Figure 6.

A–D, Deletion of either M₂ or M₄ mAChRs or both elevated high-frequency DPOAE (A) and ABR (B) thresholds and reduced suprathreshold neural responses (D) even in midcochlear regions in which thresholds (A, B) and DPOAEs (C) were normal. A, B, Mean DPOAE or ABR thresholds for groups of 6–8 week mutants and wild-type controls (numbers in each group are given in Table 2). C, D, Mean amplitude-versus-level functions for the same animals from A and B, as seen in DPOAEs or ABRs evoked by tones at 16 kHz (for DPOAEs, f₂ = 16 kHz). For ABRs, only wave 1, the earliest negative–positive deflection, was measured. Error bars in all panels represent SEMs: the symbol key in A applies to all panels.