Auditory nerve fiber response to wide-band noise and tone combinations

Abstract

1. Responses of single auditory nerve fibers to combinations of noise and tone were obtained. The results were found to depend on the relative effectiveness of each stimulus when presented alone. 2. When the response rate to one stimulus presented alone was considerably greater than the response rate to the other stimulus presented alone, the more effective stimulus dominated the responses when the two stimuli were combined. The more effective stimulus captured the response of the neuron. Thus, intense noise was found to mask responses to weaker tones, and intense tones were found to mask responses to weaker noise. This masking of the weaker stimulus is thought to enhance the signal-to-noise ratio of the most prominent response component. 3. When the two stimuli had similar effectiveness, complex interactions occurred. When the tone was near best (characteristic) frequency, partial summation effects occured. The tone partially suppressed the responses to the noise if other frequencies were used. Tones above best frequency caused particularly powerful suppression. 4. The bandwidth of the noise was varied somewhat. While bandwidth affected the effectiveness of the noise, it did not affect the types of interactions observed. 5. For a neuron which was essentially silent in the absence of acoustic stimuli, adding a weak level of noise lowered the threshold of responsiveness to the tone.

Predictions of formant-frequency discrimination in noise based on model auditory-nerve responses

“…Synchrony information is generally robust across a wide range of sound levels, even in response to signals in the presence of noise (Rhode et al, 1978). However, the temporal responses related to the envelope of the vowel complex would be expected to change as noise level increases, because the bandwidth of the peripheral filters increases with sound level and because adaptation shapes the responses of AN fibers.…”

Relations between frequency selectivity, temporal fine-structure processing, and speech reception in impaired hearing

“…The IPD thresholds and FMDTs were measured in quiet as well as in continuous noise backgrounds in order to test the robustness of the TFS processing to interfering noise. Physiological animal studies ͑e.g., Rhode et al, 1978;Abbas, 1981;Costalupes, 1985͒ have shown that phase locking to tones in the presence of background noise is generally preserved at SNRs near behavioral detection thresholds but ceases at sufficiently low SNRs. However, as no comparable studies exist in impaired hearing, it cannot be excluded that hearing impairment might potentiate the susceptibility of phase locking to noise disturbance.…”

Temporal Measures and Neural Strategies for Detection of Tones in Noise Based on Responses in Anteroventral Cochlear Nucleus

“…For auditory nerve (AN) fibers and most cochlear nucleus (CN) neurons, average discharge rate increases monotonically with tone level. However, the dynamic range of most AN fibers and CN neurons for rate encoding is significantly reduced by the presence of background noise (Geisler and Sinex 1980;Gibson et al 1985;Rhode et al 1978;Young and Barta 1986). This decrease is caused by a reduction in maximum rate at high tone levels and increased rates in response to the noise alone (Gibson et al 1985).…”

“…The most intensively studied temporal property is the synchronization coefficient of discharges to tone frequency, which has been shown to yield lower detection thresholds than discharge rates in both AN fibers (Rhode et al 1978) and CN neurons (Miller et al 1987) at relatively high noise levels. However, neural mechanisms that can extract phase-locking information for tone-in-noise detection are unclear.…”