Pattern Separation in the Dentate Gyrus
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1
University of California San Diego, Neurobiology Section, Division of Biological Sciences, United States
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2
Norwegian University of Science and Technology, Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory, Norway
Storing a large number of distinct neuronal representations requires that the input patterns to a memory network are distinct. When sensory inputs are similar, this can be achieved by a neuronal processing stage that amplifies small differences, a process that is defined as pattern separation. Theoretical models have long pointed to the dentate gyrus as a possible source of neuronal pattern separation. We investigated the role of the dentate gyrus in these computations by recording neuronal activity patterns from dentate neurons and their downstream targets, the CA3 pyramidal neurons, under conditions in which either the spatial location or features surrounding a single location were varied. At two separate locations, the firing patterns in the CA3 area were maximally distinct. This was achieved by activating two separate cell populations. In simultaneously recorded dentate cells, it was found that the same small subset of dentate cells remained active. Pattern separation was therefore more pronounce in CA3 than in the dentate. When recording cells while changing sensory cues surrounding a single location, it was found that the same CA3 cell population remained active. Pattern separation in the dentate gyrus was again achieved by decorrelating the rate distribution in a small subset of active granule cells rather than by the activation of distinct cell assemblies. Since the firing patterns in CA3 were now less distinct, the pattern separation in the dentate gyrus exceeded the levels that were found in the other hippocampal subregions. During the latter conditions, the lateral entorhinal cortex has a more pronounced role in supporting hippocampal pattern separation. We therefore suggest that the direct input from the dentate gyrus to the CA3 network is important for the rapid acquisition of novel information, in particular when there are only small input differences within a constant spatial framework.
Supported by a Norw. Res. Council Ctr. of Excellence Grant.
Conference:
41st European Brain and Behaviour Society Meeting, Rhodes Island, Greece, 13 Sep - 18 Sep, 2009.
Presentation Type:
Oral Presentation
Topic:
Symposia lectures
Citation:
Leutgeb
JK,
Leutgeb
S,
Britt-Moser
M and
Moser
EI
(2009). Pattern Separation in the Dentate Gyrus.
Conference Abstract:
41st European Brain and Behaviour Society Meeting.
doi: 10.3389/conf.neuro.08.2009.09.033
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Received:
04 Jun 2009;
Published Online:
04 Jun 2009.
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Correspondence:
Jill K Leutgeb, University of California San Diego, Neurobiology Section, Division of Biological Sciences, La Jolla, United States, jleutgeb@ucsd.edu