The Journal of Neuroscience, June 4, 2008, 28(23):5959-5964; doi:10.1523/JNEUROSCI.5262-07.2008
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Brief Communications
Theta-Mediated Dynamics of Spatial Information in Hippocampus
Vladimir Itskov,1,2
Eva Pastalkova,1
Kenji Mizuseki,1
Gyorgy Buzsaki,1 and
Kenneth D. Harris1
1Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, Newark, New Jersey 07102, and 2Center for Neurobiology and Behavior, Columbia University, New York, New York 10032
Correspondence should be addressed to Vladimir Itskov, Center for Neurobiology and Behavior, Columbia University, Kolb Annex, Unit 87, Room 762, 1051 Riverside Drive, New York, NY 10032-2695. Email: vi2109{at}columbia.edu
In rodent hippocampus, neuronal activity is organized by a 6–10 Hz theta oscillation. The spike timing of hippocampal pyramidal cells with respect to the theta rhythm correlates with an animal's position in space. This correlation has been suggested to indicate an explicit temporal code for position. Alternatively, it may be interpreted as a byproduct of theta-dependent dynamics of spatial information flow in hippocampus. Here we show that place cell activity on different phases of theta reflects positions shifted into the future or past along the animal's trajectory in a two-dimensional environment. The phases encoding future and past positions are consistent across recorded CA1 place cells, indicating a coherent representation at the network level. Consistent theta-dependent time offsets are not simply a consequence of phase-position correlation (phase precession), because they are no longer seen after data randomization that preserves the phase-position relationship. The scale of these time offsets, 100–300 ms, is similar to the latencies of hippocampal activity after sensory input and before motor output, suggesting that offset activity may maintain coherent brain activity in the face of information processing delays.
Key words: hippocampus; place cells; theta oscillation; phase precession; temporal coding; response latency
Received May 28, 2007;
revised March 18, 2008;
accepted April 14, 2008.
Correspondence should be addressed to Vladimir Itskov, Center for Neurobiology and Behavior, Columbia University, Kolb Annex, Unit 87, Room 762, 1051 Riverside Drive, New York, NY 10032-2695. Email: vi2109{at}columbia.edu
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