A comparison of compound action potential and cochlear microphonic two-tone suppression in the guinea pig

Cochlear microphonics (CM) and compound action potentials (AP) were recorded simultaneously with differential electrodes in the basal turn of the guinea pig cochlea. When CM two-tone suppression (2TS) curves were compared to AP simultaneous masking curves, good correspondence was observed between CM and AP suppression effects. The relationship between the 10 dB bandwidths of CM and AP 2TS curves remained constant for each animal despite differences between animals resulting from natural variations. Under pathological conditions (acute cochlear hypoxia) both CM and AP two-tone suppression effects were greatly reduced or disappeared. These results can be taken as evidence that CM suppression and AP suppression are the products of a common underlying mechanism.