Distinct speed dependence of entorhinal island and ocean cells, including respective grid cells

Abstract

Entorhinal-hippocampal circuits in the mammalian brain are crucial for an animal's spatial and episodic experience, but the neural basis for different spatial computations remain unknown. Medial entorhinal cortex layer II contains pyramidal island and stellate ocean cells. Here, we performed cell type-specific Ca 2+ imaging in freely exploring mice using cellular markers and a miniature head-mounted fluorescence microscope. We found that both oceans and islands contain grid cells in similar proportions, but island cell activity, including activity in a proportion of grid cells, is significantly more speed modulated than ocean cell activity. We speculate that this differential property reflects island cells' and ocean cells' contribution to different downstream functions: island cells may contribute more to spatial path integration, whereas ocean cells may facilitate contextual representation in downstream circuits.speed | grid cell | calcium imaging | entorhinal | hippocampus

Rhythms of the hippocampal network

“…The increased excitatory drive onto interneurons needed to produce fast gamma may be provided by increased spiking in MEC projection neurons. In support of this idea, both spiking activity in MEC neurons in rats and mice 142-144 and the power of fast gamma in rats 125,142,145 have been shown to increase with increased running speed. However, a different mechanism may promote slow gamma firing in gamma-generating interneurons.…”

Altered Oscillatory Dynamics of CA1 Parvalbumin Basket Cells during Theta–Gamma Rhythmopathies of Temporal Lobe Epilepsy

“…3 A ; Lasztóczi and Klausberger, 2014; Schomburg et al, 2014). Possibly, perforant path-associated interneurons may play a role in this dendritic mid-gamma oscillation, either in response to layer II island cells (Sun et al, 2015) or due to entorhinal cortex long-range inhibition (Basu et al, 2016). Feedback disinhibition of PV-positive interneurons, including bistratified and axo-axonic cells, appears also necessary for mid-gamma oscillations at the theta peak (Wulff et al, 2009).…”

Spatial representation in the hippocampal formation: a history

“…Including the entire entorhinal-hippocampal circuit A key objective for a more complete understanding of entorhinal-hippocampal function will be to determine how cell types with different functional correlates map onto the variety of morphological or neurochemical cell types and their unique connectivity patterns. Recent data suggest that, in layer II of MEC, both stellate and pyramidal cells can be grid cells, although stellate cells may comprise the majority of them 256,257,[272][273][274][275] . If so, are grid patterns created independently in these two cell classes, or does one of them inherit the grid from the other?…”