Role of Hippocampal CA2 Region in Triggering Sharp-Wave Ripples.
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.
MTA-SZTE "Momentum" Oscillatory Neuronal Networks Research Group, Department of Physiology, University of Szeged, Szeged 6720, Hungary.
Azahara
A
Oliva
MTA-SZTE "Momentum" Oscillatory Neuronal Networks Research Group, Department of Physiology, University of Szeged, Szeged 6720, Hungary; School of Physics, Complutense University, 28040 Madrid, Spain.
Antonio
A
Fernández-Ruiz
New York University Neuroscience Institute and Center for Neural Science, New York University, New York, NY 10016, USA. Electronic address: gyorgy.buzsaki@nyumc.org.
György
G
Buzsáki
MTA-SZTE "Momentum" Oscillatory Neuronal Networks Research Group, Department of Physiology, University of Szeged, Szeged 6720, Hungary; New York University Neuroscience Institute and Center for Neural Science, New York University, New York, NY 10016, USA. Electronic address: drberenyi@gmail.com.
Antal
A
Berényi
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D056547:CA1 Region, Hippocampal / Q000502:physiology; D056651:CA2 Region, Hippocampal / Q000502:physiology*; D056654:CA3 Region, Hippocampal / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D051381:Rats; D012890:Sleep / Q000502:physiology; D014851:Wakefulness / Q000502:physiology
CA1; CA2; CA3; LFP; high-frequency; hippocampus; large-scale recordings; learning; memory consolidation; network mechanism; ripple; sharp-wave; single-unit