Notably, differentiated cells transferred to growth factor conditions exhibited similar velocity and tortuosity compared to differentiated cells maintained in FBS conditions at all times. Interestingly, methylation level specific kind although differentiated cells consistently displayed low displacement in the direction of the dcEF and low directedness of migration, differentiated cells transferred to growth factor conditions showed a tendency to increased displacement towards the cathode relative to differentiated cells maintained in FBS at all times. Taken together, this suggests that the lack of rapid and cathodally-directed migration in differentiated cells is not due to the lack of EGF and bFGF signaling in the cells, and that growth factor signaling may impact the direction, but not the velocity, of these cells�� migration. Figure 5 summarizes and compares the migratory behaviour of both differentiated and undifferentiated cells in either the absence or presence of a dcEF using 2-way Anova analysis. The conductivity of the culture media is imparted by its electrolyte constituents. As such, the existence of charged molecules within the media render the possibility of an electric field-induced redistribution of the electrolytes to form a chemotactic gradient. We asked whether the observed directed migration of the NPCs was a direct effect of the dcEF, or if the cells were responding to a dcEF-induced chemical gradient. To eliminate the possibility of a chemical gradient forming within the galvanotaxis chamber, we designed a novel chamber that permitted the continuous perfusion of fresh SFM+EGF, bFGF, and heparin. The dcEF was maintained in the direction of the positive X-axis as in previous experiments, while media was continuously perfused in the direction of the negative X-axis, opposing the electric current flow. We demonstrated that the lack of migration of differentiated cells was not due to the lack of EGF since the addition of EGF could not rescue the galvanotactic response of differentiated cells. Next we asked if EGF signaling was important for the migratory behaviour of undifferentiated SE NPCs as previously described for other cell types. We plated undifferentiated neurospheres into galvanotaxis chambers as before for 17 hours. Following this, the media was aspirated from the chambers, the troughs were gently washed and fresh SFM supplemented only with bFGF and heparin was immediately applied into the chamber and media reservoirs. The bFGF was present in order to maintain the NPCs in an undifferentiated state. Time-lapse imaging revealed that in the absence of EGF, NPCs exhibited significantly reduced dcEF-axis displacement, velocity, and directedness of migration, as well as significantly increased tortuosity compared to NPCs maintained in the presence of EGF at all times. We further demonstrated a role for EGF signaling in NPC galvanotaxis using the EGFR blocker, erlotinib which inhibits EGFR tyrosine kinase activity by preventing EGFR autophosphorylation via competitive binding to the ATP binding domain. NPCs cultured in the presence of growth factors, with erlotinib migrated at a significantly decreased velocity, and increased tortuosity relative to vehicle controls and NPCs in growth factor conditions alone. Immunostaining verified that the NPCs remained nestin-positive after 2.5 hours of dcEF exposure in the presence of erlotinib, suggesting that FGF2 is sufficient to maintain cells in an undifferentiated state within this time period.