BDNF and deafness: Since the numbers of hair cells and SCs between treated and untreated cochleas did not differ in both BDNF-GS and BDNF-OP studies, the data were merged in order to analyze the effect of duration of deafness for each cell type of the organ of Corti (from six to fourteen weeks after deafening, that are the BDNF-GS and BDNF-OP studies respectively) (Figure 9).