Deep entorhinal cortex: from circuit organization to spatial cognition and memory

The circuit organization of the deep layers of the entorhinal cortex suggests multi-stage processing of hippocampal, cortical, and superficial entorhinal inputs. Neurons in layer 5a (L5a) provide the main output from deep layers of the entorhinal cortex to the telencephalon, whereas neurons in L5b influence superficial entorhinal cortex. Hippocampal replay events and cortical up–down states preferentially engage neurons in L5b of entorhinal cortex. The deep layers of the entorhinal cortex are crucial for memory storage, consolidation, and retrieval, and neurons in L5a and 5b probably play different roles. Accounting for multistage processing by the deep entorhinal cortex may be important for establishing systems-level mechanisms of episodic memory and spatial cognition. The deep layers of the entorhinal cortex are important for spatial cognition, as well as memory storage, consolidation and retrieval. A long-standing hypothesis is that deep-layer neurons relay spatial and memory-related signals between the hippocampus and telencephalon. We review the implications of recent circuit-level analyses that suggest more complex roles. The organization of deep entorhinal layers is consistent with multi-stage processing by specialized cell populations; in this framework, hippocampal, neocortical, and subcortical inputs are integrated to generate representations for use by targets in the telencephalon and for feedback to the superficial entorhinal cortex and hippocampus. Addressing individual sublayers of the deep entorhinal cortex in future experiments and models will be important for establishing systems-level mechanisms for spatial cognition and episodic memory. The deep layers of the entorhinal cortex are important for spatial cognition, as well as memory storage, consolidation and retrieval. A long-standing hypothesis is that deep-layer neurons relay spatial and memory-related signals between the hippocampus and telencephalon. We review the implications of recent circuit-level analyses that suggest more complex roles. The organization of deep entorhinal layers is consistent with multi-stage processing by specialized cell populations; in this framework, hippocampal, neocortical, and subcortical inputs are integrated to generate representations for use by targets in the telencephalon and for feedback to the superficial entorhinal cortex and hippocampus. Addressing individual sublayers of the deep entorhinal cortex in future experiments and models will be important for establishing systems-level mechanisms for spatial cognition and episodic memory. dendrites originating from the apex (pointed part) of the soma of a pyramidal cell. In the entorhinal cortex, these dendrites usually project towards the surface of the brain. dendrites originating from the base of the soma of a pyramidal cell. the structural arrangement of neurons. the area around a local maximum in the firing-rate map of cells such as place cells and grid cells. a neuron that represents location through multiple discrete firing fields that have a grid-like arrangement in which fields correspond to the apices of a series of tessellating triangles. estimating position relative to a known starting point using self-motion signals. a type of excitatory neuron with a 'pyramid'-shaped soma, a relatively wide and long apical dendrite, and multiple basal dendrites. a deflection in the field potential with superimposed high-frequency oscillations. These are usually observed during sleep and resting states. excitatory neurons whose dendrites are oriented in a star-like shape and that are found in layer 2 of the entorhinal cortex. a protein that controls the transcription of a gene.