Cell assembly sequences arising from spike threshold adaptation keep track of time in the hippocampus

Vladimir Itskov, Carina Curto, Eva Pastalkova, György Buzsáki

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Abstract

Hippocampal neurons can display reliable and long-lasting sequences of transient firing patterns, even in the absence of changing external stimuli. We suggest that time-keeping is an important function of these sequences, and propose a network mechanism for their generation. We show that sequences of neuronal assemblies recorded from rat hippocampal CA1 pyramidal cells can reliably predict elapsed time (15-20 s) during wheel running with a precision of 0.5 s. In addition, we demonstrate the generation of multiple reliable, long-lasting sequences in a recurrent network model. These sequences are generated in the presence of noisy, unstructured inputs to the network, mimicking stationary sensory input. Identical initial conditions generate similar sequences, whereas different initial conditions give rise to distinct sequences. The key ingredients responsible for sequence generation in the model are threshold-adaptation and a Mexican-hat-like pattern of connectivity among pyramidal cells. This pattern may arise from recurrent systems such as the hippocampal CA3 region or the entorhinal cortex.Wehypothesize that mechanisms that evolved for spatial navigation also support tracking of elapsed time in behaviorally relevant contexts.

Original languageEnglish (US)
Pages (from-to)2828-2834
Number of pages7
JournalJournal of Neuroscience
Volume31
Issue number8
DOIs
StatePublished - Feb 23 2011

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All Science Journal Classification (ASJC) codes

  • Neuroscience(all)

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