Auditory synapses to song premotor neurons are gated off during vocalization in zebra finches.
Auditory synapses to song premotor neurons are gated off during vocalization in zebra finches.
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DOI：
10.7554/elife.01833
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发表时间：
2014-02-18
期刊：
影响因子：
7.7
通讯作者：
Mooney R
中科院分区：
文献类型：
--
作者：
Hamaguchi K;Tschida KA;Yoon I;Donald BR;Mooney R
鸣禽使用听觉反馈来学习和维持它们的歌声，但反馈如何与发声运动回路相互作用仍不清楚。这种相互作用的一个潜在的网站是歌曲运动前核HVC，它接收听觉输入，并包含神经元（HVCX细胞），支配前前脑通路（AFP）重要的反馈依赖的声乐可塑性。虽然HVCX细胞的歌唱相关输出不会被扭曲的听觉反馈（英语：Distortious auditory feedback）改变，但震耳欲聋会逐渐削弱HVCX细胞上的突触，从而提高了它们在歌唱过程中仅在阈下水平整合反馈的可能性。使用唱歌斑胸草雀的细胞内录音，我们发现，尽管许多这些细胞在非唱歌状态下对听觉刺激做出反应，但HVCX细胞的唱歌相关突触活动未能受到干扰。此外，在体内多光子成像显示，脑缺血引起的HVCX突触的变化需要完整的AFP输出。这些发现支持了一个模型，其中AFP访问独立于HVC的反馈。DOI：http://dx.doi.org/10.7554/eLife.01833.001每当我们说话、唱歌或演奏乐器时，我们都会使用听觉反馈来微调我们的动作，以获得我们想要的声音。鸣禽也是用同样的过程来学习和保持它们的歌声。当幼鸟练习唱歌时，它们会将自己的声音与父亲的歌曲进行比较，这些歌曲之前已经存储在记忆中，并不断调整自己的歌曲，直到两个版本匹配。有人认为，听觉反馈与歌唱运动指令（来自大脑的指令，要求运动歌唱所需的肌肉）在鸣禽大脑的一个称为歌唱运动前核HVC的区域整合在一起。这个区域中的某些神经元（称为HVCX细胞）的结构在鸟类被刺激时迅速变化，这表明这些HVCX细胞检测到听觉反馈。Hamaguchi等人现在已经通过使用精细的电极记录雄性斑胸草雀唱歌时HVCX细胞中的信号来验证这一想法。每当鸟儿改变叫声时，这些细胞就会改变它们的活动模式。相比之下，当鸟儿在唱歌时听到自己的歌声的扭曲版本时，这些模式并没有改变。这表明HVCX细胞对听觉反馈不敏感，它们主要编码歌曲运动命令。如果HVCX细胞不检测反馈，那么为什么震耳欲聋会影响它们？HVCX细胞将信号间接发送到称为LMAN的大脑区域（这是前巢皮质外侧大细胞核的缩写）。通常情况下，如果一只鸟变聋了，它们的歌声质量就会开始下降，但这种下降可以通过破坏LMAN来防止。Hamaguchi等人使用高分辨率成像显示，破坏LMAN也可以防止震耳欲聋改变HVCX细胞的结构。这再次表明，听觉反馈不是从HVC传递到LMAN的;相反，信息流是在相反的方向上。这一令人惊讶的发现--即HVCX细胞不整合听觉反馈和歌曲运动指令--提出了一个问题，即大脑哪个区域实际上负责这一过程。需要进一步的实验来确定鸣禽大脑中的潜在电路。DOI：http://dx.doi.org/10.7554/eLife.01833.002网站
Songbirds use auditory feedback to learn and maintain their songs, but how feedback interacts with vocal motor circuitry remains unclear. A potential site for this interaction is the song premotor nucleus HVC, which receives auditory input and contains neurons (HVCX cells) that innervate an anterior forebrain pathway (AFP) important to feedback-dependent vocal plasticity. Although the singing-related output of HVCX cells is unaltered by distorted auditory feedback (DAF), deafening gradually weakens synapses on HVCX cells, raising the possibility that they integrate feedback only at subthreshold levels during singing. Using intracellular recordings in singing zebra finches, we found that DAF failed to perturb singing-related synaptic activity of HVCX cells, although many of these cells responded to auditory stimuli in non-singing states. Moreover, in vivo multiphoton imaging revealed that deafening-induced changes to HVCX synapses require intact AFP output. These findings support a model in which the AFP accesses feedback independent of HVC. DOI:http://dx.doi.org/10.7554/eLife.01833.001 Whenever we speak, sing, or play a musical instrument, we use auditory feedback to fine-tune our movements to achieve the sound that we want. This same process is used by songbirds to learn and maintain their songs. As juvenile birds practice singing, they compare their vocalizations with their father’s song, which they will previously have stored in memory, and continually tweak their own song until the two versions match. It has been suggested that auditory feedback is integrated with song motor commands—the instructions from the brain to move the muscles required for singing—in a region of the songbird brain called the song premotor nucleus HVC. The structure of certain neurons in this region, known as HVCX cells, rapidly changes when a bird is deafened, which suggests that these HVCX cells detect auditory feedback. Hamaguchi et al. have now tested this idea by using fine electrodes to record the signals in HVCX cells in male zebra finches as they sang. The cells changed their activity patterns whenever the birds changed their vocalizations. By contrast, these patterns did not change when the birds heard a distorted version of their own song played back to them as they sang. This suggests that HVCX cells are insensitive to auditory feedback, and that they mainly encode song motor commands instead. If HVCX cells don’t detect feedback, then why does deafening affect them? HVCX cells send signals indirectly to a brain region called the LMAN (which is short for the lateral magnocellular nucleus of the anterior nidopallium). Normally, if a bird becomes deaf, the quality of their song begins to deteriorate, but this deterioration can be prevented by destroying the LMAN. Hamaguchi et al. used high resolution imaging to show that destroying the LMAN also prevents deafening from altering the structure of HVCX cells. Again, this suggests that auditory feedback is not relayed from the HVC to the LMAN; instead the flow of information is in the opposite direction. This surprising finding—namely, that HVCX cells do not integrate auditory feedback and song motor commands—raises the question of which brain region is in fact responsible for this process. Further experiments will be required to identify the underlying circuitry in the brains of songbirds. DOI:http://dx.doi.org/10.7554/eLife.01833.002