Fig. 11. (A) A compound action potential response, measured from the round window of the cochlea. Foxi1^+/+ and Foxi1^+/- littermates showed thresholds (±s.e.m.) that were very similar to each other, but relatively high compared with other mouse strains especially at high frequencies, suggesting that the genetic background of these mice (mostly CD-1) was associated with poor hearing. Foxi1^-/- mice showed no cochlear responses of any sort, up to maximum sound output used; indicated by the black triangles at the top of the graph (n=7, Foxi1^+/+; n=9, Foxi1^+/-; n=10, Foxi1^-/-). (B) Mean endocochlear potentials (EP; ±s.e.m.) from wild type, heterozygote and null mutant littermates aged 29 to 129 days. There was no difference in the EPs in wild types and heterozygotes, but homozygous mutants showed potentials close to zero (n=14, Foxi1^+/+; n=18, Foxi1^+/-; n=19, Foxi1^-/-).