I'm reading the article "A Topological Paradigm for Hippocampal Spatial Map Formation Using Persistent Homology" by Y. Dabaghian, F. Mémoli, L. Frank, G. Carlsson
I try to understand the following graph:
In part a) of the graph, we are seeing a bunch of colored points. These points are in the hippocampus of the rat as opposed to the idea that these points are in the plane on which the rat is moving, and so each point is a place cell of the hippocampus that has fired at some moment in some place of the plane on which the rat is moving. Normally there is a huge number of points in this picture but we chose to put only those who fired, those who did not fire are deleted from the picture of part a). Also, each point (which means each place cell) has one color, and two place cells having the same color designate that the two place cells are considered identical and will be treated as a single place cell in the part b) of the figure.
In part b), we record the time at which each point has fired, with each point being represented by a bar on the time axis and all the bars are identical (same height, and same thickness).
In part c) the picture is in the plane on which the rat is moving as opposed to the idea that the picture of part c) is in the hippocampus of the rat. In part c) we are trying to derive the place fields from part b). Deriving the place fields means here that we are deriving the path that the rat has taken. In particular, place fields are in the plane on which the rat is moving and not in the hippocampus, and each place field in the plane is determined by seeing which place cells in the hippocampus has fired at that area of the plane.
Is my understanding correct? I'm not a specialist but I need to understand each detail of this graph because my work depends on it. My confusion comes from the fact that there are two regions here: the hippocampus of the rat and the plane on which the rat is moving and I need to be sure in which region the picture is.