Ontogenic changes in cochlear characteristic frequency at a basal turn location as reflected in the summating potential.

In these experiments the development of summating potential (SP) responses in gerbils from neonates to adults was followed. Special recording techniques were used to eliminate maturational effects associated with the middle ear so that developmental changes in cochlear physiology were isolated for study. Results indicate that as development proceeds the frequency that maximally excites the basilar membrane (BM) of the gerbil at a specific mid-basal turn electrode location progresses from low to high, demonstrating a 1.5 octave shift from the onset of the generation of electrical activity until adult-like response are obtained. These findings support the theory proposed by E.W. Rubel (in: Handbook of Sensory Physiology, Vol. IX: Development of Sensory Systems, pp. 135-237. Editor: M. Jacobsen. Springer-Verlag, New York) which explains the observed development of physiological responses measured in the cochlea and higher centers in terms of changing micromechanical transduction properties of the BM.