Impact of Spikelets on Hippocampal CA1 Pyramidal Cell Activity During Spatial Exploration

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Science  22 Jan 2010:
Vol. 327, Issue 5964, pp. 474-477
DOI: 10.1126/science.1182773

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In vivo intracellular recordings of hippocampal neurons reveal the occurrence of fast events of small amplitude called spikelets or fast prepotentials. Because intracellular recordings have been restricted to anesthetized or head-fixed animals, it is not known how spikelet activity contributes to hippocampal spatial representations. We addressed this question in CA1 pyramidal cells by using in vivo whole-cell recording in freely moving rats. We observed a high incidence of spikelets that occurred either in isolation or in bursts and could drive spiking as fast prepotentials of action potentials. Spikelets strongly contributed to spiking activity, driving ~30% of all action potentials. CA1 pyramidal cell firing and spikelet activity were comodulated as a function of the animal’s location in the environment. We conclude that spikelets have a major impact on hippocampal activity during spatial exploration.

  • * These authors contributed equally to this work.

  • Present address: Howard Hughes Medical Institute, Janelia Farm Research Campus, Ashburn, VA 20147, USA.

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