Comment on "Auditory-nerve first-spike latency and auditory absolute threshold: a computer model" [J. Acoust. Soc....

A recent paper by Meddis [J. Acoust. Soc. Am. 119, 406-417 (2006)] shows that an existing model of the auditory nerve [Meddis and O'Mard, J. Acoust. Soc. Am. 117, 3787-3798 (2005)] is consistent with experimentally-measured first-spike latencies in the auditory nerve [Heil and Neubauer, J. Neurosci. 21, 7404-7415 (2001)]. The paper states that this consistency emerges because in the model, the calcium concentration inside the inner hair cell builds up over long periods of time (up to at least 200 ms) during tone presentation. It further states that integration over long time-scales happens despite the very short time constants (< 1 ms) used for the calcium dynamics. This letter demonstrates that these statements are incorrect. It is shown by simulation that calcium concentration inside the hair cell stage of the Meddis model rapidly reaches a steady state within a few milliseconds of a stimulus onset, exactly as expected from the short time-constant in the simple first-order differential equation used to model the calcium concentration. The success of the Meddis model in fitting experimental data actually confirms earlier results [Krishna, J. Comput. Neurosci. 13, 71-91 (2002a)] that show that the experimental data are a natural result of stochasticity in the synaptic events leading up to spike-generation in the auditory nerve; integration over long time scales is not necessary to model the experimental data.