Mountcastle V B, Steinmetz M A, Romo R
Philip Bard Laboratories of Neurophysiology, Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
J Neurosci. 1990 Sep;10(9):3032-44. doi: 10.1523/JNEUROSCI.10-09-03032.1990.
The capacities of humans and monkeys to discriminate between the frequencies of mechanical sinusoids delivered to the glabrous skin of the hand have been measured in psychophysical experiments. The 2 primates have similar capacities; they make discriminations with Weber fractions that change little over the frequency range from 20 to 200 Hz. The discriminatory capacities are similar whether stimuli are received passively or acquired actively. Combined experiments have been made in monkeys in which the electrical signs of the activity of quickly adapting (QA) and slowly adapting (SA) neurons of postcentral areas 3b and 1 were recorded, both in the working state as the animal made discriminations and in the irrelevant state in which the stimuli did not guide behavior. The neuronal responses were analyzed in terms of discharge rates, periodicities in the neuronal discharges, and harmonic contents. It was shown that discriminatory capacity depends upon the period lengths in the sets of periodically entrained activity evoked by stimuli readily discriminated, and not upon the small differences in rates of discharge evoked by those stimuli. The periodicities were shown by harmonic analysis to be sharply limited to stimulus frequencies. Low-frequency stimuli evoke periodicities at the second and third harmonics in some neurons, in addition to strongly periodic signals at the fundamental frequency of the stimuli. Their presence does not appear to interfere with frequency discrimination. Neuronal responses recorded in the stimulus-irrelevant state were not distinguishable from those recorded as monkeys made discriminations. The responses of SA neurons, recorded under similar conditions, resembled those of QA neurons in almost every feature, but reasons are given for concluding that the SA system plays no role in frequency discrimination in the sense of flutter.
在心理物理学实验中，已对人类和猴子辨别施加于手部无毛皮肤的机械正弦波频率的能力进行了测量。这两种灵长类动物具有相似的能力；它们以韦伯分数进行辨别，该分数在20至200赫兹的频率范围内变化不大。无论刺激是被动接受还是主动获取，其辨别能力都是相似的。在猴子身上进行了联合实验，记录了中央后回3b区和1区快速适应（QA）和缓慢适应（SA）神经元活动的电信号，记录过程既有动物进行辨别时的工作状态，也有刺激不引导行为的无关状态。从放电率、神经元放电的周期性和谐波含量方面对神经元反应进行了分析。结果表明，辨别能力取决于由易于辨别的刺激所诱发的周期性同步活动集合中的周期长度，而不取决于这些刺激所诱发的放电率的微小差异。通过谐波分析表明，这些周期性严格限于刺激频率。低频刺激除了在刺激的基频处产生强烈的周期性信号外，还会在一些神经元中诱发二次和三次谐波的周期性。它们的存在似乎并不干扰频率辨别。在刺激无关状态下记录的神经元反应与猴子进行辨别时记录的反应无法区分。在类似条件下记录的SA神经元的反应在几乎每个特征上都与QA神经元的反应相似，但给出了理由来得出结论，即SA系统在颤动意义上的频率辨别中不起作用。
