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Inhibition is the Hallmark of CA3 Intracellular Dynamics Around Awake Ripples


Kajikawa, Koichiro (2022) Inhibition is the Hallmark of CA3 Intracellular Dynamics Around Awake Ripples. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/pwh5-7229.


Hippocampal ripples are transient population bursts that structure cortico-hippocampal communication and play a central role in memory processing. However, the mechanisms controlling ripple initiation in behaving animals remain poorly understood. Here we combine multisite extracellular and whole cell recordings in awake mice to contrast the brain state and ripple modulation of subthreshold dynamics across hippocampal subfields. We find that entorhinal input to DG exhibits UP and DOWN dynamics with ripples occurring exclusively in UP states. While elevated cortical input in UP states generates depolarization in DG and CA1, it produces persistent hyperpolarization in CA3 neurons. Furthermore, growing inhibition is evident in CA3 throughout the course of the ripple buildup, while DG and CA1 neurons exhibit depolarization transients 100 ms before and during ripples. These observations highlight the importance of CA3 inhibition for ripple generation, while pre-ripple responses indicate a long and orchestrated ripple initiation process in the awake state.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Hippocampus, Recurrent Network, CA3, Ripples, Whole-Cell Patch-Clamp Recording, Membrane Potential, Local Field Potential, Inhibition
Degree Grantor:California Institute of Technology
Division:Biology and Biological Engineering
Major Option:Computation and Neural Systems
Minor Option:Computational Science and Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Siapas, Athanassios G.
Thesis Committee:
  • Dickinson, Michael H. (chair)
  • Andersen, Richard A.
  • Hong, Elizabeth J.
  • Siapas, Athanassios G.
Defense Date:19 May 2022
Non-Caltech Author Email:koichirokajikawa (AT)
Record Number:CaltechTHESIS:05272022-195420095
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Ch. 1-4
Kajikawa, Koichiro0000-0002-8626-4407
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14641
Deposited By: Koichiro Kajikawa
Deposited On:02 Jun 2022 19:57
Last Modified:09 Jun 2022 19:49

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