Analysis of Summating Potential in Cochlear Responses of Guinea Pigs

Abstract

The polarity of the summating potential in the cochlear responses to short modulated bursts of tone (pips) varies with frequency. In scala vestibuli of the first cochlear turn the 8000 cps pip produces a summating potential that is negative relative to the neck and the 500 cps pip produces a positive one. There is no apparent summating potential in response to the 2000 cps pip. With death the polarity of the summating potential becomes positive for tone-pips of all frequencies and then later becomes negative for all pips. After damage to the cochlea the summating potential becomes strongly negative in scala vestibuli for all pips. When the guinea pig then dies there are no reversals in the polarity of the summating potential. Three components of the summating potential with varying resistance to lack of O2 and injury are postulated.