School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas 75080, USA.
J Neurophysiol. 2013 Jul;110(1):177-89. doi: 10.1152/jn.00092.2013. Epub 2013 Apr 17.
Different speech sounds evoke unique patterns of activity in primary auditory cortex (A1). Behavioral discrimination by rats is well correlated with the distinctness of the A1 patterns evoked by individual consonants, but only when precise spike timing is preserved. In this study we recorded the speech-evoked responses in the primary, anterior, ventral, and posterior auditory fields of the rat and evaluated whether activity in these fields is better correlated with speech discrimination ability when spike timing information is included or eliminated. Spike timing information improved consonant discrimination in all four of the auditory fields examined. Behavioral discrimination was significantly correlated with neural discrimination in all four auditory fields. The diversity of speech responses across recordings sites was greater in posterior and ventral auditory fields compared with A1 and anterior auditor fields. These results suggest that, while the various auditory fields of the rat process speech sounds differently, neural activity in each field could be used to distinguish between consonant sounds with accuracy that closely parallels behavioral discrimination. Earlier observations in the visual and somatosensory systems that cortical neurons do not rely on spike timing should be reevaluated with more complex natural stimuli to determine whether spike timing contributes to sensory encoding.
不同的语音会在初级听觉皮层（A1）中引发独特的活动模式。大鼠的行为辨别与单个辅音引发的 A1 模式的清晰度密切相关，但只有在精确的尖峰时间得到保留的情况下才如此。在这项研究中，我们记录了大鼠初级、前、腹侧和后听觉区域的语音诱发反应，并评估了在包含或消除尖峰时间信息时，这些区域的活动是否与语音辨别能力更好地相关。尖峰时间信息提高了所有四个听觉区域的辅音辨别能力。行为辨别与所有四个听觉区域的神经辨别显著相关。与 A1 和前听觉区域相比，在后部和腹侧听觉区域，语音反应的多样性更大。这些结果表明，虽然大鼠的各种听觉区域对语音的处理方式不同，但每个区域的神经活动都可以用于准确区分辅音，其准确性与行为辨别非常接近。在视觉和躯体感觉系统中，皮质神经元不依赖于尖峰时间的早期观察结果应该用更复杂的自然刺激来重新评估，以确定尖峰时间是否有助于感觉编码。
