Temporal theory

The temporal theory of hearing states that human perception of sound depends on temporal patterns with which neurons respond to sound in the cochlea. Therefore, in this theory, the pitch of a pure tone is determined by the period of neuron firing patterns—either of single neurons, or groups as described by the volley theory. Temporal or timing theory competes with the place theory of hearing, which instead states that pitch is signaled according to the locations of vibrations along the basilar membrane.

Temporal theory was first suggested by August Seebeck.

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.

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.

Neurons have a maximum firing frequency within the range of frequencies we can hear. To be complete, rate theory must somehow explain how we distinguish pitches above this maximum firing rate. The volley theory, in which groups of neurons cooperate to code the temporal pattern, is an attempt to make the temporal theory more complete, but some frequencies are too high to see any synchrony in the cochlear nerve firings.

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