182602.fig.004a
(a)
182602.fig.004b
(b)
Figure 4: The contextual gating model of place field generation. (a) Place cells receive inputs from grid cells of varying scales (shown by the small versus large circles in the units). The connections are intercepted by convergent contextual inputs which facilitate (or perhaps inhibit) the grid cell inputs and thus determine which grid cells actually drive the place field. In this way, constant activity from the grid cells is converted into context-specific activity in the place cells. When the context is changed, the matrix of activated synaptic connections alters—if this is sufficiently large then a new pattern of grid cells will drive the place cell to fire differently (completely remap); if it is small, the cell will still fire in the same place, but perhaps with a different rate (rate remap). (b) A schematic of the context gating model at the single-cell level, showing how the contextual inputs in the distal dendrites terminate on the same branch of the dendritic tree as some of the spatial (grid cell) inputs. In the black box (left), the context inputs signalling that the box is black interact synergistically with a subset of the spatial inputs, producing the field seen in the black box below; when the box is white (right), a different branch of the dendrite is depolarised and a different set of spatial inputs facilitated.