On the determination of input sound frequencies by the auditory central processor

The author discusses a flaw in an auditory central processor theory which states that the action potential (AP) output of neurons associated with hair cells is partially synchronized to the incoming f _in or its subharmonics. The main objection to this proposal is that synchronization seems to fail for high-frequency audio inputs. It is shown that this failure may be due to experimental difficulties. It is impossible to avoid trauma to the cochlea and/or auditory nerve. To study synchronization at 10,000 Hz, the interspike-interval (LSI) histogram requires a timing accuracy of 4 mu s or better despite input APs that have a risetime of 200 mu s. Synthetic AP interspike-interval histograms are derived for unstimulated, fully synchronized, low-frequency, and high-frequency audio input conditions. The latter are compared with typical experimentally derived data. Hypothetical processing by reverberatory neurons is considered.