The effects of stochastic neural activity in a model predicting intensity perception with cochlear implants: Low-rate stimulation

Most models of auditory nerve response to electrical stimulation are determ inistic, despite significant physiological evidence for stochastic activity . Furthermore, psychophysical models and analyses of physiological data usi ng deterministic descriptions do not accurately predict many psychophysical phenomena. In this paper we investigate whether inclusion of stochastic ac tivity in neural models improves such predictions. To avoid the complicatio n of interpulse interactions and to enable the use of a simpler and faster auditory nerve model me restrict our investigation to single pulses and tow -rate(<200 pulses/s) pulse trains. We apply signal detection theory to prod uce direct predictions of behavioral threshold, dynamic range and intensity difference limen, Specifically, we investigate threshold versus pulse dura tion (the strength-duration characteristics), threshold and uncomfortable l oudness (and the corresponding dynamic range) versus phase duration, the ef fects of electrode configuration on dynamic range and on strength-duration, threshold versus number of pulses (the temporal-integration characteristic s), intensity difference limen as a function of loudness, and the effects o f neural survival on these measures. For all psychophysical measures invest igated, the inclusion of stochastic activity in the auditory nerve model wa s found to produce more accurate predictions.