Frisina R D, Smith R L, Chamberlain S C
Otolaryngology Division of Surgery Department, University of Rochester School of Medicine, New York 14642.
Hear Res. 1990 Mar;44(2-3):99-122. doi: 10.1016/0378-5955(90)90074-y.
The main goal of the present study was to investigate the encoding of a biologically-relevant acoustic feature--amplitude modulation (AM)--in single neurons of the auditory nerve and ventral cochlear nucleus (VCN). In the anesthetized gerbil auditory-nerve fibers and VCN units show strong synchronous responses to low-intensity, low-frequency AM. As frequency increases, the strength of the synchronous response decreases. In the auditory nerve the strength of the synchronous response is substantially less at high intensities than at low intensities and does not change significantly with AM frequency at high intensities. In contrast to the auditory nerve, VCN units show strong responses at high intensities. They have a particular AM frequency to which they are maximally responsive, and this frequency varies from unit to unit. Therefore, VCN units transform their ascending inputs by enhancing the synchronous response to AM. A correlation exists between a unit's ability to encode AM and its responses to simple sounds. Specifically, onset units show the strongest synchronous responses, followed in order by chopper, primarylike-with-notch and primarylike units. This enhancement is greatest at high intensities and can occur up to 90 dB above a unit's threshold. Thus, a hierarchy of enhancement for AM processing exists in the most peripheral nucleus of the central auditory system.
本研究的主要目的是研究一种与生物学相关的声学特征——幅度调制（AM）——在听神经和耳蜗腹侧核（VCN）单个神经元中的编码情况。在麻醉的沙鼠中，听神经纤维和VCN单元对低强度、低频AM表现出强烈的同步反应。随着频率增加，同步反应的强度降低。在听神经中，高强度时同步反应的强度明显低于低强度时，且在高强度时同步反应强度随AM频率变化不显著。与听神经不同，VCN单元在高强度时表现出强烈反应。它们有一个对其反应最大的特定AM频率，且该频率因单元而异。因此，VCN单元通过增强对AM的同步反应来转换其上行输入。单元编码AM的能力与其对简单声音的反应之间存在相关性。具体而言，起始单元表现出最强的同步反应，其次依次是斩波单元、带凹口的初级样单元和初级样单元。这种增强在高强度时最大，且可在比单元阈值高90 dB时出现。因此，在中枢听觉系统最外周的核中存在AM处理增强的层级结构。
