English: Geometric transformation of VSDI data in the stratum radiatum. (A) The original 3D VSDI dataset, in pseudocolor. Warmer colors represent depolarization and cooler colors represent hyperpolarization. Black lines indicate the polygonal geometry used for geometric transformation. Anatomical transitions between the hilus and CA3, and between CA3 and CA1, are indicated with white lines. (B) For each video frame, and for each polygonal segment, the fluorescence values are averaged to obtain a single fluorescence value for that segment at that time point. These average ΔF/F fluorescence values are rendered in pseudocolor for each polygonal segment. (C) The raster plot is assembled by appending one column of averaged fluorescence values to the raster plot for each movie frame. For each movie frame, the pseudocolor values shown in the polygonal segments of panel B correspond exactly to the values in the rightmost column of the raster plot. This video shows the same recording that is shown in Figure 1.