| Summary: | Place cells are pyramidal neurons in CA1 and CA3 regions of hippocampus which fire selectively when the animal is located in a particular place in space. CA1 place cells receive synaptic input from CA3 via the Schaffer collateral fibers to their proximal apical and basal dendrites and from the third layer of medial entorhinal cortex to their apical tuft dendrites. Both of these input pathways encode spatial information. Grid cells, which form the entorhinal input to CA1 cells, have a spatial firing field with multiple peaks which displays a regularly spaced, triangular grid pattern that covers the entire space of a given environment. Both grid and place cells are phase-modulated by theta rhythm and this modulation may be important for their spatial properties.
Studying the formation of place cells is an important step in understanding how representation of the external environment is coded in neural networks that constitute spatial maps. It is not currently known how place fields emerge in CA1 neurons. An influential model of place cell formation predicts the convergence of various grid field inputs which combine linearly to create the place field output of CA1 cells.
In this study, we constructed a model of CA1 place cell formation through the convergence of grid field inputs to the distal dendrites of our model neuron. We created a model of grid cell activity which represents the firing of grid cells modulated be the theta rhythm. We varied the number of different grid fields used as synaptic inputs to stimulate the distal dendrites of a biophysically constrained, detailed compartmental CA1 pyramidal cell model. In addition, inhibition was placed in both the distal and proximal dendrites. These inhibitory pathways are known to be active in different phases of the theta rhythm. We used this model to study the properties of CA1 place cell formation and to assess the output of the CA1 model cell during place cell activity. Additionally, we examined the effects of local dendritic integration by altering the dendritic distribution of grid cell inputs. Finally, we examined the effect of theta modulation on the spatial extent, the coherence and the information content of CA1 place cells.
|
|---|
