ACCURATE BINAURAL MIRRORING OF SPONTANEOUS OTOACOUSTIC EMISSIONS SUGGESTS INFLUENCE OF TIME-LOCKING IN MEDIAL EFFERENTS

Spontaneous otoacoustic emissions (SOAEs) of nearly identical acoustic frequency in both ears are a common observation, but it is unknown if this binaural mirroring effect is random, artefactual, genetic, devel opmental, or of other origin. The available raw datal of all human SOA E surveys were pooled, and the intervals of all possible binaural emis sion pairs (N = 9555) were listed according to size on the Cent-scale (I Cent = 1/100 semitone = 1/1200 octave). Statistical analysis showed (1) a slight broad-band mirroring in the 0-100 Cent range (P < 0.05), and (2) a strong narrow-band mirroring (NBM) in the 0-20 Cent range ( P < 0.001). Negative results in a detailed SOAE cluster detection prog ram excluded experimental artefacts as causes of NBM. Analysis of the large subgroup of twin data excluded genetic and intrauterine developm ental causes. Systemic developmental causes are unrealistic, as 20 Cen t corresponds to only similar to 80 mu m on the cochlear map. Analysis of infant data indicated that the effect may be introduced after birt h by secondary factors. Interaural crosstalk was examined but had to b e rejected. It is suggested that bilaterally spreading period informat ion in the medial olivocochlear system influences outer hair cells of the same best frequency in both ears very similarly. Evidence concerni ng possible effects on electromotility is discussed, and experimental tests are proposed. (C) 1998 Elsevier Science B.V.