Role of Hippocampal CA2 Region in Triggering Sharp-Wave Ripples

Neuron. 2016 Sep 21;91(6):1342-1355. doi: 10.1016/j.neuron.2016.08.008. Epub 2016 Sep 1.


Sharp-wave ripples (SPW-Rs) in the hippocampus are implied in memory consolidation, as shown by observational and interventional experiments. However, the mechanism of their generation remains unclear. Using two-dimensional silicon probe arrays, we investigated the propagation of SPW-Rs across the hippocampal CA1, CA2, and CA3 subregions. Synchronous activation of CA2 ensembles preceded SPW-R-related population activity in CA3 and CA1 regions. Deep CA2 neurons gradually increased their activity prior to ripples and were suppressed during the population bursts of CA3-CA1 neurons (ramping cells). Activity of superficial CA2 cells preceded the activity surge in CA3-CA1 (phasic cells). The trigger role of the CA2 region in SPW-R was more pronounced during waking than sleeping. These results point to the CA2 region as an initiation zone for SPW-Rs.

Keywords: CA1; CA2; CA3; LFP; high-frequency; hippocampus; large-scale recordings; learning; memory consolidation; network mechanism; ripple; sharp-wave; single-unit.

MeSH terms

  • Action Potentials / physiology
  • Animals
  • CA1 Region, Hippocampal / physiology
  • CA2 Region, Hippocampal / physiology*
  • CA3 Region, Hippocampal / physiology
  • Neural Pathways / physiology
  • Rats
  • Sleep / physiology
  • Wakefulness / physiology