The influence of DC-polarization of the endocochlear potential on single fibre activity in the pigeon cochlear nerve

Abstract

The endocochlear potential (EP) in the pigeon ear was altered by injecting current into the scala media. Simultaneous recordings from afferent fibres in the cochlear ganglion were performed. The mean rate of spontaneous activity was little affected by current injection and the consequent shifts in EP. In contrast to this lack of effect, the preferred intervals seen in some fibres in birds were accentuated by positive current injection and reduced or in some cases suppressed by negative current injection. The threshold of the tuning curve was raised by injection of negative current but the characteristic frequency showed little change. Sharpness of tuning decreased. Analysis of the results shows that current injection in the scala media produces significant changes in the filter characteristics of the cochlea, as well as altering the driving force for the transduction process (difference between EP and hair cell membrane potential).