D, Knierim J: Differential control of lateral and medial entorhinal cortex by local and global cues. Program No. 100.4. 2009 Neuroscience Meeting Planner. Chicago, IL: Society of Neuroscience. 2009, OnlineGoogle Scholar
- Mehta MR, Barnes CA, McNaughton BL: Experience-dependent, asymmetric expansion of hippocampal place fields. Proc Natl Acad Sci U S A. 1997, 94: 8918-8921. 10.1073/pnas.94.16.8918.PubMed CentralView ArticlePubMedGoogle Scholar
- Savelli F, Knierim J: A Hebbian model of the formation of place fields from MEC grid inputs. Program No. 205.21. 2007 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience. 2007, OnlineGoogle Scholar
- Song S, Miller K, Abbott L: Competitive Hebbian learning through spike-timing-dependent synaptic plasticity. Nature Neuroscience. 2000, 3: 919-926. 10.1038/78829.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd.