Description[edit]
As the basilar membrane vibrates, each clump of hair cells along its length is deflected in time with the sound components as filtered by basilar membrane tuning for its position. The more intense this vibration is, the more the hair cells are deflected and the more likely they are to cause cochlear nerve firings. Temporal theory supposes that the consistent timing patterns, whether at high or low average firing rate, code for a consistent pitch percept.
High amplitudes[edit]
At high sounds levels, nerve fibers whose characteristic frequencies do not exactly match the stimulus still respond, because of the motion induced in larger areas of the basilar membrane by loud sounds. Temporal theory can help explain how we maintain this discrimination. Even when a larger group of nerve fibers are all firing, there is a periodicity to this firing, which corresponds to the periodicity of the stimulus.
Experiments to distinguish rate and place effects on pitch perception[edit]
Experiments to distinguish between place theory and rate theory using subjects with normal hearing are easy to devise, because of the strong correlation between rate and place: large vibrations at a low rate are produced at the apical end of the basilar membrane while large vibrations at a high rate are produced at the basal end. The two stimulus parameters can, however, be controlled independently using cochlear implants: pulses with a range of rates can be applied via different pairs of electrodes distributed along the membrane and subjects can be asked to rate a stimulus on a pitch scale.
Experiments using implant recipients (who had previously had normal hearing) showed that, at stimulation rates below about 500 Hz, ratings on a pitch scale were proportional to the log of stimulation rate, but also decreased with distance from the round window. At higher rates, the effect of rate became weaker, but the effect of place was still strong.[6]