Table 1. Definition of the measures of regeneration.

Regeneration factor	Regeneration factors were measured as below when a neuron was categorized as regeneration
Retraction distance	The length of axon that was lost between the location of axotomy and the initial retraction bulb
Retraction bulb formation time	The time it took to form the initial retraction bulb, measured from the time point of axotomy
Regeneration ratio	The number of neurons that regenerated, over the total neurons which formed a retraction bulb
Regeneration initiation time	The time between the retraction bulb formation and the start of a steady extension lasting more than 1 hr and leading to regeneration
Regeneration length	The length of axon that extended within 2 hr after regeneration initiation time
Growth cone area	The average of the extending tip area measured at 20, 40, and 60 min after regeneration initiation