Fig S1.

Pre-processing of the histological images. Top row: Based on an empirically defined RGB-threshold, cell-nuclei were removed from both the myelin images and the astrocyte images (the latter not shown here). Middle row: The colour-channel with the strongest staining intensity was selected for further processing, the red-channel in our case. Bottom row: To enhance astrocyte processes, the images were transformed to HSV-colourspace. The saturation-channel of the HSV images appeared to have contribution from primarily astrocyte staining and was used for further processing..