Across-species comparisons of psychophysical detection thresholds for electrical stimulation of the cochlea: II. Strength-duration functions for single, biphasic pulses.

This paper compares psychophysical detection threshold data (new and previously published) for pulsatile electrical stimulation of the deafened inner ear, obtained from different human and nonhuman subjects. Subjects were grouped according to species. Other variables, however, such as the electrode array type and method of deafening, varied within and across species. Detection threshold levels and slopes of threshold versus phase duration functions for presentations of single, biphasic pulsatile stimuli (strength-duration functions) were compared for humans, macaques, cats, and guinea pigs. For bipolar stimulation, statistically significant differences in threshold level were observed between human subjects and all other species. The species difference did not depend on the phase duration tested. For monopolar stimulation, only nonhuman species were tested. Effects of electrode configuration on both the level and slope of psychophysical strength-duration functions were statistically significant across nonhuman species, but there was not a statistically significant interaction between species and electrode configuration. The similarity in function shape and relative paucity of significant differences in psychophysical functions across species support the continued use of multiple species for cochlear implant research.