Episodic memory of experience of novel space is constructed by several sub-ensembles within a single engram population.
a. Diagrammatic representation of NMF analysis; colored bars indicate the relative activity of each neuron in the detected pattern (shown as the magnitude) (left), and the relative intensity of the synchronous activity of this pattern across time (right).
b. Example of two detected engram sub-ensembles. Distribution map of detected engram cells (left panel). Green and red magenta filled contours indicate neurons assigned to two different ensembles (corresponding to patterns #5 and #9, respectively), and yellow filled contours denote cells shared between patterns. Scale bar, 100 μm. The temporal pattern of synchronous activities of patterns #5 and #9 during experiencing novel space (top and middle right) and their overlay (bottom right).