Effectiveness of middle ear electrical stimulation for activating central auditory pathways.

Electrical stimulation of afferent auditory elements through electrodes placed in the middle ear was investigated in acute guinea pig preparations. Thresholds for auditory activation were current dependent for low frequencies (less than 1 kHz) and charge-dependent at higher frequencies. Threshold currents were 3-5 times those for intracochlear stimulation. Mechanisms of activation were examined with removal of cochlear fluids and injection of neomycin, Xylocaine, saline, and artificial perilymph with different calcium concentrations. Neurons of the spiral ganglion are indicated as mediators of this stimulation.