Hippocampus as a sorter and reverberatory integrator of sensory inputs

How the hippocampus sorts and integrates multiple sensory inputs during learning remains unclear. Here, the authors found that the hippocampus uses reverberatory activity to link conditioned and unconditioned stimuli and to avoid crosstalk during sensory inputs. The hippocampus must be capable of sorting and integrating multiple sensory inputs separately but simultaneously. However, it remains to be elucidated how the hippocampus executes these processes simultaneously during learning. Here we found that synchrony between conditioned stimulus (CS)-, unconditioned stimulus (US)- and future retrieval-responsible cells occurs in the CA1 during the reverberatory phase that emerges after sensory inputs have ceased, but not during CS and US inputs. Mutant mice lacking N-methyl-D-aspartate receptors (NRs) in CA3 showed a cued-fear memory impairment and a decrease in synchronized reverberatory activities between CS- and US-responsive CA1 cells. Optogenetic CA3 silencing at the reverberatory phase during learning impaired cued-fear memory. Thus, the hippocampus uses reverberatory activity to link CS and US inputs, and avoid crosstalk during sensory inputs.

Automated summary

The hippocampus utilizes reverberatory activity to link conditioned and unconditioned stimuli and avoid interference during sensory inputs. It is still unknown how the hippocampus executes these processes simultaneously during learning.