Time cells in the hippocampus are neither dependent on mEC inputs nor necessary for spatial working memory

A key function of the hippocampus and entorhinal cortex is to bridge events that are discontinuous in time, and it has been proposed that mEC supports memory retention by sustaining the sequential activity of hippocampal time cells. We therefore recorded hippocampal neuronal activity during spatial working memory and asked whether time cells depend on mEC inputs. Working memory was impaired in rats with mEC lesions, but the occurrence of time cells and of trajectory-coding cells in the stem did not differ from controls. Rather, the main effect of mEC lesions was an extensive spatial coding deficit of CA1 cells, which included inconsistency over time and reduced firing differences between positions on the maze. MEC is therefore critical for providing stable and distinct spatial information to hippocampus, while WM maintenance is likely supported either by local synaptic plasticity in hippocampus or by activity patterns elsewhere in the brain.