Comparison of electrically and acoustically evoked responses in the auditory cortex of the guinea pig: implications for a cochlear prosthesis.

Guinea pigs have been used to develop an animal model for evaluation of electric stimulation of the cochlea. Techniques were developed for recording from single neural units in the auditory cortex. Acoustic responses exhibit similar patterns of neural discharge ("on", "off", sustained excitation and inhibition, etc) to those reported for auditory neurons in other species. Similar response patterns are obtained when electric stimulation is used. However, cortical units display characteristic frequency tuning with acoustic stimulation, whereas it becomes increasingly difficult to evoke electric responses as stimulus frequency increases. Recording of gross evoked responses from the same cortical area indicates that the intensity function for electric stimulation is much steeper than that seen for acoustic stimulation.