Fig. 1

Single-axon-resolution imaging of axon degeneration in the living brain. a Timeline of imaging and injury to study cortical axon degeneration in vivo. b A region of axon ready for lesioning (left); a binary mask (4 μm) is placed over the axon (green circle) and a focused laser beam used to induce axotomy, verified by imaging immediately after lesion (right). Proximal is up and distal is down. c Representative drawings of axon segments before lesioning used throughout the study. Black filled circles indicate terminal axon endings. d A representative axon before lesioning, total length 1289 μm. e Representative drawings of the disconnected portion of the axon in the dotted box in d illustrating axonal degeneration over selected time points. Time in hours post-lesion and percentage of axon remaining are indicated. f Representative example of quantification of the degeneration onset (23 h) and g calculation of fragmentation rate for the axon in d, e (1.45 μm/min). Scale bar = 5 μm (b), 150 μm (c), 200 μm (d) and 300 μm (e)