1. Neurosphere Migration

2. Delaloy et al., 2009 Method 1: Measuring distance of farthest neuron
Counting the number of neurons migrated
Figure 4

3. Delaloy et al., 2009
( In vitro Migration All migration experiments with rat cortical NPCs were performed in the presence of FGF2 and epidermal growth factor on plastic substrates. One day after transfection with Lipofectamine 2000, half of the medium was replaced with fresh medium. Culture dishes were handled carefully to keep the neurospheres at the bottom. Cell migration was evaluated by counting cells that had migrated out from the neurospheres and measuring the distance from the edge of the neurosphere to the nucleus of the most distant cell.
Delaloy, C., Liu, L., Lee, J.-A., Su, H., Shen, F., Yang, G.-Y., … Gao, F.-B. (2010). MicroRNA-9 Coordinates Proliferation and Migration of Human Embryonic Stem Cell-Derived Neural Progenitors. Cell Stem Cell, 6(4), 323–335.

4. Brennand et al., 2015
Method 3:
Calculate average distance from neurosphere to migrated neurons
Figure 3

5. Brennand et al., 2015
(Article)
(Supplementary Information) The protocol is in the supplementary: Neurosphere migration assay
NPCs were dissociated with accutase and then cultured for 72 hours in nonadherent plates to generate neurospheres.  Neurospheres were manually picked and cultured in a matrigel matrix (0.5 mg Matrigel was plated in NPC media on a 96-well plate 1 hour prior to neurosphere plating; following neurosphere picking, an additional 0.5 mg Matrigel was added in NPC media per 96-well plate). Neurospheres were manually centered in each well using a P200 pipet.  After 48 hours of migration, neurospheres were fixed in 4 paraformaldehyde in PBS at 4°C for 10 minutes, washed with PBS, stained with 0.5 μg/ml DAPI (4',6-diamidino-2-phenylindole) for 15 minutes and washed again in PBS. One 4x DAPI field of view was imaged per neurosphere; only images in which the neurosphere remained situated in the center of the well were analyzed. The average distance between the radius of the inner neurosphere (dense aggregate of nuclei) and outer circumference of cells (average migration) was measured using NIH ImageJ.  Note that high passage NPCs show inconsistent migration in vitro and should not be used in this assay.
Brennand, K., Savas, J. N., Kim, Y., Tran, N., Simone, a, Hashimoto-Torii, K., … Gage, F. H. (2014). Phenotypic differences in hiPSC NPCs derived from patients with schizophrenia. Molecular Psychiatry, 20(February), 1–8.

6. Bessa, Quehal, and Amaral, 2013
Used for neurite outgrowth, but potentially applicable to neuron migration
Calculate the ratio of outgrowth area to neurosphere area
Measure the maximum distance of outgrowth
Calculate the average distance of outgrowth
Notes:
Available as an ImageJ plugin?
Up to 27.71% average difference from manual measurements.
Bessa, S., Quelhas, P., & Amaral, I. (2013). Automatic Quantification of Cell Outgrowth from Neurospheres. In J. Sanches, L. Micó, & J. Cardoso (Eds.), Pattern Recognition and Image Analysis SE  - 16 (Vol. 7887, pp. 141–148). Springer Berlin Heidelberg.