猫、猴和人类听觉皮层中复杂声音的处理

Processing of complex sounds in the auditory cortex of cat, monkey, and man.

作者信息

Rauschecker J P

机构信息

Georgetown Institute for Cognitive and Computational Sciences, Georgetown University Medical Center, Washington, DC, USA.

出版信息

Acta Otolaryngol Suppl. 1997;532:34-8. doi: 10.3109/00016489709126142.

Abstract

One of the fundamental features in the organization of sensory cortices which has emerged from 30 years of research in the visual system is the existence of multiple representation of the sensory world in the cerebral cortex. Compared with the visual system much less information exists about the functional specialization of multiple maps in the central auditory system. This is surprising, since an understanding of central auditory representations seems necessary for an understanding of higher auditory processing, including the perception of speech and the perception of auditory space. We have recorded single neuron activity in higher areas of auditory cortex of cats and rhesus monkeys. In cats, activity was recorded in the caudal part of the anterior ectosylvian (AE) cortex (areas AEA and AAF). More than half of the neurons were clearly tuned to the location of a sound source in azimuth and elevation. Frequency-modulated (FM) sounds elicited best responses at fast rates of modulation. By contrast, neurons in the posterior ectosylvian (PE) areas (PAF, VPAF) responded better to slow FM rates. This suggests a possible specialization for the processing of spatial attributes in the AE cortex, and a possible preference for auditory "patterns" in PE. In macaque monkeys, we explored the question of parallel processing in the higher auditory pathways by combining lesion and anatomical tracer techniques with single unit recording. Inactivation of primary auditory cortex (AI) abolished pure-tone responses in the caudomedial area (CM), but not in the rostral area (R). Injections of retrograde fluorescent tracers into R showed strong labeling of the main, ventral nucleus of the medial geniculate (MGv). Both findings suggest the existence of parallel pathways in the auditory cortex, originating at more peripheral sites and possibly specialized for the processing of auditory space vs. auditory patterns. The auditory pattern pathway in Macaque auditory cortex was further explored by using complex stimuli including Macaque-specific communication sounds. Neurons in the lateral belt areas (AL, ML, and CL) respond very selectively to bandpassed noise stimuli, to FM sounds of a certain rate and direction, as well as to certain classes of monkey calls. We are now in the process of exploring higher areas of human auditory cortex by measuring cortical activation with noninvasive functional magnetic resonance imaging (fMRI) while stimulating with complex auditory sounds.

摘要

在视觉系统30年的研究中所呈现出的感觉皮层组织的一个基本特征是,大脑皮层中存在对感觉世界的多种表征。与视觉系统相比,关于中枢听觉系统中多个图谱的功能特化的信息要少得多。这很令人惊讶,因为对于理解包括语音感知和听觉空间感知在内的高级听觉处理而言,对中枢听觉表征的理解似乎是必要的。我们记录了猫和恒河猴听觉皮层较高区域的单个神经元活动。在猫身上,在前外侧沟(AE)皮层的尾部区域(AEA和AAF区)记录到了活动。超过半数的神经元对声源在方位角和仰角上的位置有明显的调谐。调频(FM)声音在快速调制速率下引发最佳反应。相比之下,后外侧沟(PE)区域(PAF、VPAF)的神经元对较慢的FM速率反应更好。这表明AE皮层在处理空间属性方面可能存在特化,而PE区域可能更倾向于处理听觉“模式”。在猕猴中,我们通过将损伤和解剖示踪技术与单单元记录相结合,探讨了高级听觉通路中的并行处理问题。初级听觉皮层(AI)失活消除了尾内侧区域(CM)的纯音反应,但在嘴侧区域(R)没有。向R区注射逆行荧光示踪剂显示内侧膝状体主腹核(MGv)有强烈标记。这两个发现都表明听觉皮层中存在并行通路,这些通路起源于更外周的部位,可能分别专门用于处理听觉空间和听觉模式。通过使用包括猕猴特定交流声音在内的复杂刺激,进一步探索了猕猴听觉皮层中的听觉模式通路。外侧带区域(AL、ML和CL)的神经元对带通噪声刺激、特定速率和方向的FM声音以及特定类别的猴叫声有非常选择性的反应。我们现在正在通过在使用复杂听觉声音进行刺激的同时,用无创功能磁共振成像(fMRI)测量皮层激活来探索人类听觉皮层的更高区域。

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