Temporal non-linearities of the cochlear amplifier revealed by maximum length sequence stimulation.
OBJECTIVE
The objective of this study was to examine whether temporal non-linearities of the cochlear amplifier, as reflected by otoacoustic emissions (OAEs), exist and are distinct from any recording system non-linearities.


METHODS
Maximum length sequence stimulation, at various stimulus rates, was used to evoke OAEs from normally hearing subjects. Recordings from a 2cc cavity were also made. The data were analyzed to obtain the linear response and estimates of the slices of the 2nd and 3rd order Volterra kernels. This provided a measure of two and 3 click non-linear temporal interactions, respectively.


RESULTS
The results showed that temporal non-linearities of OAEs do exist, are stable and repeatable within individuals and have properties that differ from those shown by the conventional linear response. Whilst some of the non-linear response properties conformed to the expected pattern, of increasing amplitude with increase in stimulus rate, there are some areas in which they show an unpredicted complexity.


CONCLUSIONS
Whilst system non-linearities could be found, there was no difficulty in distinguishing between the physiological and system non-linear components. New areas of research and application may result from the use of these new OAE responses.
Thornton
A R
AR
MRC Institute of Hearing Research, Royal South Hants Hospital, Brinton's Terrace, SO14 0YG, Southampton, UK. ardt@soton.ac.uk
Shin
K
K
Gottesman
E
E
Hine
J
J
D000161:Acoustic Stimulation; D000328:Adult; D002138:Calibration; D003051:Cochlea / Q000502:physiology*; D006801:Humans; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D011930:Reaction Time; D012016:Reference Values