Dendritic, Cellular and Circuit Mechanisms of Spatial Representations

Abstract

How are neuronal representations of the spatial environment generated at the level of synapses, neurons, and neuronal circuits? Neurons in the hippocampal formation produce striking spatial firing patterns that may provide the brain with a cognitive map of the environment. We have combined computational modelling, in vivo and in vitro recordings to understand how spatially modulated firing is generated at the synaptic, cellular and network level. We address this question in several key circuits that are critical for spatial cognition and memory, such as the medial entorhinal cortex and the dentate gyrus. We find that in both regions, nonlinear properties of individual neurons can specifically contribute to the computations performed by these circuits: In the medial entorhinal cortex, nonlinear integration can sharpen the precision of the temporal code and enhance the robustness of the rate code of grid cell firing, whereas in the dentate gyrus, nonlinear properties of individual neurons can help to distinguish between similar synaptic inputs patterns.