Department of Neuroscience, Georgetown University Medical Center, Washington, District of Columbia 20057, USA.
J Neurophysiol. 2012 Feb;107(4):1123-41. doi: 10.1152/jn.00793.2011. Epub 2011 Nov 30.
Auditory cortical processing is thought to be accomplished along two processing streams. The existence of a posterior/dorsal stream dealing, among others, with the processing of spatial aspects of sound has been corroborated by numerous studies in several species. An anterior/ventral stream for the processing of nonspatial sound qualities, including the identification of sounds such as species-specific vocalizations, has also received much support. Originally discovered in anterolateral belt cortex, most recent work on the anterior/ventral pathway has been performed on far anterior superior temporal (ST) areas and on ventrolateral prefrontal cortex (VLPFC). Regions of the anterior/ventral stream near its origin in early auditory areas have been less explored. In the present study, we examined three early auditory regions with different anteroposterior locations (caudal, middle, and rostral) in awake rhesus macaques. We analyzed how well classification based on sound-evoked activity patterns of neuronal populations replicates the original stimulus categories. Of the three regions, the rostral region (rR), which included core area R and medial belt area RM, yielded the greatest classification success across all stimulus classes or between classes of natural sounds. Starting from ∼80 ms past stimulus onset, clustering based on the population response in rR became clearly more successful than clustering based on responses from any other region. Our study demonstrates that specialization for sound-identity processing can be found very early in the auditory ventral stream. Furthermore, the fact that this processing develops over time can shed light on underlying mechanisms. Finally, we show that population analysis is a more sensitive method for revealing functional specialization than conventional types of analysis.
听觉皮层处理被认为是沿着两条处理流完成的。大量的研究在多个物种中证实了存在一条后/背侧处理流,用于处理声音的空间方面,包括物种特异性发声等。另一条前/腹侧处理流用于处理非空间声音特征,包括识别声音,如物种特异性发声。这条前/腹侧通路最初在外侧带皮层中被发现,最近关于前/腹侧通路的大部分工作都集中在前上颞叶(ST)的远前区域和腹侧前额叶皮层(VLPFC)上。在前/腹侧通路起源的早期听觉区域附近的区域探索较少。在本研究中,我们在清醒的恒河猴中检查了三个具有不同前后位置(尾侧、中间和额侧)的早期听觉区域。我们分析了基于神经元群体活动模式的分类在多大程度上复制了原始刺激类别。在三个区域中,包括核心区 R 和内侧带区 RM 的额侧区域(rR)在所有刺激类别或自然声音类别之间的分类成功率最高。从刺激开始后约 80 毫秒开始,基于 rR 群体反应的聚类明显比基于任何其他区域反应的聚类更成功。我们的研究表明,声音身份处理的专业化可以在听觉腹侧流中很早就出现。此外,随着时间的推移,这种处理的发展可以揭示潜在的机制。最后,我们表明,与传统类型的分析相比,群体分析是一种更敏感的方法,可以揭示功能专业化。
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