Phillips D P, Orman S S
J Neurophysiol. 1984 Jan;51(1):147-63. doi: 10.1152/jn.1984.51.1.147.
In the auditory cortex of barbiturate-anesthetized cats, the posterior auditory field (field P) was identified by its tonotopic organization, and single neurons in that field were studied quantitatively for their sensitivity to the frequency and intensity of tonal stimuli presented via calibrated, sealed stimulating systems. Field P neurons had narrow, V-shaped, threshold frequency tuning curves. At suprathreshold levels, spike counts were generally greatest at frequencies at or close to the neuron's threshold best frequency (BF). Eighty-six percent of posterior-field neurons displayed spike counts that were a nonmonotonic function of the intensity of a BF tone. Of these, over 90% showed at least a 50% reduction in spike count at high stimulus levels, and almost 20% of nonmonotonic cells ceased responding entirely at high stimulus intensities. The nonmonotonic shape of spike count-versus-intensity profiles was typically preserved across the range of frequencies to which any given neuron was responsive. For some neurons, this had the consequence of generating a completely circumscribed frequency-intensity response area. That is, these neurons responded to a tonal stimulus only if the stimulus was within a restricted range of both frequency and intensity. These response areas showed internal organizations that appeared to reflect one or both of two processes. For some neurons, the optimal sound pressure level for spike counts varied with tone frequency, roughly paralleling the threshold tuning curve. For other neurons, the optimal sound pressure level tended to be constant across frequency despite threshold variations of up to 20 dB. The minimum response latencies of posterior-field neurons were generally in the range of 20-50 ms, while cells in the primary auditory cortex (AI) in the same animals generally had minimum latent periods of less than 20 ms. Comparison of these data with those previously presented for neurons in two other cortical auditory fields suggests that the cat's auditory cortex might show an interfield segregation of neurons according to their coding properties.
在巴比妥酸盐麻醉猫的听觉皮层中，通过其音频拓扑组织确定了后听觉场（P场），并对该场中的单个神经元对通过校准的密封刺激系统呈现的音调刺激的频率和强度的敏感性进行了定量研究。P场神经元具有狭窄的V形阈值频率调谐曲线。在阈上水平，放电计数通常在等于或接近神经元的阈值最佳频率（BF）的频率处最大。86%的后场神经元的放电计数是BF音调强度的非单调函数。其中，超过90%的神经元在高刺激水平下放电计数至少减少50%，近20%的非单调细胞在高刺激强度下完全停止反应。放电计数与强度曲线的非单调形状通常在任何给定神经元响应的频率范围内保持不变。对于一些神经元，这导致产生一个完全限定的频率-强度响应区域。也就是说，这些神经元仅在刺激处于频率和强度的受限范围内时才对音调刺激作出反应。这些响应区域显示出内部组织，似乎反映了两个过程中的一个或两个。对于一些神经元，放电计数的最佳声压级随音调频率而变化，大致与阈值调谐曲线平行。对于其他神经元，尽管阈值变化高达20 dB，但最佳声压级在频率范围内趋于恒定。后场神经元的最小反应潜伏期一般在20-50毫秒范围内，而同一动物初级听觉皮层（AI）中的细胞一般最小潜伏期小于20毫秒。将这些数据与先前针对其他两个皮层听觉场中的神经元呈现的数据进行比较表明，猫的听觉皮层可能根据其编码特性显示出神经元的场间分离。
