Fay R R, Edds-Walton P L
Parmly Hearing Institute and Department of Psychology, Loyola University Chicago, IL 60626, USA.
Hear Res. 1997 Nov;113(1-2):235-46. doi: 10.1016/s0378-5955(97)00148-2.
The frequency response of primary saccular afferents of toadfish (Opsanus tau) was studied in the time and frequency domains using the reverse correlation (revcor) method. Stimuli were noise bands with flat acceleration spectra delivered as whole-body motion. The recorded acceleration waveform was averaged over epochs preceding and following each spike. This average, termed the revcor, is an estimate of the response of an equivalent linear filter intervening between body motion and spike initiation. The spectrum of the revcor estimates the shape of the equivalent linear filter. Revcor responses were brief, damped oscillations indicative of relatively broadly tuned filters. Filter shapes were generally band-pass and differed in bandwidth, band edge slope, and characteristic frequency (74 Hz to 140 Hz). Filter shapes tend to be independent of stimulus level. Afferents can be placed into two groups with respect to characteristic frequency (74-88 Hz and 140 Hz). Some high-frequency afferents share a secondary peak at the characteristic frequency of low-frequency afferents, suggesting that an afferent may receive differently tuned peripheral inputs. For some afferents having similar filter shapes, revcor responses often differ only in polarity, probably reflecting inputs from hair cells oriented in opposite directions. The origin of frequency selectivity and its diversity among saccular afferents may arise from a combination of hair cell resonance and micromechanical processes. The resulting frequency analysis is the simplest yet observed among vertebrate animals. During courtship, male toadfish produce the 'boatwhistle' call, a periodic vocalization having several harmonics of a 130 Hz fundamental frequency. The saccule encodes the waveform of acoustic particle acceleration between < 50 and about 250 Hz. Thus, the fundamental frequency component of the boatwhistle is well encoded, but the successive higher harmonics are filtered out. The boatwhistle is thus encoded as a time-domain representation of its fundamental frequency or pulse repetition rate.
利用反向相关（revcor）方法，在时域和频域中研究了蟾鱼（Opsanus tau）初级球囊传入神经的频率响应。刺激是具有平坦加速度谱的噪声带，通过全身运动传递。在每个尖峰之前和之后的时间段内，对记录的加速度波形进行平均。这个平均值，称为revcor，是对介于身体运动和尖峰起始之间的等效线性滤波器响应的估计。revcor的频谱估计了等效线性滤波器的形状。Revcor响应是短暂的、衰减的振荡，表明滤波器的调谐相对较宽。滤波器形状通常为带通，在带宽、带边缘斜率和特征频率（74赫兹至140赫兹）方面有所不同。滤波器形状往往与刺激水平无关。就特征频率（74 - 88赫兹和140赫兹）而言，传入神经可分为两组。一些高频传入神经在低频传入神经的特征频率处有一个二次峰值，这表明一个传入神经可能接收不同调谐的外周输入。对于一些具有相似滤波器形状的传入神经，revcor响应通常仅在极性上有所不同，这可能反映了来自相反方向排列的毛细胞的输入。球囊传入神经中频率选择性及其多样性的起源可能源于毛细胞共振和微机械过程的组合。由此产生的频率分析是脊椎动物中观察到的最简单的分析。在求偶期间，雄性蟾鱼发出“船哨”叫声，这是一种具有130赫兹基频的几个谐波的周期性发声。球囊对50赫兹以下至约250赫兹之间的声粒子加速度波形进行编码。因此，“船哨”的基频分量得到了很好的编码，但后续的高次谐波被滤除。因此，“船哨”被编码为其基频或脉冲重复率的时域表示。
