Keilson S E, Richards V M, Wyman B T, Young E D
Center for Hearing Sciences, Johns Hopkins University, Baltimore, Maryland 21205, USA.
J Acoust Soc Am. 1997 Aug;102(2 Pt 1):1056-71. doi: 10.1121/1.419859.
Chopper units of the ventral cochlear nucleus (VCN) provide a rare representation of stimulus spectrum and a temporal representation of fundamental frequency (F0). This dual representation may be useful in segregating competing speech sounds, where differences in F0 are a cue. Responses to the vowel portion of concurrently presented pairs of syllables /bV integral/ with different F0's (88, 98, and 112 Hz) were studied in the VCN of anesthetized cats; 11 English vowels were used for V. Vowels were chosen so that one had a formant frequency just above the unit's best frequency (BF) and the other had a formant just below BF. By changing the stimulus sampling rate, formant peaks were shifted relative to the unit's BF, producing a range of stimuli, varying in the relative power of the two vowels within the unit's tuning curve. Results show that units' discharge rates reflect the energy within their tuning curves and the relative synchronization of units' responses to the two F0's favors the dominant vowel. A method of segregating two vowels is provided in which relative synchronization to the F0's is used to apportion discharge rate between the vowels. Best results were obtained in chopper units, although primarylike units showed similar behavior.
腹侧耳蜗核（VCN）的切碎器单元提供了刺激频谱的罕见表示以及基频（F0）的时间表示。这种双重表示可能有助于分离相互竞争的语音，其中F0的差异是一个线索。在麻醉猫的VCN中研究了对同时呈现的具有不同F0（88、98和112 Hz）的音节对/bV积分/的元音部分的反应；V使用了11个英语元音。选择元音时，一个元音的共振峰频率刚好高于单元的最佳频率（BF），另一个元音的共振峰刚好低于BF。通过改变刺激采样率，共振峰峰值相对于单元的BF发生偏移，从而产生一系列刺激，在单元调谐曲线内两个元音的相对功率有所不同。结果表明，单元的放电率反映了其调谐曲线内的能量，并且单元对两个F0的反应的相对同步性有利于占主导地位的元音。提供了一种分离两个元音的方法，其中利用与F0的相对同步性在元音之间分配放电率。尽管初级样单元表现出类似的行为，但在切碎器单元中获得了最佳结果。
