Margoliash D, Fortune E S
Department of Organismal Biology and Anatomy, University of Chicago, Illinois 60637.
J Neurosci. 1992 Nov;12(11):4309-26. doi: 10.1523/JNEUROSCI.12-11-04309.1992.
Song learning shapes the response properties of auditory neurons in the song system to become highly selective for the individual bird's own ("autogenous") song. The auditory representation of autogenous song is achieved in part by neurons that exhibit facilitated responses to combinations of components of song. To understand the circuits that underlie these complex properties, the combination sensitivity of single units in the hyperstriatum ventrale, pars caudale (HVc) of urethane-anesthetized zebra finches was studied. Some neurons exhibited nonlinear temporal summation, spectral summation, or both. The majority of these neurons exhibited low spontaneous rates and phasic responses. Most combination-sensitive neurons required highly accurate copies of sounds derived from the autogenous song and responded weakly to tone bursts, combinations of simple stimuli, or conspecific songs. Temporal combination-sensitive (TCS) neurons required either two or more segments of a single syllable, or two or more syllables of the autogenous song, to elicit a facilitated, excitatory response. TCS neurons integrated auditory input over periods ranging from 80 to 350 msec, although this represents a lower limit. Harmonic combination-sensitive (HCS) neurons required combinations of two harmonics with particular frequency and temporal characteristics that were similar to autogenous song syllables. Both TCS and HCS neurons responded much more weakly when the dynamical spectral features of the autogenous song or syllables were modified than when the dynamical amplitude (waveform) features of the songs were modified. These results suggest that understanding the temporal dynamics of auditory responses in HVc may provide insight into neuronal circuits modified by song learning.
鸣唱学习塑造了鸣唱系统中听觉神经元的反应特性，使其对个体鸟类自身（“自体的”）鸣唱具有高度选择性。自体鸣唱的听觉表征部分是由对鸣唱成分组合表现出易化反应的神经元实现的。为了理解这些复杂特性背后的神经回路，研究了乌拉坦麻醉的斑胸草雀腹侧尾端纹状体（HVc）中单个神经元的组合敏感性。一些神经元表现出非线性时间总和、频谱总和或两者兼有。这些神经元大多自发率低且呈相位反应。大多数对组合敏感的神经元需要来自自体鸣唱的高度精确的声音拷贝，对短音脉冲串、简单刺激组合或同种鸣唱反应较弱。时间组合敏感（TCS）神经元需要单个音节的两段或更多段，或自体鸣唱的两个或更多个音节，才能引发易化的兴奋性反应。TCS神经元在80至350毫秒的时间段内整合听觉输入，尽管这只是下限。谐波组合敏感（HCS）神经元需要两个具有特定频率和时间特征的谐波组合，这些特征类似于自体鸣唱音节。当自体鸣唱或音节的动态频谱特征被改变时，TCS和HCS神经元的反应都比歌曲的动态幅度（波形）特征被改变时弱得多。这些结果表明，了解HVc中听觉反应的时间动态可能有助于深入了解因鸣唱学习而改变的神经回路。
