Comparing human electrocochleography responses to click and chirp stimuli

It is not known how electrocochleography components of action potentials (AP) and summating potentials (SP) are changed in response to CE-chirp stimulus using extra-tympanic electrodes. This study was done for comparing summating potentials and action potentials specifications in response to CE-chirp and click stimuli. Electrocochleography components of action potentials and summating potentials were recorded in 16 normal hearing subjects (8 men and 8 women) aged 22-30 years (mean: 26.7 with SD 2.5 years) with audiometric (250-8000 Hz) hearing thresholds of 15 dB HL or better in response to click and CE-chirp stimulus at 90 dB nHL. Amplitude, duration, latency and area of summating potentials and action potentials and SP/AP amplitude and area ratios were compared. Among the measured parameters, action potentials amplitude in response to CE-chirp stimulus (0.41 with SD 0.26 µV) was significantly smaller than action potentials amplitude in response to click (0.61 with SD 0.29 µV) stimulus (p<0.005). Relative frequency of detecting summating potentials in response to CE-chirp (68.7%) was lower than (100%) click (p<0.005). Recording electrocochleography component of summating potentials and action potentials with CE-chirp stimulus at high intensity level in normal hearing individuals shows no advantage over click stimulus. Small amplitude of summating potentials as a major problem of extra-tympanic electrocochleography cannot be solved using CE-chirp stimulus.