Two-tone suppression in auditory nerve of the cat: Rate-intensity and temporal analyses

Abstract

Responses to two-tone stimuli were recorded from auditory-nerve fibers in anesthetized cats. One tone, the suppressor, was set at a frequency above characteristic frequency and was fixed in intensity. A second tone was set at an excitatory frequency and was varied in intensity. The suppressor tone, when set at a sufficient level, always reduced the response to the excitatory tone by an amount equivalent to a fixed number of decibels, regardless of the excitatory tone's intensity. Estimates of suppression magnitude were derived from shifts in rate-intensity function obtained when the suppressor tone was present relative to the functions obtained for the excitatory tone alone. When suppressor-tone intensity was increased, suppression magnitude likewise increased. When the two tones were increasingly separated in frequency, either by varying the excitor or by varying the suppressor, suppression magnitude decreased monotonically. Suppression behaved in the same manner regardless of whether suppresor tone was excitatory or nonexcitatory. When frequency separation was small enough and when both tones were above the neuron's characteristic frequency, responses synchronized to low-order combination tones could be elicited. These responses usually possessed different rate-intensity characteristics and resulted in estimates of suppression magnitude which were spuriously low. When frequency separation is normalized with regard to position of traveling wave maxima within the cochlear duct, the magnitude of two-tone suppression for a given suppressor-tone intensity is seen to be frequency independent.

Neural representation of spectral and temporal information in speech

“…The assumption that such filters are an accurate model for AN fibres is only partly true, in that there are nonlinear effects that complicate cochlear tuning. Most important are the nonlinear interactions, which allow energy at one frequency to suppress responses to a different frequency (Sachs 1969;Javel et al 1978;Javel 1981;Delgutte 1990).…”

Development of single- and two-tone responses of anteroventral cochlear nucleus neurons in gerbil

“…pressor levels of 40 to 80 dB SPL). A similar e¡ect has been shown at the level of the auditory nerve (Abbas and Sachs, 1976;Javel et al, 1978;Costalupes et al, 1987 ;Sokolowski et al, 1989;Delgutte, 1990), and also the basilar membrane, where 2TS originates (Ruggero et al, 1992 ;Rhode and Cooper, 1993;Cooper, 1996). However, two-tone rate level functions obtained using high level suppressors, exhibited a relatively shallow slope (refer to the curves corresponding to the 100 dB SPL suppressors in Fig.…”

Suppression of Auditory-Nerve-Fiber Responses to Off-CF Tones

“…Overall their data suggest that there is more suppression for tones above CF than at CF. Javel [5] presented rate-level functions for CF and off-CF tones with and without the same highside suppressor for one fiber. The data from that fiber showed more suppression for probe tones above CF than at CF.…”

“…Two-tone suppression has been extensively studied for probe tones at the characteristic frequency (CF) [e.g., 2,7]. However, there are only limited data on suppression of AN responses to probe tones at frequencies other than CF, i.e., at off-CF frequencies [1,5].…”