Animals

All mouse experiments were performed according to the guidelines of the national law (Tierschutzgesetz der Bundesrepublik Deutschland, TierSchG) regarding animal protection procedures and approved by the responsible authorities, the Niedersächsisches Landesamt für Verbraucherschutz und Lebensmittelsicherheit (LAVES, AZ 33.19-42502-04-17/2479) and Regierung von Oberbayern (AZ 55.2-1-54-2532-11-2016). Thy1-GFP (M-line, hereafter called CTR) (26) and crosses of SOD1^G93A (32) and GFP-M mice (referred to as SOD) were used in groups of up to five mice per cage, with ad libitum access to food and water. Mice were kept at a 12/12-hour light/dark cycle. Mice were implanted at the age of 19 to 23 weeks, and imaging commenced at 23 to 27 weeks of age. In total, 7 males and 4 females, 5 CTR (2 males and 3 females), 6 SOD (5 males and 1 female), were used, out of which 10 of the 11 mice were imaged eight times, and 1 mouse was imaged only five times. However, not all field of views could be imaged during each session due to the appearance of motion artifacts linked to blood vessel pulsation. The maximum number of consecutive imaging TPs per field of view assessed per mouse was as follows: two TP (one mouse), four TP (three mice), six TP (one mouse), seven TP (one mouse), and eight TP (five mice).