Fig. 2.

The top and bottom of the OHC region move most out of phase at low frequencies and low stimulus levels. (A) Phase differences between the RL and OHC-DC from spatial maps of responses to 4- to 9-kHz tones presented at 60- or 70-dB SPL. Roughly out-of-phase motion (indicated by shaded area; 0.5 cycles = truly antiphasic) was observed up to ∼20 kHz. Individual/average phase differences (open/closed symbols) at f and its harmonics are plotted versus the response frequency. Averages are shown when data were available from at least three mice. When responses at both 60- and 70-dB SPL were obtained in individual mice, phase differences were first averaged across levels prior to plotting and inclusion in the group average. (B and C) Average phase differences between the RL and OHC-DC (at f) for 70-dB SPL tones swept in frequency (B) or 9-kHz tones swept in level (C), demonstrating antiphasic motion at low frequencies and low SPLs. Data in B and C were derived from measurements from isolated points near the RL and OHC-DC rather than detailed spatial maps, which could only be obtained at a few stimulus frequencies and levels in each mouse.