Most hippocampal CA1 pyramidal cells in rabbits increase firing during awake sharp-wave ripples and some do so in response to external stimulation and theta

Abstract

We studied hippocampal sharp-wave ripples and theta and CA1 pyramidal cell activity during trace eyeblink conditioning in rabbits. Conditioning trials suppressed ripples while increasing theta for a period of several seconds. A quarter of the cells increased firing in response to the conditioned stimulus and fired extensively during endogenous theta as well as ripples. The role of endogenous theta epochs in off-line memory consolidation should be studied further.

Normal and Abnormal Sharp Wave Ripples in the Hippocampal-Entorhinal Cortex System: Implications for Memory Consolidation, Alzheimer's Disease, and Temporal Lobe Epilepsy

“…Further, concurrent SWRs can induce synaptic potentiation between neurons in vivo , resulting in stronger functional coupling and SWRs coherence (King et al, 1999 ). In animal models, including rats and macaques, such coincident SWRs among neuronal populations are observed during quiet immobility and sleep as well as during consummatory behavior, grooming, brief interruptions in locomotion, and even during active visual exploration (O'Neill et al, 2006 ; Cowen et al, 2020 ; Hussin et al, 2020 ; Nokia et al, 2020 ; Sosa et al, 2020 ).…”