Neural representations of temporally asymmetric stimuli in the auditory cortex of awake primates
Neural representations of temporally asymmetric stimuli in the auditory cortex of awake primates
复制标题
DOI：
10.1152/jn.2001.85.6.2364
复制
发表时间：
2001-06-01
影响因子：
2.5
通讯作者：
Wang, XQ
中科院分区：
文献类型：
--
作者：
Lu, T;Liang, L;Wang, XQ
听觉皮层对快速声瞬变的表征是一个尚未解决的基本问题。听觉皮层神经元的刺激同步反应有限，但人类和动物在辨别复杂声音的时间变化方面的感知表现比现有的神经生理学数据所预测的要好。本研究探讨了清醒状态下绒猴初级听觉皮层对时间不对称刺激的神经表征。刺激，斜坡和阻尼正弦曲线，系统地操纵（通过半衰期的指数包络）内的皮层神经元的假定的时间整合窗口。本研究的主要结果如下：（1）短周期（25 ms）的斜坡和阻尼窦状波的时间不对称性可以用平均放电率来反映，但不一定能用听皮层神经元的时间放电模式来反映。有相当大的反应特异性，这些刺激，使一些神经元强烈响应斜坡正弦曲线，但几乎完全没有反应，其阻尼对应，反之亦然。在181个神经元的研究中，140（77%）表现出显着的反应不对称性，在至少一个测试的半衰期值的指数包络。46个神经元在所有测试的半衰期内表现出显着的反应不对称性。持续放电通常在清醒条件下观察到，它导致许多神经元的反应不对称性比起始反应更大。2)更大比例的神经元（32/46），表现出显着的整体反应不对称性表现出更强的反应斜坡正弦波比阻尼正弦波，可能有助于这两类声音之间的感知响度的差异。3)神经元对斜坡或阻尼正弦曲线的不对称偏好似乎与其特征频率或最小响应潜伏期无关，这表明这是一种普遍存在于皮层神经元群体中的现象。此外，刺激的强度并没有显着的影响不对称偏好的测量基础上放电率。4)基于放电率的皮质神经元对时间不对称刺激的反应偏好的群体测量在性质上类似于人类听众在不同半衰期值下区分斜坡与阻尼正弦波的表现。这些研究结果表明，嵌入在复杂的声音中的快速声瞬变可以由皮质神经元的放电率来表示，而不是或在没有刺激同步放电的情况下。
The representation of rapid acoustic transients by the auditory cortex is a fundamental issue that is still unresolved. Auditory cortical neurons have been shown to be limited in their stimulus-synchronized responses, yet the perceptual performances of humans and animals in discriminating temporal variations in complex sounds are better than what existing neurophysiological data would predict. This study investigated the neural representation of temporally asymmetric stimuli in the primary auditory cortex of awake marmoset monkeys. The stimuli, ramped and damped sinusoids, were systematically manipulated (by means of half-life of the exponential envelope) within a cortical neuron's presumed temporal integration window. The main findings of this study are as follows: 1) temporal asymmetry in ramped and damped sinusoids with a short period (25 ms) was clearly reflected by average discharge rate but not necessarily by temporal discharge patterns of auditory cortical neurons. There was considerable response specificity to these stimuli such that some neurons were strongly responsive to a ramped sinusoid but almost completely unresponsive to its damped counterpart or vice versa. Of 181 neurons studied, 140 (77%) showed significant response asymmetry in at least one of the tested half-life values of the exponential envelope. Forty-six neurons showed significant response asymmetry over all half-lives tested. Sustained firing, commonly observed under awake conditions, contributed to greater response asymmetry than that of onset responses in many neurons. 2) A greater proportion of the neurons (32/46) that exhibited significant overall response asymmetry showed stronger responses to the ramped sinusoids than to the damped sinusoids, possibly contributing to the difference in the perceived loudness between these two classes of sounds. 3) The asymmetry preference of a neuron to ramped or damped sinusoids did not appear to be correlated with its characteristic frequency or minimum response latency, suggesting that this is a general phenomenon that exists across populations of cortical neurons. Moreover, the intensity of the stimuli did not have significant effects on the measure of the asymmetry preference based on discharge rate. 4) A population measure of response preference, based on discharge rate, of cortical neurons to the temporally asymmetric stimuli was qualitatively similar to the performance of human listeners in discriminating ramped versus damped sinusoids at different half-life values. These findings suggest that rapid acoustic transients embedded in complex sounds can be represented by discharge rates of cortical neurons instead of or in the absence of stimulus-synchronized discharges.