The Temporal Relationship between Basilar Membrane Motion and Nerve Impulse Initiation in Auditory Nerve Fibers of Guinea Pigs

Abstract

When the helicotrema was obstructed in guinea pigs, trapezoidal displacement of the round window membrane produced a trapezoidal microphonic which indicated a unidirectional displacement of the entire length of the basilar membrane. Responses of single auditory nerve fibers to the trapezoidal displacement of the round window membrane were recorded after obstruction of the helicotrema. About 39 % of the 424 fibers showed tonic responses which demonstrated directional sensitivity. More than 90 % of these fibers increased their discharge rate during displacement of the basilar membrane toward the scala tympani and decreased their discharge rate during oppositely directed displacement. Less than 5 % of the tonic fibers responded in the reverse manner. About 23 % of the auditory nerve fibers responded to onset and/or cessation of trapezoidal motion of the basilar membrane. About 28 showed a combination of the tonic and phasic responses. However it is probably that all phasic responses we observed do not arise from velocitysensitive fibers but some may represent artifacts. Both possibilities remain open until further studies are performed. The transduction mechanism of the cochlea is discussed on the basis of our data obtained by unidirectional displacement of the basilar membrane.

Modulation of activity in starling cochlear ganglion units by middle-ear muscle contractions, perilymph movements and lagena stimuli

“…This finding contradicts the proposal of Schwartzkopff and Necker mentioned above. However, it is in agreement with the results of Konishi and Nielsen (1978) in guinea pigs and of Crawford and Fettiplace (1983) in tur-tles who found an excitation of primary auditory units to a displacement of the basilar membrane towards scala tympani.…”

Acoustic stimulation causes tonotopic alterations in the length of isolated outer hair cells from guinea pig hearing organ.

“…The existence of biasing in the position of the basilar membrane during high-frequency tones has been demonstrated in the intact organ of Corti, implying that the length changes reported here for solitary hair cells may have an "in vivo" correlate (10). It remains to be seen whether the acoustically induced tonotopic alterations in the length of outer hair cells reported here relate to a number of intriguing observations concerning frequency-specific phase transitions of basilar membrane motion and the excitation of cochlear afferent nerve fibers (10)(11)(12)(13).…”

Chinchilla auditory-nerve responses to low-frequency tones

“…This figure includes data on auditory-nerve fibers of chinchilla (responses to tones, this study and Ingvarsson, 1981 ), cat (responses to 50-Hz tones, Pfeiffer and Kim, 1975), and mongolian gerbil (responses to trapezoids, Sokolich et al, 1976;Zwislocki and Sokolich, 1974;Zwislocki, 1977;Schmiedt et al, 1980). All other data pertain to guinea pigs: auditory-nerve fibers (responses to 100-Hz tones, Maceri et al, 1982, and responses to trapezoids, Konishi and Nielsen, 1978), basal ganglion neurons (responses to tones, Sellick et al, 1981Sellick et al, , 1982, basal inner hair cells (Sellick and Russell, 1980), and basal outer hair cells (Tanakp et al, 1980). In constructing this figure we have generally plotted responses according to the investigators' own interpretation of their data.…”