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Front. Cell. Neurosci. | doi: 10.3389/fncel.2019.00232

Hippocampal Sequences During Exploration: Mechanisms and Functions

Céline Drieu1, 2, 3, 4* and  Michael Zugaro1, 2, 3, 4*
  • 1Collège de France, France
  • 2Centre National de la Recherche Scientifique (CNRS), France
  • 3Institut National de la Santé et de la Recherche Médicale (INSERM), France
  • 4Université de Sciences Lettres de Paris, France

Although the hippocampus plays a critical role in spatial and episodic memories, the mechanisms underlying memory formation, stabilization, and recall for adaptive behavior remain relatively unknown. During exploration, within single cycles of the ongoing theta rhythm that dominates hippocampal local field potentials, place cells form precisely ordered sequences of activity. These neural sequences result from the integration of both external inputs conveying sensory-motor information, and intrinsic network dynamics possibly related to memory processes. Their endogenous replay during subsequent sleep is critical for memory consolidation. The present review discusses possible mechanisms and functions of hippocampal theta sequences during exploration. We present several lines of evidence suggesting that these neural sequences play a key role in information processing and support the formation of initial memory traces, and discuss potential functional distinctions between neural sequences emerging during theta versus awake sharp-wave ripples.

Keywords: Place Cells, theta, phase precession, Sequences, ripples

Received: 09 Nov 2018; Accepted: 08 May 2019.

Edited by:

Francesca Cacucci, University College London, United Kingdom

Reviewed by:

Romain Goutagny, UMR7364 Laboratoire de Neurosciences Cognitives et Adaptatives (LNCA), France
Caswell Barry, University College London, United Kingdom  

Copyright: © 2019 Drieu and Zugaro. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Dr. Céline Drieu, Collège de France, Paris, France,
Dr. Michael Zugaro, Collège de France, Paris, France,