A new low-noise signal acquisition protocol and electrode placement for electrocochleography (ECOG) recordings

Electrocochleography (ECOG) is a low-amplitude electrophysiological measurement technique primarily used as an assistive tool for the diagnosis of Ménière's disease. Of the two types of ECOG, transtympanic (TT) and extratympanic (ET), ET-ECOG has gained popularity due to its noninvasive nature; however, it suffers from increased susceptibility to various types of noise, due to the low-signal amplitude (~1 µV scale) associated with the method. Therefore, reliably obtaining ECOG recordings involves an environment that minimally interferes with the recording, a low-noise signal recorder, and a carefully executed recording protocol. We propose a new method that involves a modified ear electrode and electrode placement protocol that offers a solution to reducing noise in ET-ECOG. Noise suppression is achieved by minimizing background biological noise, and thermal noise from electrode impedances, which were identified to be the main contributors to signal degradation in ET-ECOG. Results show that the proposed method yields a >2.6 dB improvement in SNR in comparison with the conventional method (p < 0.05); thus, a SNR obtained with ~880 repetitions using conventional method can be achieved with ~360 repetitions. Improved SNR demonstrate that the proposed method is capable of achieving faster recordings, while maintaining similar or better SNR compared to conventional methods.