Cell-type-specific optogenetic techniques reveal neural circuits crucial for episodic memories

Naoki Yamamoto, William D. Marks, Takashi Kitamura

Research output: Chapter in Book/Report/Conference proceedingChapter

2 Scopus citations


The formation and maintenance of episodic memories are important for our daily life. Accumulating evidence from extensive studies with pharmacological, electrophysiological, and molecular biological approaches has shown that both entorhinal cortex (EC) and hippocampus (HPC) are crucial for the formation and recall of episodic memory. However, to further understand the neural mechanisms of episodic memory processes in the EC-HPC network, cell-type-specific manipulation of neural activity with high temporal resolution during memory process has become necessary. Recently, the technological innovation of optogenetics combined with pharmacological, molecular biological, and electrophysiological approaches has significantly advanced our understanding of the circuit mechanisms for learning and memory. Optogenetic techniques with transgenic mice and/or viral vectors enable us to manipulate the neural activity of specific cell populations as well as specific neural projections with millisecond-scale temporal control during animal behavior. Integrating optogenetics with drug-regulatable activity-dependent gene expression systems has identified memory engram cells, which are a subpopulation of cells that encode a specific episode. Finally, millisecond pulse stimulation of neural activity by optogenetics has further achieved (a) identification of synaptic connectivity between targeted pairs of neural populations, (b) cell-type-specific single-unit electrophysiological recordings, and (c) artificial induction and modification of synaptic plasticity in targeted synapses. In this chapter, we summarize technological and conceptual advancements in the field of neurobiology of learning and memory as revealed by optogenetic approaches in the rodent EC-HPC network for episodic memories.

Original languageEnglish (US)
Title of host publicationAdvances in Experimental Medicine and Biology
Number of pages19
StatePublished - 2021

Publication series

NameAdvances in Experimental Medicine and Biology
ISSN (Print)0065-2598
ISSN (Electronic)2214-8019


  • Entorhinal cortex
  • Episodic memory
  • Hippocampus
  • Memory engram
  • Neural circuit
  • Optogenetics
  • Synaptic plasticity
  • Systems consolidation of memory

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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