Heurrng Resrarc~h. 12 (1983) 89-119 Elsevier HRR 00426 Some electrical circuit properties of the organ of Corti. I. Analysis without reactive elements Peter Dallos Auditorr Physmlogv L.ahoratoy (Audrology) and Department OJNrurobmlogv and Ph,rsiologr. North\ce.urrn Unu_xv~~f~, Euunston, IL 60201, U.S.A. (Received 3 January 1983; accepted 12 July 1983) A simplified network model of the organ of Corti is analyzed with the assumption of parametric excitation via resistance changes in the hair cells’ apical membrane. Pertinent network variables (intracell- ular resting and receptor potentials, cellular input resistance, extracellular potentials) depend on the ratios of basal (perilymphatic face) and apical (endolymphatic face) receptor cell resistances. denoted as shape factors. In the Appendix two methods are suggested for the computation of shape factors; both are based on the geometrical properties of hair cells. Various electrical quantities computed on the basis of shape factors are consistent with recent recordings from third turn inner and outer hair cells (Dallas et al. (1982): Science 218, 582-584). The model provides a plausible explanation for the experimentally observed discrepancy between inner and outer hair cell resting and receptor potentials. One potentially significant result of the analysis is the demonstration that since shape factors for outer hair cells are probably longitudinally graded, so must be all cellular electrical characteristics. Another interesting finding is that electrical interaction among neighboring hair cells is unlikely. A large-signal analysis of the circuit demonstrates that even in the absence of a non-linear input, the parametrically excited circuit itself generates pronounced distortion. The most significant consequence of this nonlinearity is a response asymmetry in which the depolarizing phase is greater than the hyperpolarizing one. Thus the circuit nonlinearity may. at least in part, account for the large positive d.c. response seen in both types of receptor cell (Dallos et al. (1982): Science 218. 582-584; Russell and Sellick (1978): J. Physiol. Lond. 284, 261-290). Key words: cochlear model; cochlear hair cell; sensory receptor; receptor potential Introduction Recent studies exploring the mammalian hearing organ with microelectrodes, including the recording of electrical activity from hair cells, have paved the way to a more quantitative description of the electrical environment in the organ of Corti [17,23,40,67,72]. A knowledge of cochlear electroanatomy is essential for the correct interpretation of measured sound-induced responses [10,20,59,89]. Probably more fundamentally, it is instrumental in evaluating schemes of electrical interactions and electrical communication within the organ of Corti which have been suggested in the past [35,44,45,64]. The term cochlear electroanatomy was introduced by von BCkttsy [3] to denote 0378-5955/83/$03.00 Q 1983 Elsevier Science Publishers B.V.