Cochlear electrical activity in the C57BL/6 laboratory mouse: volume-conducted vertex and round window responses

Remote (vertex-positive, volume-conducted) and local (round window, or RW) responses were simultaneously recorded from the C57BL/6 mouse. Volume-conducted responses were obtained which corresponded to the cochlear microphonic (CM), summating potential (SP), and action potential (AP), as measured at the RW. The vertex PI, corresponding to the AP, had a shorter latency to rarefaction than to condensation clicks. At higher SPL's bimodal PI peaks (a and b) were observed. PIb amplitudes were greater at lower, and PIa amplitudes were greater at higher SPL'S. Responses subsequent to the RW N1 and the volume-conducted P1 were eliminated after the ear was isolated from the brainstem.