Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892.
J Neurosci. 2014 Mar 26;34(13):4665-76. doi: 10.1523/JNEUROSCI.3969-13.2014.
The mammalian auditory cortex integrates spectral and temporal acoustic features to support the perception of complex sounds, including conspecific vocalizations. Here we investigate coding of vocal stimuli in different subfields in macaque auditory cortex. We simultaneously measured auditory evoked potentials over a large swath of primary and higher order auditory cortex along the supratemporal plane in three animals chronically using high-density microelectrocorticographic arrays. To evaluate the capacity of neural activity to discriminate individual stimuli in these high-dimensional datasets, we applied a regularized multivariate classifier to evoked potentials to conspecific vocalizations. We found a gradual decrease in the level of overall classification performance along the caudal to rostral axis. Furthermore, the performance in the caudal sectors was similar across individual stimuli, whereas the performance in the rostral sectors significantly differed for different stimuli. Moreover, the information about vocalizations in the caudal sectors was similar to the information about synthetic stimuli that contained only the spectral or temporal features of the original vocalizations. In the rostral sectors, however, the classification for vocalizations was significantly better than that for the synthetic stimuli, suggesting that conjoined spectral and temporal features were necessary to explain differential coding of vocalizations in the rostral areas. We also found that this coding in the rostral sector was carried primarily in the theta frequency band of the response. These findings illustrate a progression in neural coding of conspecific vocalizations along the ventral auditory pathway.
哺乳动物听觉皮层整合了声音的频谱和时程特征，以支持对复杂声音的感知，包括同种动物的叫声。在这里，我们研究了猕猴听觉皮层不同亚区对声音刺激的编码。我们在三个动物的颞平面上使用高密度微电极皮质电图阵列，在较长的时间内同时测量初级和高级听觉皮层上的听觉诱发电位。为了评估神经活动在这些高维数据集中区分单个刺激的能力，我们将正则化多变量分类器应用于同种动物叫声的诱发电位。我们发现，沿着尾到头的轴，整体分类性能逐渐下降。此外，在尾部区域，个体刺激之间的性能相似，而在头部区域，不同刺激之间的性能显著不同。此外，尾部区域的叫声信息与仅包含原始叫声的频谱或时程特征的合成刺激的信息相似。然而，在头部区域，对叫声的分类明显优于对合成刺激的分类，这表明联合的频谱和时程特征对于解释头部区域对叫声的差异编码是必要的。我们还发现，这种在头部区域的编码主要发生在反应的 theta 频带中。这些发现说明了同种动物叫声在腹侧听觉通路上的神经编码逐渐进展。
