Local projections of layer Vb-to-Va are more effective in lateral than in medial entorhinal cortex

Abstract

SummaryThe entorhinal cortex, in particular neurons in layer V, allegedly mediate transfer of information between the hippocampus and the neocortex, underlying long-term memory. Recently, this circuit has been shown to comprise a hippocampal output recipient layer Vb and a cortical projecting layer Va. With the use of in vitro electrophysiology in transgenic mice specific for layer Vb, we assessed the presence of the thus necessary connection between layer Vb and layer Va in the two functionally distinct medial (MEC) and lateral (LEC) subdivisions; MEC processes allocentric spatial information, whereas LEC represents the content of episodes. Using identical experimental approaches, we show that in LEC, but not in MEC, layer Vb neurons provide substantial direct input to layer Va neurons. This indicates that the hippocampal-cortex output circuit is present only in LEC, suggesting that episodic systems consolidation predominantly uses LEC-derived information and not allocentric spatial information from MEC.

Behavioral pattern separation and cognitive flexibility are enhanced in a mouse model of increased lateral entorhinal cortex-dentate gyrus circuit activity

“…The specific mechanism and circuitry underlying this effect are not tested in the present study. One consideration for future research is that induced stimulation of LECIIa fan cells (which project to the DG) may indirectly alter the activity of LEC cells that project to other brain regions (such as the LECII pyramidal cells or neurons in deep LEC layers projecting to the PFC) or even of MEC cells (Insausti et al, 1997 ; Delatour and Witter, 2002 ; Tanji and Hoshi, 2008 ; Canto and Witter, 2012 ; Ohara et al, 2020 ; Yu et al, 2021 ).…”

Behavioral pattern separation and cognitive flexibility are enhanced in a mouse model of increased lateral entorhinal cortex-dentate gyrus circuit activity

“…However, our data are the first to show a role for the activity of the entorhinal cortex in cognitive flexibility. While the specific mechanism underlying this effect is not tested in the present work, one consideration for future research is that induced stimulation of LECIIa fan cells (which project to the DG) may indirectly alter the activity of LEC cells that project to the PFC, such LECII pyramidal cells or neurons in deep LEC layers, or the activity of MEC cells (Ohara et al;Insausti et al, 1997;Delatour and Witter, 2002;Tanji and Hoshi, 2008;Canto and Witter, 2012;Yu et al, 2021).…”